Merge branch 'develop' into update_android_doc

.pre-commit-config.yaml

@@ -31,6 +31,3 @@
     -   id: go-fmt
         types:
         - go
-    -   id: gometalinter
-        types:
-        - go

CMakeLists.txt

@@ -86,6 +86,14 @@ if(ANDROID OR IOS)
         "Disable MKLDNN when cross-compiling for Android and iOS" FORCE)
     set(WITH_MKLML OFF CACHE STRING
         "Disable MKLML package when cross-compiling for Android and iOS" FORCE)
+
+    # Compile PaddlePaddle mobile inference library
+    if (NOT WITH_C_API)
+        set(WITH_C_API ON CACHE STRING
+            "Always compile the C_API when cross-compiling for Android and iOS" FORCE)
+    endif()
+    set(MOBILE_INFERENCE ON)
+    add_definitions(-DPADDLE_MOBILE_INFERENCE)
 endif()
 
 set(THIRD_PARTY_PATH "${CMAKE_BINARY_DIR}/third_party" CACHE STRING
@@ -97,6 +105,12 @@ if (WITH_C_API AND WITH_PYTHON)
     "different Python interpreter from compiling.")
 endif()
 
+if(MOBILE_INFERENCE)
+    set(THIRD_PARTY_BUILD_TYPE MinSizeRel)
+else()
+    set(THIRD_PARTY_BUILD_TYPE Release)
+endif()
+
 ########################################################################################
 
 include(external/mklml)     # download mklml package
@@ -160,9 +174,11 @@ endif(USE_NNPACK)
 
 add_subdirectory(proto)
 
-# "add_subdirectory(go)" should be placed after the following loine,
-# because it depends on paddle/optimizer.
-add_subdirectory(paddle/optimizer)
+if(NOT MOBILE_INFERENCE)
+    # "add_subdirectory(go)" should be placed after the following loine,
+    # because it depends on paddle/optimizer.
+    add_subdirectory(paddle/optimizer)
+endif()
 
 # "add_subdirectory(paddle)" and "add_subdirectory(python)" should be
 # placed after this block, because they depends on it.

README.md

@@ -51,19 +51,19 @@ Please refer to our [release announcement](https://github.com/PaddlePaddle/Paddl
 - **Connected to Products**
 
     In addition, PaddlePaddle is also designed to be easily deployable. At Baidu,
-    PaddlePaddle has been deployed into products or service with a vast number
+    PaddlePaddle has been deployed into products and services with a vast number
     of users, including ad click-through rate (CTR) prediction, large-scale image
     classification, optical character recognition(OCR), search ranking, computer
     virus detection, recommendation, etc. It is widely utilized in products at
-    Baidu and it has achieved a significant impact. We hope you can also exploit
-    the capability of PaddlePaddle to make a huge impact for your product.
+    Baidu and it has achieved a significant impact. We hope you can also explore
+    the capability of PaddlePaddle to make an impact on your product.
 
 ## Installation
 
 It is recommended to check out the
 [Docker installation guide](http://doc.paddlepaddle.org/develop/doc/getstarted/build_and_install/docker_install_en.html)
 before looking into the
-[build from source guide](http://doc.paddlepaddle.org/develop/doc/getstarted/build_and_install/build_from_source_en.html)
+[build from source guide](http://doc.paddlepaddle.org/develop/doc/getstarted/build_and_install/build_from_source_en.html).
 
 ## Documentation
 
@@ -72,7 +72,7 @@ We provide [English](http://doc.paddlepaddle.org/develop/doc/) and
 
 - [Deep Learning 101](http://book.paddlepaddle.org/index.html)
 
-  You might want to start from this online interactive book that can run in Jupyter Notebook.
+  You might want to start from this online interactive book that can run in a Jupyter Notebook.
 
 - [Distributed Training](http://doc.paddlepaddle.org/develop/doc/howto/usage/cluster/cluster_train_en.html)
 

benchmark/paddle/image/run_mkldnn.sh

 set -e
 
-unset OMP_NUM_THREADS MKL_NUM_THREADS
-export OMP_DYNAMIC="FALSE"
-export KMP_AFFINITY="granularity=fine,compact,0,0"
-
 function train() {
+  unset OMP_NUM_THREADS MKL_NUM_THREADS
+  export OMP_DYNAMIC="FALSE"
+  export KMP_AFFINITY="granularity=fine,compact,0,0"
   topology=$1
   bs=$2
   use_mkldnn=$3
   if [ $3 == "True" ]; then
-    use_mkldnn=$3
     thread=1
     log="logs/${topology}-mkldnn-${bs}.log"
   elif [ $3 == "False" ]; then
-    use_mkldnn=$3
     thread=`nproc`
+    # each trainer_count use only 1 core to avoid conflict
+    export OMP_NUM_THREADS=1
+    export MKL_NUM_THREADS=1
     log="logs/${topology}-${thread}mklml-${bs}.log"
   else
     echo "Wrong input $3, use True or False."
+    exit 0
   fi
   args="batch_size=${bs}"
   config="${topology}.py"
@@ -39,8 +40,7 @@ if [ ! -d "logs" ]; then
   mkdir logs
 fi
 
-#========= mkldnn =========#
-# vgg
+#========== mkldnn ==========#
 train vgg 64 True
 train vgg 128 True
 train vgg 256 True

cmake/configure.cmake

@@ -24,6 +24,10 @@ if(WITH_DOUBLE)
     add_definitions(-DPADDLE_TYPE_DOUBLE)
 endif(WITH_DOUBLE)
 
+if(WITH_TESTING)
+    add_definitions(-DPADDLE_WITH_TESTING)
+endif(WITH_TESTING)
+
 if(NOT WITH_TIMER)
     add_definitions(-DPADDLE_DISABLE_TIMER)
 endif(NOT WITH_TIMER)
@@ -49,11 +53,12 @@ if(NOT WITH_GOLANG)
 endif(NOT WITH_GOLANG)
 
 if(NOT WITH_GPU)
-    add_definitions(-DPADDLE_ONLY_CPU)
     add_definitions(-DHPPL_STUB_FUNC)
 
     list(APPEND CMAKE_CXX_SOURCE_FILE_EXTENSIONS cu)
 else()
+    add_definitions(-DPADDLE_WITH_CUDA)
+
     FIND_PACKAGE(CUDA REQUIRED)
 
     if(${CUDA_VERSION_MAJOR} VERSION_LESS 7)

cmake/external/eigen.cmake

@@ -8,7 +8,7 @@ ExternalProject_Add(
     extern_eigen3
     ${EXTERNAL_PROJECT_LOG_ARGS}
     GIT_REPOSITORY  "https://github.com/RLovelett/eigen.git"
-    GIT_TAG         "master"
+    GIT_TAG         4e79cb69b9425f5f8c3a84be4350d4ab75b5fd9d
     PREFIX          ${EIGEN_SOURCE_DIR}
     UPDATE_COMMAND  ""
     CONFIGURE_COMMAND ""

cmake/external/gflags.cmake

@@ -36,6 +36,7 @@ ExternalProject_Add(
     # change this back to the official Github repo once my PR is
     # merged.
     GIT_REPOSITORY  "https://github.com/wangkuiyi/gflags.git"
+    GIT_TAG         986964c07427ecb9cdb5bd73f73ebbd40e54dadb
     PREFIX          ${GFLAGS_SOURCES_DIR}
     UPDATE_COMMAND  ""
     CMAKE_ARGS      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
@@ -45,11 +46,11 @@ ExternalProject_Add(
                     -DCMAKE_INSTALL_PREFIX=${GFLAGS_INSTALL_DIR}
                     -DCMAKE_POSITION_INDEPENDENT_CODE=ON
                     -DBUILD_TESTING=OFF
-                    -DCMAKE_BUILD_TYPE=Release
+                    -DCMAKE_BUILD_TYPE=${THIRD_PARTY_BUILD_TYPE}
                     ${EXTERNAL_OPTIONAL_ARGS}
     CMAKE_CACHE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=${GFLAGS_INSTALL_DIR}
                      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
-                     -DCMAKE_BUILD_TYPE:STRING=Release
+                     -DCMAKE_BUILD_TYPE:STRING=${THIRD_PARTY_BUILD_TYPE}
 )
 
 ADD_LIBRARY(gflags STATIC IMPORTED GLOBAL)

cmake/external/glog.cmake

@@ -31,6 +31,7 @@ ExternalProject_Add(
     ${EXTERNAL_PROJECT_LOG_ARGS}
     DEPENDS gflags
     GIT_REPOSITORY  "https://github.com/google/glog.git"
+    GIT_TAG         v0.3.5
     PREFIX          ${GLOG_SOURCES_DIR}
     UPDATE_COMMAND  ""
     CMAKE_ARGS      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
@@ -43,12 +44,12 @@ ExternalProject_Add(
                     -DWITH_GFLAGS=ON
                     -Dgflags_DIR=${GFLAGS_INSTALL_DIR}/lib/cmake/gflags
                     -DBUILD_TESTING=OFF
-                    -DCMAKE_BUILD_TYPE=Release
+                    -DCMAKE_BUILD_TYPE=${THIRD_PARTY_BUILD_TYPE}
                     ${EXTERNAL_OPTIONAL_ARGS}
     CMAKE_CACHE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=${GLOG_INSTALL_DIR}
                      -DCMAKE_INSTALL_LIBDIR:PATH=${GLOG_INSTALL_DIR}/lib
                      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
-                     -DCMAKE_BUILD_TYPE:STRING=Release
+                     -DCMAKE_BUILD_TYPE:STRING=${THIRD_PARTY_BUILD_TYPE}
 )
 
 ADD_LIBRARY(glog STATIC IMPORTED GLOBAL)

cmake/external/gtest.cmake

@@ -56,11 +56,11 @@ IF(WITH_TESTING)
                         -DBUILD_GMOCK=ON
                         -Dgtest_disable_pthreads=ON
                         -Dgtest_force_shared_crt=ON
-                        -DCMAKE_BUILD_TYPE=Release
+                        -DCMAKE_BUILD_TYPE=${THIRD_PARTY_BUILD_TYPE}
                         ${EXTERNAL_OPTIONAL_ARGS}
         CMAKE_CACHE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=${GTEST_INSTALL_DIR}
                          -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
-                         -DCMAKE_BUILD_TYPE:STRING=Release
+                         -DCMAKE_BUILD_TYPE:STRING=${THIRD_PARTY_BUILD_TYPE}
     )
 
     ADD_LIBRARY(gtest STATIC IMPORTED GLOBAL)

cmake/external/protobuf.cmake

@@ -191,12 +191,12 @@ FUNCTION(build_protobuf TARGET_NAME BUILD_FOR_HOST)
             ${OPTIONAL_ARGS}
             -Dprotobuf_BUILD_TESTS=OFF
             -DCMAKE_POSITION_INDEPENDENT_CODE=ON
-            -DCMAKE_BUILD_TYPE=Release
+            -DCMAKE_BUILD_TYPE=${THIRD_PARTY_BUILD_TYPE}
             -DCMAKE_INSTALL_PREFIX=${PROTOBUF_INSTALL_DIR}
             -DCMAKE_INSTALL_LIBDIR=lib
         CMAKE_CACHE_ARGS
             -DCMAKE_INSTALL_PREFIX:PATH=${PROTOBUF_INSTALL_DIR}
-            -DCMAKE_BUILD_TYPE:STRING=Release
+            -DCMAKE_BUILD_TYPE:STRING=${THIRD_PARTY_BUILD_TYPE}
             -DCMAKE_VERBOSE_MAKEFILE:BOOL=OFF
             -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
             ${OPTIONAL_CACHE_ARGS}

cmake/external/warpctc.cmake

@@ -35,6 +35,7 @@ ExternalProject_Add(
     extern_warpctc
     ${EXTERNAL_PROJECT_LOG_ARGS}
     GIT_REPOSITORY  "https://github.com/gangliao/warp-ctc.git"
+    GIT_TAG         b63a0644654a3e0ed624c85a1767bc8193aead09
     PREFIX          ${WARPCTC_SOURCES_DIR}
     UPDATE_COMMAND  ""
     CMAKE_ARGS      -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
@@ -48,9 +49,9 @@ ExternalProject_Add(
                     -DCMAKE_DISABLE_FIND_PACKAGE_Torch=ON
                     -DBUILD_SHARED=ON
                     -DCMAKE_POSITION_INDEPENDENT_CODE=ON
-                    -DCMAKE_BUILD_TYPE=Release
+                    -DCMAKE_BUILD_TYPE=${THIRD_PARTY_BUILD_TYPE}
                     ${EXTERNAL_OPTIONAL_ARGS}
-    CMAKE_CACHE_ARGS -DCMAKE_BUILD_TYPE:STRING=Release
+    CMAKE_CACHE_ARGS -DCMAKE_BUILD_TYPE:STRING=${THIRD_PARTY_BUILD_TYPE}
                      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
                      -DCMAKE_INSTALL_PREFIX:PATH=${WARPCTC_INSTALL_DIR}
 )

cmake/external/zlib.cmake

@@ -42,11 +42,11 @@ ExternalProject_Add(
                     -DBUILD_SHARED_LIBS=OFF
                     -DCMAKE_POSITION_INDEPENDENT_CODE=ON
                     -DCMAKE_MACOSX_RPATH=ON
-                    -DCMAKE_BUILD_TYPE=Release
+                    -DCMAKE_BUILD_TYPE=${THIRD_PARTY_BUILD_TYPE}
                     ${EXTERNAL_OPTIONAL_ARGS}
     CMAKE_CACHE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=${ZLIB_INSTALL_DIR}
                      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
-                     -DCMAKE_BUILD_TYPE:STRING=Release
+                     -DCMAKE_BUILD_TYPE:STRING=${THIRD_PARTY_BUILD_TYPE}
 )
 
 LIST(APPEND external_project_dependencies zlib)

cmake/generic.cmake

@@ -389,13 +389,60 @@ function(go_test TARGET_NAME)
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
 endfunction(go_test)
 
+# Modification of standard 'protobuf_generate_cpp()' with protobuf-lite support
+# Usage:
+#   paddle_protobuf_generate_cpp(<proto_srcs> <proto_hdrs> <proto_files>)
+
+function(paddle_protobuf_generate_cpp SRCS HDRS)
+  if(NOT ARGN)
+    message(SEND_ERROR "Error: paddle_protobuf_generate_cpp() called without any proto files")
+    return()
+  endif()
+
+  set(${SRCS})
+  set(${HDRS})
+
+  if (MOBILE_INFERENCE)
+      set(EXTRA_FLAG "lite:")  
+  else()
+      set(EXTRA_FLAG "") 
+  endif()
+
+  foreach(FIL ${ARGN})
+    get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
+    get_filename_component(FIL_WE ${FIL} NAME_WE)
+    
+    set(_protobuf_protoc_src "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.cc")
+    set(_protobuf_protoc_hdr "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.h")
+    list(APPEND ${SRCS} "${_protobuf_protoc_src}")
+    list(APPEND ${HDRS} "${_protobuf_protoc_hdr}")
+    
+    add_custom_command(
+      OUTPUT "${_protobuf_protoc_src}"
+             "${_protobuf_protoc_hdr}"
+
+      COMMAND ${CMAKE_COMMAND} -E make_directory "${CMAKE_CURRENT_BINARY_DIR}"
+      COMMAND ${PROTOBUF_PROTOC_EXECUTABLE} 
+      -I${CMAKE_CURRENT_SOURCE_DIR}
+      --cpp_out "${EXTRA_FLAG}${CMAKE_CURRENT_BINARY_DIR}" ${ABS_FIL}
+      DEPENDS ${ABS_FIL} protoc
+      COMMENT "Running C++ protocol buffer compiler on ${FIL}"
+      VERBATIM )
+  endforeach()
+
+  set_source_files_properties(${${SRCS}} ${${HDRS}} PROPERTIES GENERATED TRUE)
+  set(${SRCS} ${${SRCS}} PARENT_SCOPE)
+  set(${HDRS} ${${HDRS}} PARENT_SCOPE)
+endfunction()
+
+
 function(proto_library TARGET_NAME)
   set(oneValueArgs "")
   set(multiValueArgs SRCS DEPS)
   cmake_parse_arguments(proto_library "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
   set(proto_srcs)
   set(proto_hdrs)
-  protobuf_generate_cpp(proto_srcs proto_hdrs ${proto_library_SRCS})
+  paddle_protobuf_generate_cpp(proto_srcs proto_hdrs ${proto_library_SRCS})
   cc_library(${TARGET_NAME} SRCS ${proto_srcs} DEPS ${proto_library_DEPS} protobuf)
 endfunction()
 

cmake/util.cmake

@@ -73,6 +73,23 @@ function(link_paddle_exe TARGET_NAME)
         generate_rdma_links()
     endif()
 
+    if(MOBILE_INFERENCE)
+        target_circle_link_libraries(${TARGET_NAME}
+            ARCHIVE_START
+            paddle_gserver
+            paddle_function
+            ARCHIVE_END
+            paddle_math
+            paddle_utils
+            paddle_parameter
+            paddle_proto
+            paddle_cuda
+            ${EXTERNAL_LIBS}
+            ${CMAKE_THREAD_LIBS_INIT}
+            ${CMAKE_DL_LIBS}
+            ${RDMA_LD_FLAGS}
+            ${RDMA_LIBS})
+    else()
         target_circle_link_libraries(${TARGET_NAME}
             ARCHIVE_START
             paddle_gserver
@@ -92,6 +109,7 @@ function(link_paddle_exe TARGET_NAME)
             ${CMAKE_DL_LIBS}
             ${RDMA_LD_FLAGS}
             ${RDMA_LIBS})
+    endif()
 
     if(ANDROID)
         target_link_libraries(${TARGET_NAME} log)

doc/api/v2/config/layer.rst

@@ -345,6 +345,11 @@ clip
 ..  autoclass:: paddle.v2.layer.clip
     :noindex:
 
+resize
+------
+..  autoclass:: paddle.v2.layer.resize
+    :noindex:
+
 slope_intercept
 ---------------
 ..  autoclass:: paddle.v2.layer.slope_intercept

doc/api/v2/config/networks.rst

@@ -125,3 +125,8 @@ simple_attention
     :members: simple_attention
     :noindex:
 
+dot_product_attention
+---------------------
+..  automodule:: paddle.v2.networks
+    :members: dot_product_attention
+    :noindex:

doc/design/block.md

@@ -5,12 +5,12 @@
 Both deep learning systems and programming languages help users describe computation procedures.  These systems use various representations of computation:
 
 - Caffe, Torch, and Paddle: sequences of layers.
-- TensorFlow, Caffe2, Mxnet: graphs of operators.
+- TensorFlow, Caffe2, Mxnet: graph of operators.
 - PaddlePaddle: nested blocks, like C++ and Java programs.
 
 ## Block in Programming Languages and Deep Learning
 
-In programming languages, a block is a pair of curly braces that includes local variables definitions and a sequence of instructions, or operators.
+In programming languages, a block is a pair of curly braces that includes local variables definitions and a sequence of instructions or operators.
 
 Blocks work with control flow structures like `if`, `else`, and `for`, which have equivalents in deep learning:
 
@@ -24,14 +24,14 @@ A key difference is that a C++ program describes a one pass computation, whereas
 
 ## Stack Frames and the Scope Hierarchy
 
-The existence of the backward makes the execution of a block of traditional programs and PaddlePaddle different to each other:
+The existence of the backward pass makes the execution of a block of PaddlePaddle different from traditional programs:
 
 | programming languages | PaddlePaddle                    |
-|-----------------------|-------------------------------|
+|-----------------------|---------------------------------|
 | stack                 | scope hierarchy                 |
 | stack frame           | scope                           |
 | push at entering block| push at entering block          |
-| pop at leaving block  | destroy at minibatch completes|
+| pop at leaving block  | destroy when minibatch completes|
 
 1. In traditional programs:
 
@@ -42,9 +42,9 @@ The existence of the backward makes the execution of a block of traditional prog
 1. In PaddlePaddle
 
    - When the execution enters a block, PaddlePaddle adds a new scope, where it realizes variables.
-   - PaddlePaddle doesn't pop a scope after the execution of the block because variables therein are to be used by the backward pass.  So it has a stack forest known as a *scope hierarchy*.
+   - PaddlePaddle doesn't pop a scope after the execution of the block because variables therein are used by the backward pass.  So it has a stack forest known as a *scope hierarchy*.
    - The height of the highest tree is the maximum depth of nested blocks.
-   - After the process of a minibatch, PaddlePaddle destroys the scope hierarchy.
+   - After the processing of a minibatch, PaddlePaddle destroys the scope hierarchy.
 
 ## Use Blocks in C++ and PaddlePaddle Programs
 
@@ -55,17 +55,23 @@ Let us consolidate the discussion by presenting some examples.
 The following C++ programs shows how blocks are used with the `if-else` structure:
 
 ```c++
+namespace pd = paddle;
+
 int x = 10;
-int y = 20;
-int out;
+int y = 1;
+int z = 10;
 bool cond = false;
+int o1, o2;
 if (cond) {
   int z = x + y;
-  out = softmax(z);
+  o1 = z;
+  o2 = pd::layer::softmax(z);
 } else {
-  int z = fc(x);
-  out = z;
+  int d = pd::layer::fc(z);
+  o1 = d;
+  o2 = d+1;
 }
+
 ```
 
 An equivalent PaddlePaddle program from the design doc of the [IfElseOp operator](./if_else_op.md) is as follows:
@@ -73,57 +79,55 @@ An equivalent PaddlePaddle program from the design doc of the [IfElseOp operator
 ```python
 import paddle as pd
 
-x = var(10)
-y = var(20)
-cond = var(false)
-ie = pd.create_ifelseop(inputs=[x], output_num=1)
+x = minibatch([10, 20, 30]) # shape=[None, 1]
+y = var(1) # shape=[1], value=1
+z = minibatch([10, 20, 30]) # shape=[None, 1]
+cond = larger_than(x, 15) # [false, true, true]
+
+ie = pd.ifelse()
 with ie.true_block():
-    x = ie.inputs(true, 0)
-    z = operator.add(x, y)
-    ie.set_output(true, 0, operator.softmax(z))
+    d = pd.layer.add_scalar(x, y)
+    ie.output(d, pd.layer.softmax(d))
 with ie.false_block():
-    x = ie.inputs(false, 0)
-    z = layer.fc(x)
-    ie.set_output(true, 0, operator.softmax(z))
-out = b(cond)
+    d = pd.layer.fc(z)
+    ie.output(d, d+1)
+o1, o2 = ie(cond)
 ```
 
-In both examples, the left branch computes `softmax(x+y)` and the right branch computes `fc(x)`.
+In both examples, the left branch computes `x+y` and `softmax(x+y)`, the right branch computes `fc(x)` and `x+1` .
+
+The difference is that variables in the C++ program contain scalar values, whereas those in the PaddlePaddle programs are mini-batches of instances.
 
-A difference is that variables in the C++ program contain scalar values, whereas those in the PaddlePaddle programs are mini-batches of instances.  The `ie.input(true, 0)` invocation returns instances in the 0-th input, `x`, that corresponds to true values in `cond` as the local variable `x`, where `ie.input(false, 0)` returns instances corresponding to false values.
 
 ### Blocks with `for` and `RNNOp`
 
-The following RNN model from the [RNN design doc](./rnn.md)
+The following RNN model in PaddlePaddle from the [RNN design doc](./rnn.md) :
 
 ```python
-x = sequence([10, 20, 30])
-m = var(0)
-W = tensor()
-U = tensor()
-
-rnn = create_rnn(inputs=[input])
-with rnn.stepnet() as net:
-  x = net.set_inputs(0)
-  h = net.add_memory(init=m)
-  fc_out = pd.matmul(W, x)
-  hidden_out = pd.matmul(U, h.pre(n=1))
-  sum = pd.add_two(fc_out, hidden_out)
-  act = pd.sigmoid(sum)
-  h.update(act)                       # update memory with act
-  net.set_outputs(0, act, hidden_out) # two outputs
-
+x = sequence([10, 20, 30]) # shape=[None, 1]
+m = var(0) # shape=[1]
+W = var(0.314, param=true) # shape=[1]
+U = var(0.375, param=true) # shape=[1]
+
+rnn = pd.rnn()
+with rnn.step():
+  h = rnn.memory(init = m)
+  h_prev = rnn.previous_memory(h)
+  a = layer.fc(W, x)
+  b = layer.fc(U, h_prev)  
+  s = pd.add(a, b)
+  act = pd.sigmoid(s)
+  rnn.update_memory(h, act)
+  rnn.output(a, b)
 o1, o2 = rnn()
-print o1, o2
 ```
-
 has its equivalent C++ program as follows
 
 ```c++
 int* x = {10, 20, 30};
-int m = 0;
-int W = some_value();
-int U = some_other_value();
+int* m = {0};
+int* W = {0.314};
+int* U = {0.375};
 
 int mem[sizeof(x) / sizeof(x[0]) + 1];
 int o1[sizeof(x) / sizeof(x[0]) + 1];
@@ -131,25 +135,21 @@ int o2[sizeof(x) / sizeof(x[0]) + 1];
 for (int i = 1; i <= sizeof(x)/sizeof(x[0]); ++i) {
   int x = x[i-1];
   if (i == 1) mem[0] = m;
-  int fc_out = W * x;
-  int hidden_out = Y * mem[i-1];
-  int sum = fc_out + hidden_out;
+  int a = W * x;
+  int b = Y * mem[i-1];
+  int s = fc_out + hidden_out;
   int act = sigmoid(sum);
   mem[i] = act;
   o1[i] = act;
   o2[i] = hidden_out;
 }
-
-print_array(o1);
-print_array(o2);
 ```
 
-
 ## Compilation and Execution
 
-Like TensorFlow programs, a PaddlePaddle program is written in Python.  The first part describes a neural network as a protobuf message, and the rest part executes the message for training or inference.
+Like TensorFlow, a PaddlePaddle program is written in Python. The first part describes a neural network as a protobuf message, and the rest executes the message for training or inference.
 
-The generation of this protobuf message is like what a compiler generates a binary executable file.  The execution of the message that the OS executes the binary file.
+The generation of this protobuf message is similar to how a compiler generates a binary executable file. The execution of the message is similar to how the OS executes the binary file.
 
 ## The "Binary Executable File Format"
 
@@ -186,8 +186,8 @@ Also, the RNN operator in above example is serialized into a protobuf message of
 
 ```
 OpDesc {
-  inputs = {0} // the index of x
-  outputs = {5, 3} // indices of act and hidden_out
+  inputs = {0} // the index of x in vars of BlockDesc above
+  outputs = {5, 3} // indices of act and hidden_out in vars of BlockDesc above
   attrs {
     "memories" : {1} // the index of h
     "step_net" : <above step net>
@@ -203,32 +203,32 @@ This `OpDesc` value is in the `ops` field of the `BlockDesc` value representing
 During the generation of the Protobuf message, the Block should store VarDesc (the Protobuf message which describes Variable) and OpDesc (the Protobuf message which describes Operator).
 
 VarDesc in a block should have its name scope to avoid local variables affect parent block's name scope.
-Child block's name scopes should inherit the parent's so that OpDesc in child block can reference a VarDesc that stored in parent block. For example
+Child block's name scopes should inherit the parent's so that OpDesc in child block can reference a VarDesc that stored in parent block. For example:
 
 ```python
-a = pd.Varaible(shape=[20, 20])
+a = pd.Variable(shape=[20, 20])
 b = pd.fc(a, params=["fc.w", "fc.b"])
 
 rnn = pd.create_rnn()
-with rnn.stepnet() as net:
-    x = net.set_inputs(a)
+with rnn.stepnet():
+    x = a.as_step_input()
     # reuse fc's parameter
     fc_without_b = pd.get_variable("fc.w")
-    net.set_outputs(fc_without_b)
+    rnn.output(fc_without_b)
 
 out = rnn()
 ```
-the method `pd.get_variable` can help retrieve a Variable by a name, a Variable may store in a parent block, but might be retrieved in a child block, so block should have a variable scope that supports inheritance.
+The method `pd.get_variable` can help retrieve a Variable by the name. The Variable may be stored in a parent block, but might be retrieved in a child block, so block should have a variable scope that supports inheritance.
 
 In compiler design, the symbol table is a data structure created and maintained by compilers to store information about the occurrence of various entities such as variable names, function names, classes, etc.
 
 To store the definition of variables and operators, we define a C++ class `SymbolTable`, like the one used in compilers.
 
-`SymbolTable` can do the following stuff:
+`SymbolTable` can do the following:
 
 - store the definitions (some names and attributes) of variables and operators,
-- to verify if a variable was declared,
-- to make it possible to implement type checking (offer Protobuf message pointers to `InferShape` handlers).
+- verify if a variable was declared,
+- make it possible to implement type checking (offer Protobuf message pointers to `InferShape` handlers).
 
 
 ```c++
@@ -240,19 +240,18 @@ class SymbolTable {
 
   OpDesc* NewOp(const string& name="");
 
-  // TODO determine whether name is generated by python or C++
-  // currently assume that a unique name will be generated by C++ if the
-  // argument name left default.
-  VarDesc* NewVar(const string& name="");
+  // TODO determine whether name is generated by python or C++.
+  // Currently assume that a unique name will be generated by C++ if the
+  // argument name is left default.
+  VarDesc* Var(const string& name="");
 
-  // find a VarDesc by name, if recursive true, find parent's SymbolTable
+  // find a VarDesc by name, if recursive is true, find parent's SymbolTable
   // recursively.
   // this interface is introduced to support InferShape, find protobuf messages
   // of variables and operators, pass pointers into InferShape.
-  // operator
   //
   // NOTE maybe some C++ classes such as VarDescBuilder and OpDescBuilder should
-  // be proposed and embedded into pybind to enable python operate on C++ pointers.
+  // be proposed and embedded into pybind to enable python operation on C++ pointers.
   VarDesc* FindVar(const string& name, bool recursive=true);
 
   OpDesc* FindOp(const string& name);
@@ -270,7 +269,7 @@ class SymbolTable {
 After all the description of variables and operators is added into SymbolTable,
 the block has enough information to run.
 
-The `Block` class takes a `BlockDesc` as input, and provide `Run` and `InferShape` functions.
+The `Block` class takes a `BlockDesc` as input, and provides `Run` and `InferShape` functions.
 
 
 ```c++
@@ -302,7 +301,7 @@ public:
   void CreateVariables(const framework::Scope& scope);
   void CreateOperators();
 
-  // some other necessary interfaces of NetOp are list below
+  // some other necessary interfaces of NetOp are listed below
   // ...
 
 private:
@@ -316,15 +315,14 @@ private:
 Block inherits from OperatorBase, which has a Run method.
 Block's Run method will run its operators sequentially.
 
-There is another important interface called `Eval`, which take some arguments called targets, and generate a minimal graph which takes targets as the end points and creates a new Block,
-after `Run`, `Eval` will get the latest value and return the targets.
+There is another important interface called `Eval`, which takes some arguments called targets and generates a minimal graph which treats targets as the end points and creates a new Block. After `Run`, `Eval` will get the latest value and return the targets.
 
 The definition of Eval is as follows:
 
 ```c++
 // clean a block description by targets using the corresponding dependency graph.
 // return a new BlockDesc with minimal number of operators.
-// NOTE not return a Block but the block's description so that this can be distributed
+// NOTE: The return type is not a Block but the block's description so that this can be distributed
 // to a cluster.
 BlockDesc Prune(const BlockDesc& desc, vector<string> targets);
 

doc/design/executor.md

+# Executor Design Doc
+
+## Motivation
+
+We use executor to do the runtime evaluation of a `ProgramDesc`.
+
+## Overview
+
+An executor takes a `ProgramDesc`, a `block_id` and a `Scope`.  The `ProgramDesc` is a list of blocks and each block contains the protobuf definition of all the parameters and operators. The `block_id` specifies the entrance block. And the `Scope` is the container of all the variable instance, which is persistent throughout different runs.
+
+### What does executor do?
+
+It evaluates all the operators in the `block_id`th block of a `ProgramDesc`.
+
+### What does executor NOT do?
+
+It does not do runtime optimization, meaning intelligently parse the dependency of each op a choose which one to be run and in which order they should be run.
+
+It does not do graph partitioning, meaning dividing the `ProgramDesc` into several small pieces and executing them on different devices.
+
+## Implementation
+
+`Executor` evaluates a `ProgramDesc`. Essentially, it instantiates Variables and Operators, then run all the operators in sequence. [[code]](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/executor.cc)

doc/design/gan_api.md

+# Design for GAN
+
+GAN (General Adversarial Net [https://arxiv.org/abs/1406.2661]) is an important model for unsupervised learning and widely used in many areas. 
+
+It applies several important concepts in machine learning system design, including building and running subgraphs, dependency tracing, different optimizers in one executor and so forth.
+
+In our GAN design, we wrap it as a user-friendly easily customized python API to design different models. We take the conditional DC-GAN (Unsupervised Representation Learning with Deep Convolutional Generative Adversarial Networks [https://arxiv.org/abs/1511.06434]) as an example due to its good performance on image generation.
+
+<p align="center">
+<img src="./test.dot.png" width = "35%" align="center"/><br/>
+Figure 1. The overall running logic of GAN. The black solid arrows indicate the forward pass; the green dashed arrows indicate the backward pass of generator training; the red dashed arrows indicate the backward pass of the discriminator training. The BP pass of the green (red) arrow should only update the parameters in the green (red) boxes. The diamonds indicate the data providers. d\_loss and g\_loss marked in red and green are the two targets we would like to run.
+</p>
+
+The operators, layers and functions required/optional to build a GAN demo is summarized in https://github.com/PaddlePaddle/Paddle/issues/4563.
+
+<p align="center">
+<img src="./dcgan.png" width = "90%" align="center"/><br/>
+Figure 2. Photo borrowed from the original DC-GAN paper.
+</p>
+
+## The Conditional-GAN might be a class. 
+This design we adopt the popular open source design in https://github.com/carpedm20/DCGAN-tensorflow and https://github.com/rajathkmp/DCGAN. It contains following data structure:
+
+- DCGAN(object): which contains everything required to build a GAN model. It provides following member functions methods as API:
+
+- __init__(...): Initialize hyper-parameters (like conv dimension and so forth), and declare model parameters of discriminator and generator as well.
+
+- generator(z, y=None): Generate a fake image from input noise z. If the label y is provided, the conditional GAN model will be chosen.
+Returns a generated image.
+
+- discriminator(image):
+Given an image, decide if it is from a real source or a fake one. 
+Returns a 0/1 binary label.
+
+- build_model(self):
+build the whole GAN model, define training loss for both generator and discrimator.
+
+## Discussion on Engine Functions required to build GAN
+- Trace the tensor and variable dependency in the engine executor. (Very critical, otherwise GAN can'be be trained correctly)
+- Different optimizers responsible for optimizing different loss.
+
+To be more detailed, we introduce our design of DCGAN as following:
+
+### Class member Function: Initializer
+- Set up hyper-parameters, including condtional dimension, noise dimension, batch size and so forth.
+- Declare and define all the model variables. All the discriminator parameters are included in the list self.theta_D and all the generator parameters are included in the list self.theta_G.
+```python
+class DCGAN(object):
+  def __init__(self, y_dim=None):
+  
+    # hyper parameters  
+    self.y_dim = y_dim # conditional gan or not
+    self.batch_size = 100
+    self.z_dim = z_dim # input noise dimension
+
+    # define parameters of discriminators
+    self.D_W0 = pd.Variable(shape=[3,3, 1, 128], data=pd.gaussian_normal_randomizer())
+    self.D_b0 = pd.Variable(np.zeros(128)) # variable also support initialization using a  numpy data
+    self.D_W1 = pd.Variable(shape=[784, 128], data=pd.gaussian_normal_randomizer())
+    self.D_b1 = pd.Variable(np.zeros(128)) # variable also support initialization using a  numpy data
+    self.D_W2 = pd.Varialble(np.random.rand(128, 1))
+    self.D_b2 = pd.Variable(np.zeros(128))
+    self.theta_D = [self.D_W0, self.D_b0, self.D_W1, self.D_b1, self.D_W2, self.D_b2]
+
+    # define parameters of generators
+    self.G_W0 = pd.Variable(shape=[784, 128], data=pd.gaussian_normal_randomizer())
+    self.G_b0 = pd.Variable(np.zeros(128)) # variable also support initialization using a  numpy data
+    self.G_W1 = pd.Variable(shape=[784, 128], data=pd.gaussian_normal_randomizer())
+    self.G_b1 = pd.Variable(np.zeros(128)) # variable also support initialization using a  numpy data
+    self.G_W2 = pd.Varialble(np.random.rand(128, 1))
+    self.G_b2 = pd.Variable(np.zeros(128))
+    self.theta_G = [self.G_W0, self.G_b0, self.G_W1, self.G_b1, self.G_W2, self.G_b2]
+```
+
+### Class member Function: Generator
+- Given a noisy input z, returns a fake image.
+- Concatenation, batch-norm, FC operations required;
+- Deconv layer required, which is missing now...
+```python
+class DCGAN(object):
+  def generator(self, z, y = None):
+    # input z: the random noise
+    # input y: input data label (optional)
+    # output G_im: generated fake images
+    
+    if not self.y_dim:
+      z = pd.layer.concat(1, [z, y])
+      
+    G_h0 = pd.layer.fc(z, self.G_w0, self.G_b0)
+    G_h0_bn = pd.layer.batch_norm(G_h0)
+    G_h0_relu = pd.layer.relu(G_h0_bn)
+    
+    G_h1 = pd.layer.deconv(G_h0_relu, self.G_w1, self.G_b1)
+    G_h1_bn = pd.layer.batch_norm(G_h1)
+    G_h1_relu = pd.layer.relu(G_h1_bn)
+    
+    G_h2 = pd.layer.deconv(G_h1_relu, self.G_W2, self.G_b2))
+    G_im = pd.layer.tanh(G_im)
+    return G_im
+```
+
+### Class member function: Discriminator
+- Given a noisy input z, returns a fake image.
+- Concatenation, Convolution, batch-norm, FC, Leaky-ReLU operations required;
+```python
+class DCGAN(object):
+  def discriminator(self, image):
+    # input image: either generated images or real ones
+    # output D_h2: binary logit of the label
+
+    D_h0 = pd.layer.conv2d(image, w=self.D_w0, b=self.D_b0)
+    D_h0_bn = pd.layer.batchnorm(h0)
+    D_h0_relu = pd.layer.lrelu(h0_bn)
+    
+    D_h1 = pd.layer.conv2d(D_h0_relu, w=self.D_w1, b=self.D_b1)
+    D_h1_bn = pd.layer.batchnorm(D_h1)
+    D_h1_relu = pd.layer.lrelu(D_h1_bn)
+    
+    D_h2 = pd.layer.fc(D_h1_relu, w=self.D_w2, b=self.D_b2)
+    return D_h2
+```
+
+### Class member function: Build the model
+- Define data readers as placeholders to hold the data;
+- Build generator and discriminators;
+- Define two training losses for discriminator and generator, respectively. 
+If we have execution dependency engine to back-trace all tensors, the module building our GAN model will be like this:
+```python
+class DCGAN(object):
+  def build_model(self):
+    if self.y_dim:
+        self.y = pd.data(pd.float32, [self.batch_size, self.y_dim])
+    self.images = pd.data(pd.float32, [self.batch_size, self.im_size, self.im_size])
+    self.faked_images = pd.data(pd.float32, [self.batch_size, self.im_size, self.im_size])
+    self.z = pd.data(tf.float32, [None, self.z_size])
+    
+    # step 1: generate images by generator, classify real/fake images with discriminator
+    if self.y_dim: # if conditional GAN, includes label
+        self.G = self.generator(self.z, self.y)
+        self.D_t = self.discriminator(self.images)
+        # generated fake images
+        self.sampled = self.sampler(self.z, self.y)
+        self.D_f = self.discriminator(self.G)
+    else: # original version of GAN
+        self.G = self.generator(self.z)
+        self.D_t = self.discriminator(self.images)
+        # generate fake images
+        self.sampled = self.sampler(self.z)
+        self.D_f = self.discriminator(self.images)
+    
+    # step 2: define the two losses
+    self.d_loss_real = pd.reduce_mean(pd.cross_entropy(self.D_t, np.ones(self.batch_size))
+    self.d_loss_fake = pd.reduce_mean(pd.cross_entropy(self.D_f, np.zeros(self.batch_size))
+    self.d_loss = self.d_loss_real + self.d_loss_fake
+    
+    self.g_loss = pd.reduce_mean(pd.cross_entropy(self.D_f, np.ones(self.batch_szie))
+```
+
+If we do not have dependency engine but blocks, the module building our GAN model will be like this:
+```python
+class DCGAN(object):
+  def build_model(self, default_block):
+    # input data in the default block
+    if self.y_dim:
+        self.y = pd.data(pd.float32, [self.batch_size, self.y_dim])
+    self.images = pd.data(pd.float32, [self.batch_size, self.im_size, self.im_size])
+    # self.faked_images = pd.data(pd.float32, [self.batch_size, self.im_size, self.im_size])
+    self.z = pd.data(tf.float32, [None, self.z_size])
+
+    # step 1: generate images by generator, classify real/fake images with discriminator
+    with pd.default_block().g_block():
+      if self.y_dim: # if conditional GAN, includes label
+        self.G = self.generator(self.z, self.y)
+        self.D_g = self.discriminator(self.G, self.y)
+      else: # original version of GAN
+        self.G = self.generator(self.z)
+        self.D_g = self.discriminator(self.G, self.y)
+      self.g_loss = pd.reduce_mean(pd.cross_entropy(self.D_g, np.ones(self.batch_szie))
+    
+    with pd.default_block().d_block():
+      if self.y_dim: # if conditional GAN, includes label
+        self.D_t = self.discriminator(self.images, self.y)
+        self.D_f = self.discriminator(self.G, self.y)
+      else: # original version of GAN
+        self.D_t = self.discriminator(self.images)
+        self.D_f = self.discriminator(self.G)
+
+      # step 2: define the two losses
+      self.d_loss_real = pd.reduce_mean(pd.cross_entropy(self.D_t, np.ones(self.batch_size))
+      self.d_loss_fake = pd.reduce_mean(pd.cross_entropy(self.D_f, np.zeros(self.batch_size))
+      self.d_loss = self.d_loss_real + self.d_loss_fake
+```
+Some small confusion and problems with this design:
+- D\_g and D\_f are actually the same thing, but has to be written twice; i.e., if we want to run two sub-graphs conceptually, the same codes have to be written twice if they are shared by the graph.
+- Requires ability to create a block anytime, rather than in if-else or rnn only;
+
+## Main function for the demo:
+Generally, the user of GAN just need to the following things:
+- Define an object as DCGAN class;
+- Build the DCGAN model;
+- Specify two optimizers for two different losses with respect to different parameters.
+```python
+# pd for short, should be more concise.
+from paddle.v2 as pd
+import numpy as np
+import logging
+
+if __name__ == "__main__":
+    # dcgan class in the default graph/block
+    # if we use dependency engine as tensorflow
+    # the codes, will be slightly different like:
+    # dcgan = DCGAN()
+    # dcgan.build_model()
+    with pd.block() as def_block:
+      dcgan = DCGAN()
+      dcgan.build_model(def_block)
+
+    # load mnist data
+    data_X, data_y = self.load_mnist()
+    
+    # Two subgraphs required!!!
+    with pd.block().d_block():
+      d_optim = pd.train.Adam(lr = .001, beta= .1)
+      d_step = d_optim.minimize(dcgan.d_loss, dcgan.theta_D)
+    with pd.block.g_block():
+      g_optim = pd.train.Adam(lr = .001, beta= .1)
+      g_step = pd.minimize(dcgan.g_loss, dcgan.theta_G)
+
+    # executor
+    sess = pd.executor()
+    
+    # training
+    for epoch in xrange(10000):
+      for batch_id in range(N / batch_size):
+        idx = ...
+        # sample a batch
+        batch_im, batch_label = data_X[idx:idx+batch_size], data_y[idx:idx+batch_size]
+        # sample z
+        batch_z = np.random.uniform(-1., 1., [batch_size, z_dim])
+
+        if batch_id % 2 == 0:
+          sess.run(d_step, 
+                   feed_dict = {dcgan.images: batch_im,
+                                dcgan.y: batch_label,
+                                dcgan.z: batch_z})
+        else:
+          sess.run(g_step,
+                   feed_dict = {dcgan.z: batch_z})
+```
+
+# More thinking about dependency engine v.s. block design:
+- What if we just want to run an intermediate result? Do we need to run the whole block/graph?
+- Should we call eval() to get the fake images in the first stage? And then train the discriminator in the second stage?

doc/design/if_else_op.md

-IfOp should have only one branch. An IfOp operator takes a `cond` variable whose value must be a vector of N boolean elements. Its return value has N instances. If cond[i] == True, input instance input[i] will go through true_block() and generate output[i]; otherwise it will produce output from false_bloack().
+# The `IfElse` Operator
 
-```python
-import paddle as pd
+PaddlePaddle's `IfElse` operator differs from TensorFlow's:
 
-x = var()
-y = var()
-cond = var()
-default_value = var()
-b = pd.create_ifelseop(inputs=[x], output_num=1)
-with b.true_block():
-    x = b.inputs(0)
-    z = operator.add(x, y)
-    b.set_output(0, operator.softmax(z))
-
-with b.false_block():
-    x = b.inputs(0)
-    z = layer.fc(x)
-    b.set_output(0, operator.softmax(z))
-
-out = b(cond)
-```
+- the TensorFlow version takes a scalar boolean value as the condition so that the whole mini-batch goes to either the true or the false branch, whereas
+- the PaddlePaddle version takes a vector of boolean value as the condition, and instances corresponding to true values go to the true branch, those corresponding to false values go to the false branch.
+
+## Example
+
+The following PaddlePaddle program shows the usage of the IfElse operator:
 
-If only true_block is set in an IfElseOp, a special case is that we can have a default value for false as:
 ```python
 import paddle as pd
 
-x = var()
-y = var()
-cond = var()
-default_value = var()
-b = pd.create_ifelseop(inputs=[x], output_num=1, default_value)
-
-with b.true_block():
-    x = b.inputs(0)
-    z = operator.add(x, y)
-    b.set_output(0, operator.softmax(z))
+x = minibatch([10, 20, 30]) # shape=[None, 1]
+y = var(1) # shape=[1], value=1
+z = minibatch([10, 20, 30]) # shape=[None, 1]
+cond = larger_than(x, 15) # [false, true, true]
+
+ie = pd.ifelse()
+with ie.true_block():
+    d = pd.layer.add(x, y)
+    ie.output(d, pd.layer.softmax(d))
+with ie.false_block():
+    d = pd.layer.fc(z)
+    ie.output(d, d+1)
+o1, o2 = ie(cond)
+```
 
-out = b(cond)
+A challenge to implement the `IfElse` operator is to infer those variables to be split, or, say, to identify the variable of the mini-batch or those derived from the mini-batch.
+
+An equivalent C++ program is as follows:
+
+```c++
+namespace pd = paddle;
+
+int x = 10;
+int y = 1;
+int z = 10;
+bool cond = false;
+int o1, o2;
+if (cond) {
+  int d = x + y;
+  o1 = z;
+  o2 = pd::layer::softmax(z);
+} else {
+  int d = pd::layer::fc(z);
+  o1 = d;
+  o2 = d+1;
+}
 ```
-where default_value is a list of vars for `cond` == False.

doc/design/images/graph_construction_example.dot

@@ -33,7 +33,6 @@ digraph ImageClassificationGraph {
 
         cost -> MSE_Grad [color=red];
         d_cost -> MSE_Grad [color=red];
-        x -> MSE_Grad [color=red];
         l -> MSE_Grad [color=red];
         y -> MSE_Grad -> d_y [color=red];
 

doc/design/infer_var_type.md

+# Design Doc: InferVarType
+
+## The Problem Posed
+
+The variable in our design can hold variant types. Such as `LoDTensor` and `SelectedRows`. An operator should be able to inference the variable types of its output.
+
+For example, a `lookup table` operator takes two `LoDTensor`; one is a float tensor as the embedding table, the other is an int tensor as word ID. The gradient operator of `lookup table` will generate a `SelectedRows` as its output. A `sum` operator can take both `LoDTensor` and `SelectedRows` as its inputs and will generate a `LoDTensor` if any of its inputs is `LoDTensor`, otherwise, the `sum` operator will generate `SelectedRows` as its output.
+
+The variable type will be constant at runtime. Every variable's type can either be set by the user (input data and parameter) or be inferred by the operator in compile time.
+
+## Proposed Solution
+
+The `InferVarType` is a compile-time function which is registered to each operator. The inferface of that function is:
+
+
+```c++
+using InferVarTypeFN = std::function<
+    void (const OpDescBind& /*op_desc*/, BlockDescBind* /*block*/)>;
+```
+
+It takes an operator description as its input and will write the output variable type and store them in block description.
+
+The `InferVarTypeFN` will be registered in `OpInfo`, to replace `infer_var_type_` field. The `OpInfo` should be
+
+```cpp
+struct OpInfo {
+  InferVarTypeFN infer_var_type_;
+  ...
+};
+```
+
+The default `InferVarType` will set output type as `LoDTensor`. It can be done by `GetInferVarType()`.
+
+```cpp
+void DefaultInferVarType(const OpDescBind& op_desc, BlockDescBind* block) {
+  // set the output type of variable as `LoDTensor`.
+  // ...
+}
+
+struct OpInfo {
+  InferVarTypeFN infer_var_type_;
+  InferVarTypeFN GetInferVarType() const {
+    if (infer_var_type_) {
+      return infer_var_type_;
+    } else {
+      return DefaultInferVarType;
+    }
+  }
+};
+```
+
+## Register InferVarType
+
+We provide a thin base class for registering an `InferVarTypeFN`. To use a base class will ease the implementation of registry since we can detect the registry entry is an `InferVarTypeFN` or not.
+
+```cpp
+class VarTypeInferer {
+public:
+  virtual void operator()(const OpDescBind& op_desc, BlockDescBind* block) const = 0;
+}
+```
+
+Operator developers can write the specialize `VarTypeInferer` as follow.
+
+```cpp
+class SpecialVarTypeInferer : public VarTypeInferer {
+public:
+  virtual void operator()(const OpDescBind& op_desc, BlockDescBind* block) const {
+    // .. own logic
+  }
+}
+```
+
+Then user can register the `InferVarType` just like `GradOpDescMaker` and `OpInfoMaker`.
+
+```
+REGISTER_OPERATOR(some_op, OpType, SpecialVarTypeInferer, ...);
+```

doc/design/optimizer.md

+## Optimizer Design
+
+### The Problem
+
+A PaddlePaddle program, or a block, is a sequence of operators operating variables.  A training program needs to do three kinds of works:
+
+1. the forward pass, which computes intermediate results and the cost(s),
+1. the backward pass, which derives gradients from intermediate results and costs, and
+1. the optimization pass, which update model parameters to optimize the cost(s).
+
+These works rely on three kinds of operators:
+
+1. forward operators,
+1. gradient operators, and
+1. optimization operators.
+
+It's true that users should be able to create all these operators manually by calling some low-level API, but it would be much more convenient if they could only describe the forward pass and let PaddlePaddle create the backward and optimization operators automatically.
+
+In this design, we propose a high-level API that automatically derives the optimisation pass and operators from the forward pass.
+
+
+### High-level Python API to describe the training process
+
+1. User write code to describe the network:
+
+	```python
+	images = layer.data("images")
+	labels = layer.data("labels")
+	w1 = pd.var("w1")
+	b1 = pd.var("b1")
+	hidden = layer.fc(images, w=w1, b=b1)
+	cost = layer.mse(hidden, labels)
+	```
+
+	The above code snippet will create forward operators in [Block](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/block.md).
+
+
+2. Users create a certain kind of Optimizer with some argument.
+
+	```python
+	optimizer = AdagradOptimizer(learing_rate=0.001)
+	```
+
+3. Users use the optimizer to `minimize` a certain `cost` through updating parameters in parameter_list.
+
+	```python
+	opt_op_list = optimizer.minimize(cost, parameter_list=[w1, b1])
+	```
+	The above code snippet will create gradient and optimization operators in Block. The return value of `minimize()` is list of optimization operators that will be run by session.
+
+4. Users use Session/Executor to run this opt_op_list as target to do training.
+
+	```python
+	sess.run(target= opt_op_list, ...)
+	```
+
+#### Optimizer Python interface:
+
+```python
+class Optimizer(object):
+    """Optimizer Base class.
+
+    """
+
+    def __init__(self):
+        pass
+
+    def create_backward_pass(self, loss, parameter_list=None):
+        """
+        create and add gradient Operators in BlockDesc to Compute gradients of `loss`
+        for parameters in parameter_list
+
+        Args:
+          loss: an variable generated by cost function.
+          parameter_list: parameters that need to compute gradient and update to optimize the lost.
+
+        Returns:
+          list of (parameters, gradients) pair.
+        """
+        return None
+
+    def create_optimization_pass(self, parameters_and_grads):
+        """Add optimization operators to update gradients to variables.
+
+        Args:
+          parameters_and_grads: a list of (variable, gradient) pair to update.
+
+        Returns:
+          optmization_op_list: a list of optimization operator that will update parameter using gradient.
+        """
+        return None
+
+    def minimize(self, loss, parameter_list):
+        """Add operations to minimize `loss` by updating `parameter_list`.
+
+        This method combines interface `create_backward_pass()` and
+        `create_optimization_pass()` into one.
+        """
+        params_grads = self.create_backward_pass(loss, parameter_list)
+        update_ops = self.create_optimization_pass(params_grads)
+        return update_ops
+
+```
+
+Users can inherit the Optimizer above to create their own Optimizer with some special logic, such as AdagradOptimizer.

doc/design/program.md

-# Design Doc: ProgramDesc
+# Design Doc: PaddlePaddle Programs
 
-The basic structure of a PaddlePaddle program is some nested blocks, as a C++ or Java program.
+## Compile and Execution
+
+A PaddlePaddle program consists of two parts -- the first generates a `ProgramDesc` protobuf message that describes the program, and the second runs this message using a C++ class `Executor`.
 
-As described in [graph.md](./graph.md), the first five lines of the following PaddlePaddle program
+A simple example PaddlePaddle program can be found in [graph.md](./graph.md):
 
 ```python
 x = layer.data("images")
@@ -13,36 +15,112 @@ optimize(cost)
 train(cost, reader=mnist.train())
 ```
 
-generates, or compiles, a PaddelPaddle program, which is represented by the following protobuf message:
+The first five lines of the following PaddlePaddle program generates, or, compiles, the `ProgramDesc` message.  The last line runs it.
 
-```protobuf
-message ProgramDesc {
-  repeated BlockDesc blocks = 1;
+## Programs and Blocks
+
+The basic structure of a PaddlePaddle program is some nested blocks, as a C++ or Java program.
+
+- program: some nested blocks
+- [block](./block.md):
+  - some local variable definitions, and
+  - a sequence of operators
+
+The concept of block comes from usual programs.  For example, the following C++ program has three blocks:
+
+```c++
+int main() { // block 0
+  int i = 0;
+  if (i < 10) { // block 1
+    for (int j = 0; j < 10; j++) { // block 2
+    }
+  }
+  return 0;
 }
+```
+
+The following PaddlePaddle program has three blocks:
+
+```python
+import paddle as pd  // block 0
+
+x = minibatch([10, 20, 30]) # shape=[None, 1]
+y = var(1) # shape=[1], value=1
+z = minibatch([10, 20, 30]) # shape=[None, 1]
+cond = larger_than(x, 15) # [false, true, true]
 
+ie = pd.ifelse()
+with ie.true_block():  // block 1
+    d = pd.layer.add_scalar(x, y)
+    ie.output(d, pd.layer.softmax(d))
+with ie.false_block():  // block 2
+    d = pd.layer.fc(z)
+    ie.output(d, d+1)
+o1, o2 = ie(cond)
+```
+
+## `BlockDesc` and `ProgramDesc`
+
+All protobuf messages are defined in `framework.proto`.
+
+`BlockDesc` is straight-forward -- it includes local variable definitions, `vars`, and a sequence of operators, `ops`.
+
+```protobuf
 message BlockDesc {
   required int32 parent = 1;
   repeated VarDesc vars = 2;
   repeated OpDesc ops = 3;
 }
+```
+
+The parent ID indicates the parent block so that operators in a block can refer to variables defined locally and also those defined in their ancestor blocks.
+
+All hierarchical blocks in a program are flattened and stored in an array. The block ID is the index of the block in this array.
+
+```protobuf
+message ProgramDesc {
+  repeated BlockDesc blocks = 1;
+}
+```
+
+
+### Global Block
 
+The global block is the first one in the above array.
+
+## Operators that Use Blocks
+
+In the above example, the operator `IfElseOp` has two blocks -- the true branch and the false branch.
+
+The definition of `OpDesc` shows that an operator could have some attributes:
+
+```protobuf
 message OpDesc {
   AttrDesc attrs = 1;
   ...
 }
+```
 
+and an attribute could be of type block, which is, in fact, a block ID as described above:
+
+```
 message AttrDesc {
-  required AttrType type = 1;
+  required string name = 1;
 
-  // index into ProgramDesc::blocks when type==BLOCK
-  optional int32 block = 2;
+  enum AttrType {
+    INT = 1,
+    STRING = 2,
+    ...
+    BLOCK = ...
+  }
+  required AttrType type = 2;
+
+  optional int32 block = 10; // when type == BLOCK
   ...
 }
 ```
 
-When each of the first five lines runs, related Python function, e.g., `layer.fc`, calls C++ InferShape functions.  This InferShape function needs to access the properties of VarDesc's accessed by the current OpDesc. These VarDesc's might not be defined in the current block, but in some ancestor blocks.  This requires that we can trace the parent of a block.
-
-A nested block is often an attribute of an operator, most likely, an IfElseOp or a WhileOp.  In above solution, all blocks are in `ProgramDesc::blocks`, this implicitly assigns a zero-based ID to each block -- the index of the block in `ProgramDesc::blocks`.  So that `AttrDesc::block` could be an integer block ID.
+## InferShape
 
 With this design, the InferShape function should take the following parameters:
 

doc/design/python_api.md

+# Design Doc: Python API
+
+Due to the refactorization of the PaddlePaddle core, we need Python classes to construct corresponding protobuf messages that describe a DL program.
+
+| Python classes | Protobuf messages |
+| --- | --- |
+| Program | ProgramDesc |
+| Block | BlockDesc |
+| Operator | OpDesc |
+| Variable | VarDesc |
+
+Please be aware that these Python classes need to maintain some construction-time information, which are not part of the protobuf messages.
+
+## Core Concepts
+
+### Program
+
+A `ProgramDesc` describes a [DL program](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/program.md), which is composed of an array of `BlockDesc`s.  The `BlockDesc`s in a `ProgramDesc` can have a tree-like hierarchical structure. However, the `ProgramDesc` onlys stores a flattened array of `BlockDesc`s. A `BlockDesc` refers to its parent block by its index in the array.  For example, operators in the step block of an RNN operator need to be able to access variables in its ancestor blocks.
+
+Whenever we create a block, we need to set its parent block to the current block, hence the Python class `Program` needs to maintain a data member `current_block`.
+
+```python
+class Program(objects):
+    def __init__(self):
+        self.desc = core.NewProgram() # a C++ ProgramDesc pointer.
+        self.blocks = vector<Block>()
+        self.blocks.append(Block(self, -1)) # the global block
+        self.current_block = 0          # initialized to the global block
+
+    def global_block():
+        return self.blocks[0]
+
+    def current_block():
+        return self.get_block(self.current_block)
+
+    def rollback():
+        self.current_block = self.current_block().parent_idx
+
+    def create_block():
+        new_block_idx = len(self.block)
+        self.blocks.append(Block(self, self.current_block))
+        self.current_block = new_block_idx
+        return current_block()
+```
+
+`Program` is an accessor to the protobuf message `ProgramDesc`, which is created in C++ space, because the InferShape function is in C++, which manipulates `VarDesc` messages, which are in turn members of `BlockDesc`, which is a member of `ProgramDesc`.
+
+`Program` creates the first block as the global block in its constructor.  All parameters and their initializer operators are in the global block.
+
+### Block
+
+A [Block](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/block.md) includes
+
+1. a map from variable names to an instance of the Python `Variable` class, and
+1. a list of `Operator` instances.
+
+```python
+class Block(objects):
+    def __init__(self, program, parent_idx):
+        self.desc = core.NewBlock(program.desc)
+        self.program = program
+        self.vars = map<string, Variable>()
+        self.ops = vector<Operator>()
+        self.parent_idx = parent_idx
+
+    def create_var(self, ...):
+        return Variable(self, ...)
+
+    def _create_global_var(self, ...):
+        program.global_block().create_var(...)
+
+    def create_parameter(self, name, ...):
+        # Parameter is a subclass of variable. See Parameter section for details.
+        self.vars[name] = Parameter(self._create_global_var(...), ...)
+        return self.vars[name]
+
+    def append_operator(self, ...):
+        self.ops.append(Operator(self, ...))
+
+    def prepend_operator(self, ...): # Parameter's ctor prepands initialize operators.
+       self.ops.prepend(Operator(self, ...))
+```
+
+`create_parameter` is necessary because parameters are global variables, defined in the global block, but can be created in some sub-blocks. For example, an FC layer in the step block of an RNN operator.
+
+`prepend_operator` is necessary because the constructor of `Parameter` needs to create the initialize (or load) operator of the parameter, and would like to put it in the *preamble* of the global block.
+
+### Operator
+
+The `Operator` class fills in the `OpDesc` message and calls the C++ function `InferShape` to infer the output shapes from the input shapes.
+
+```python
+class Operator(object):
+    def __init__(self,
+                 block,  # Block
+                 type,   # string
+                 inputs, # dict<string, Variable>
+                 outputs,# dict<stirng, Variable>
+                 attrs   # dict<string, Any>
+                 ):
+        self.desc = core.NewOpDesc(block.desc, type, inputs, outputs, attrs)
+        core.infer_shape(self.desc, inputs, outputs)
+
+    def type(self):
+        return self.desc.type()
+```
+
+`Operator` creates the `OpDesc` message in C++ space, so that it can call the `InferShape` function, which is in C++.
+
+### Variable
+
+Operators take Variables as its inputs and outputs.
+
+```python
+class Variable(object):
+    def __init__(self,
+                 block=None,      # Block
+                 name=None,       # string
+                 shape,           # tuple
+                 dtype="float32", # string
+                 lod_level=None   # int
+                 ):
+        if name is None:
+            name = unique_name_generator()
+        self.name = name
+        self.block = block
+        self.desc = core.NewVarDesc(block.desc, name, shape, lod_level)
+        self.writer = None
+```
+
+Please be aware of `self.writer`, that tracks operator who creates the variable.  It possible that there are more than one operators who write a variable, but in Python space, each write to a variable is represented by a Variable class.  This is guaranteed by the fact that **`core.NewVarDesc` must NOT create a new `VarDesc` message if its name already exists in the specified block**.
+
+### Parameter
+
+A parameter is a global variable with an initializer (or load) operator.
+
+```python
+class Parameter(Variable):
+    def __init__(self,
+                 block=None,      # Block
+                 name=None,       # string
+                 shape,           # tuple
+                 dtype="float32", # string
+                 lod_level=None   # int
+                 trainable,       # bool
+                 initialize_op_attrs,
+                 optimize_op_attrs):
+        super(Parameter, self).__init__(block, name, shape, dtype, lod_level)
+        self.trainable = trainable
+        self.optimize_op_attrs = optimize_op_attrs
+        block.prepend(Operator(block,  # Block
+                               initialize_op_attrs['type'],   # string
+                               None,   # no inputs
+                               self,   # output is the parameter
+                               initialize_op_attrs)
+```
+
+When users create a parameter, they can call
+
+```python
+program.create_parameter(
+  ...,
+  init_attr={
+    type: "uniform_random",
+    min: -1.0,
+    max: 1.0,
+  })
+)
+```
+
+In above example, `init_attr.type` names an initialize operator.  It can also name the load operator
+
+```python
+init_attr={
+ type: "load",
+ filename: "something.numpy",
+}
+```
+
+`optimize_op_attrs` is not in the `VarDesc` message, but kept in the Python instance, as it will be used in the Python space when creating the optimize operator's `OpDesc`, and will be in the `OpDesc` message.
+
+## Layer Function
+
+A layer is a Python function that creates some operators and variables. Layers simplify the work of application programmers.
+
+Layer functions take `Variable` and configuration parameters as its input and return the output variable(s).
+
+For example, `FullyConnected` take one or more variable as its input. The input could be input data or another layer's output. There are many configuration options for a `FullyConnected` layer, such as layer size, activation, parameter names, initialization strategies of parameters, and so on. The `FullyConnected` layer will return an output variable.
+
+
+### Necessity for reusing code between layer functions
+
+There are a lot of code that can be reused. Such as
+
+* Give the default value of configuration. e.g., default initialize strategy for parameters is uniform random with `min = -1.0`, `max = 1.0`. and default initialize strategy for bias is to fill zero.
+* Append the activation operator.
+* Create a temporary variable.
+* Create parameter.
+* Generate a unique name.
+* Add a bias.
+* ...
+
+A mechanism to reuse code between layer functions is necessary. It will be around [150 lines of code](https://github.com/PaddlePaddle/Paddle/pull/4724/files#diff-823b27e07e93914ada859232ae23f846R12) if we write a `FullyConnected` layer without any helper functions.
+
+
+
+### Comparision between global functions and helper class
+
+The `FullyConnected` layer will be as follow when we provide global functions:
+
+```python
+def fc_layer(input, size, param_attr=None, bias_attr=None, act=None, name=None):
+  if name is None:
+    name = unique_name("fc")
+  input = multiple_input(input)
+  param_attr = default_param_attr(param_attr)
+  param_attr = multiple_param_attr(param_attr, len(input))
+
+  # mul
+  mul_results = []
+  for ipt, attr in zip(input, param_attr):
+    shape = ipt.shape[1:] + [size]
+    w = g_program.global_block().create_parameter(shape, ipt.dtype, name, attr)
+    tmp = create_tmp_var(name)
+    g_program.current_block().append_op("mul", {ipt, w}, {tmp})
+  mul_results.append(tmp)
+
+  # add sum
+  ...
+  # add bias
+  ...
+  # add activation
+  ...
+  return out
+```
+
+We can provide many helpers functions for layer developers. However, there are several disadvantages for global helper functions:
+
+1. We need a namespace for these methods, then layer developers can quickly figure out what method they can use.
+2. Global functions will force layer developers to pass its parameter time by time.
+
+So we provide a helper class, `LayerHelper`, to share code between layer functions. The `FullyConnected` Layer will be as follow.
+
+```python
+def fc_layer(input, size, param_attr=None, bias_attr=None, act=None, name=None):
+  helper = LayerHelper(locals())  # pass all parameter to LayerHelper
+
+  mul_results = []
+  for ipt, param in helper.iter_multiple_input_and_param():
+    w = helper.create_parameter(shape=ipt.shape[1:] + [size], dtype = ipt.dtype)
+    tmp = helper.create_tmp_variable()
+    helper.append_op('mul', {ipt, w}, {tmp})
+    mul_results.append(tmp)
+
+  pre_bias = helper.add_sum(mul_results)
+  pre_activation = helper.add_bias(pre_bias)
+  return helper.add_activation(pre_activation)
+```
+
+We not only use the fewer lines of code to write `fc_layer` but also make the code clearer to understand. At the same time, layer developers can figure out what function they can invoke by typing `helper.` in a python editor.
+
+
+### Implementation of layer helper
+
+We just keep all parameters of a layer function as a dictionary in layer helper as a private data member. Every method of layer helper will look up the dictionary after it is invoked. In that way, we can implement a layer helper for all layer functions even some layer does not contain some operator. For example, The `activation` is used by the FullyConnected layer or convolution layers, but a cross-entropy layer does not use it. The example code of `add_activation` are:
+
+```python
+class LayerHelper(object):
+  def __init__(self, **kwargs):  # kwargs is short for `keyword arguments`
+    self.kwargs = kwargs
+
+  def add_activation(self, input_var):
+    act = self.kwargs.get("act", None)  # default value is None
+    if act is None:  # do nothing if no act
+      return input_var
+
+    tmp = self.create_tmp_var(self)
+    self.append_op(type=act, input=input_var, output=tmp)
+    return tmp
+```
+
+## Optimizer
+
+[Optimizer Design Doc](./optimizer.md)

doc/design/refactor/distributed_architecture.md

+# Design Doc: Distributed Training Architecture
+
+## Abstract
+
+PaddlePaddle v0.10.0 uses the "trainer-parameter server"
+architecture. We run multiple replicated instances of trainers (runs
+the same code written by the user) and parameter servers for
+distributed training. This architecture served us well, but has some
+limitations:
+
+1. Need to write special code to handle tasks which should only be run
+  by a single trainer. E.g., initializing model and saving model.
+
+2. Model parallelism is hard: need to write if-else branches conditioned
+  on the trainer ID to partition model onto each trainer, and manually
+  write the inter-model-shard communication code.
+
+3. The user can not directly specify the parameter update rule: need
+   to modify the parameter server C++ code and compile a new
+   binary. This adds complication for researchers: A lot of extra
+   effort is required. Besides, the training job submission program
+   may not allow running arbitrary binaries.
+
+This design doc discusses PaddlePaddle's new distributed training
+architecture that addresses the above limitations.
+
+## Analysis
+
+We will assume the user writes the trainer program by Python, the same
+analysis holds if the trainer program is written in C++.
+
+### Limitation 1
+
+If we look at the Python code that the user writes, there are two
+kinds of functionalities:
+
+- The training logic such as load / save model and print log.
+- The neural network definition such as the definition of the data
+  layer, the fully connected layer, the cost function and the
+  optimizer.
+
+When we training with PaddlePaddle v0.10.0 distributedly, multiple
+replicated Python instances are running on different nodes: both the
+training logic and the neural network computation is replicated.
+
+The tasks that should only run once all belong to the training logic,
+if we only replicate the neural network computation, but do **not**
+replicate the training logic, the limitation could be solved.
+
+### Limitation 2
+
+Model parallelism means running a single model on multiple nodes by
+partitioning the model onto different nodes and managing the
+inter-model-shard communications.
+
+PaddlePaddle should be able to modify the nerual network computation
+definition to support model parallelism automatically. However, the
+computation is only specified in Python code, and PaddlePaddle can not
+modify Python code.
+
+Just like compiler uses a intermediate representation (IR) so that
+programmer does not need to manually optimize their code in most of
+the cases - the compiler will optimize the IR:
+
+<img src="src/compiler.png"/>
+
+We can have our own IR too: PaddlePaddle can support model parallel by
+converting the IR so the user no longer need to manually do it in
+Python:
+
+<img src="src/paddle-compile.png"/>
+
+The IR for PaddlePaddle after refactor is called `Block`, it specifies
+the computation dependency graph and the variables used in the
+computation.
+
+### Limitation 3
+
+The user can not directly specify the parameter update rule for the
+parameter server because the parameter server does not use the same
+computation definition as the trainer. Instead, the update rule is
+baked in the parameter server. The user can not specify the update
+rule in the same way of specifying the trainer computation.
+
+This could be fixed by making the parameter server run the same
+computation definition as the trainer. For a detailed explanation,
+please
+see
+[Design Doc: Operation Graph Based Parameter Server](./dist_train.md)
+
+## Distributed Training Architecture
+
+The new distributed training architecture can address the above
+limitations. Below is the illustration:
+
+<img src="src/distributed_architecture.png"/>
+
+The architecture includes major components: *PaddlePaddle Python*,
+*PaddlePaddle converter* and *PaddlePaddle runtime*:
+
+### PaddlePaddle Python
+
+PaddlePaddle Python is the Python library that user's Python trainer
+invoke to build the neural network topology, start training, etc.
+
+```Python
+paddle.init()
+input = paddle.op.recordIO("/home/data/mnist.recordio") # file stored on the cluster
+img, label = input[0], input[1]
+hidden = paddle.layer.fc(input=img, size=200, act=paddle.activation.Tanh())
+prediction = paddle.layer.fc(input=img, size=10, act=paddle.activation.Softmax())
+cost = paddle.layer.classification_cost(input=prediction, label=label)
+optimizer = paddle.optimizer.SGD(cost, learning_rate=0.01)
+session = paddle.session.NewRemote(num_trainer=3, num_ps=2, GPU_per_trainer=1)
+for i in range(1000):
+	_, cost_val = session.eval(targets=[cost, optimizer])
+	print cost_val
+```
+
+The code above is a typical Python trainer code, the neural network
+topology is built using helper functions such as
+`paddle.layer.fc`. The training is done by calling `session.eval`
+iteratively.
+
+#### session.eval
+
+As shown in the graph, `session.eval` sends the IR and the evaluation
+inputs/targets to the PaddlePaddle cluster for evaluation. The
+targets can be any variable in the computation graph. When the target
+is the `optimizer` variable, the neural network will be optimized
+once. When the target is the `cost` variable, `session.eval` returns
+the cost value.
+
+The Python `session` is a wrapper of the C++ `Session` class. For more
+information about `Session`, please
+see [Design Doc: Session](./session.md).
+
+### PaddlePaddle Converter
+
+PaddlePaddle converter automatically converts the IR in the request
+(IR and evaluation inputs/targets) from PaddlePaddle Python to new
+partitioned IRs and dispatch the new IRs and evaluation inputs/targets
+to different PaddlePaddle runtimes. Below are the steps:
+
+1. Add `feed` OP that feeds the eval inputs, and `fetch` OP that
+   fetches the eval targets to the IR.
+
+1. Extract a new computation (sub)graph with `feed` and `fetch` OP as
+   the boundary. The runtime does not need to run the OP that is not
+   dependent by the `fetch` OP.
+
+1. Optimizes the computation graph.
+
+1. Place the OPs in the graph onto different devices on different
+   PaddlePaddle runtime according to a placement algorithm and device
+   constraint specified by the user.
+
+1. Partition the graph according to runtime boundaries and add `send` /
+   `recv` OP pair on the runtime boundaries.
+
+1. Dispatch the partitioned graph to different PaddlePaddle runtimes.
+
+1. PaddlePaddle runtimes with the `fetch` OP reports evaluation
+   results back to the converter, the convert reports the evaluation
+   results back to the PaddlePaddle Python.
+   
+The output IRs will be cached to optimize the conversion latency.
+
+
+#### Placement Algorithm
+
+Our first implementation will only support "trainer-parameter server"
+placement: the parameters, initializers, and optimizers are placed on
+the PaddlePaddle runtimes with the parameter server role. And
+everything else will be placed on the PaddlePaddle runtimes with the
+trainer role. This has the same functionality of our
+"trainer-parameter server" architecture of PaddlePaddle v0.10.0, but
+is more general and flexible.
+
+In the future, we will implement the general placement algorithm,
+which makes placements according to the input IR, and a model of
+device computation time and device communication time. Model
+parallelism requires the general placement algorithm.
+
+
+### PaddlePaddle Runtime
+
+The PaddlePaddle runtime owns multiple devices (e.g., CPUs, GPUs) and
+runs the IR. The runtime does not need to do OP placement since it's
+already done by the converter.
+
+
+### Local Training Architecture
+
+The local training architecture will be the same as the distributed
+training architecture, the differences are everything runs locally,
+and there is just one PaddlePaddle runtime:
+
+<img src="src/local_architecture.png"/>
+
+
+### Training Data
+
+In PaddlePaddle v0.10.0, training data is typically read
+with [data reader](../reader/README.md) from Python. This approach is
+no longer efficient when training distributedly since the Python
+process no longer runs on the same node with the trainer processes,
+the Python reader will need to read from the distributed filesystem
+(assuming it has the access) and send to the trainers, doubling the
+network traffic.
+
+When doing distributed training, the user can still use Python data
+reader: the training data are sent with `session.eval`. However should
+be used for debugging purpose only. The users are encouraged to use
+the read data OPs.
+
+
+## References:
+
+[1] [TensorFlow: Large-Scale Machine Learning on Heterogeneous Distributed Systems](https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/45166.pdf)
+
+[2] [TensorFlow: A System for Large-Scale Machine Learning](https://www.usenix.org/system/files/conference/osdi16/osdi16-abadi.pdf)

doc/design/refactor/session.md

+# Design Doc: Session
+
+## Abstract
+
+The *session* object encapsulates the environment in which the
+computation graph is executed.
+
+We will have the *local* session and *remote* session, they offer the
+same [interface](#interface). The local session encapsulates the local
+runtime environment and the remote session encapsulates the cluster
+runtime environment.
+
+The local runtime environment contains:
+
+1. computation devices (i.e., CPU, GPU) handles, and
+1. the [scope](../scope.md) which holds all variables.
+
+The remote runtime environment contains:
+
+1. computation devices (i.e., CPU and GPU on node 0, 1) in a cluster,
+   and
+1. the distributed [scope](../scope.md) in a cluster which holds all
+   variables.
+
+The user can create a remote session on Paddle Cloud and evaluate the
+computation graph with it. In this way, the user can control the
+remote computation resource in a cluster from his local computer.
+
+
+## Background
+
+The current design has an implicit global session in which
+`paddle.eval()` is executed. The pain point is:
+
+Since the user is not able to explicitly switch between runtime
+environments, the user cannot run a topology in two independent
+environments.
+
+For example, in reinforcement learning, the user may want to have a
+stale model for inference and a fresh model for training, and only
+replace the stale model with the fresh model periodically.
+
+Furthermore, we have no concept that encapsulates a remote environment
+that executes a computation graph.
+
+We need the session object to address above issues.
+
+
+## Session
+
+A session is an object that owns the runtime environment. All
+computations are executed through `session.eval()`.
+
+
+### Interface
+
+```python
+eval(
+    targets,
+    feed_dict=None,
+)
+```
+
+Evaluates the target Operations or Variables in `targets`.
+
+- *targets*: the evaluation targets. Can be a single Operation or
+  Variable, or a list with the Operations or Variables as
+  elements. The value returned by `eval()` has the same shape as the
+  `target` argument.
+
+  The PaddlePaddle program is represented by
+  the [ProgramDesc](../design/program.md), `eval()` will infer the
+  ProgramDesc from the given targets and run the PaddlePaddle
+  program. Please
+  see
+  [this graph](./distributed_architecture.md#local-training-architecture) for
+  the detailed illustration for the local session
+  and
+  [this graph](./distributed_architecture.md#distributed-training-architecture) for
+  the detailed illustration for the remote session.
+
+- *feed_dict*: a dictionary that contains the tensors which override
+  the edges of the computation graph.
+
+  feed_dict not only can provide the input data, it can override any
+  OP's input as well:
+
+  ```python
+  a = pd.constant(2.0, name="a")
+  b = pd.variable(name="b")
+  c = pd.mul(a,b)
+  sess.eval(targets=c, feed_dict={"b":3.0}) # returns 6.0
+  ```
+
+```python
+close()
+```
+
+Closes the session and releases the scope that the session owns.
+
+
+### Create a Local Session
+
+```python
+session(
+    devices=None
+)
+```
+
+Creates a new session. One session owns one global scope, so creating
+multiple sessions will create different scopes.
+
+- *devices*: a single `string` or a list of `string` of device names,
+  the corresponding devices will be the computation devices for
+  `eval()`. If not specified, all available devices (e.g., all GPUs)
+  will be used. The user doesn't need to specify the CPU device since
+  it will be always used. Multiple sessions can use the same device.
+
+
+#### Example
+
+```Python
+a = paddle.constant(1.0)
+b = paddle.constant(2.0)
+c = a + b
+sess = paddle.session(devices=["gpu:0", "gpu:1", "fpga:0"])
+sess.eval(c)
+sess.close()
+```
+
+### Create a Remote Session
+
+```python
+create_cloud_job(
+    name,
+    num_trainer,
+    mem_per_trainer,
+    gpu_per_trainer,
+    cpu_per_trainer,
+    num_ps,
+    mem_per_ps,
+    cpu_per_ps,
+)
+```
+
+Creates a Paddle Cloud job. Fails if the job name exists.
+
+```python
+get_cloud_job(
+    name
+)
+```
+
+Gets a Paddle Cloud job.
+
+```python
+remote_session(
+    job
+)
+```
+
+- *job*: the Paddle Cloud job.
+
+#### Example
+
+```Python
+reader = paddle.reader.recordio("/pfs/home/peter/mnist-train-*") # data stored on Paddle Cloud
+image = reader.column(0)
+label = reader.column(1)
+fc1 = paddle.op.fc(image, size=256, act="sigmoid")
+fc2 = paddle.op.fc(fc1, size=10, act="softmax")
+cost = paddle.op.cross_entropy(fc2, label)
+opt = paddle.optimizer.sgd(cost)
+
+job = paddle.create_cloud_job("test", 3, "1G", 1, 1, 2, "1G", 1)
+sess = paddle.remote_ession(job)
+for i in range(1000):
+    sess.eval(opt)
+sess.close()
+```

doc/design/refactorization.md

 # Design Doc: Refactorization Overview
 
-The goal of refactorizaiton include:
+The goals of refactoring include:
 
-1. Make it easy for external contributors to write new elementory computaiton operations.
-1. Make the codebase clean and readable.
-1. Introduce a new design of computation representation -- a computation graph of operators and variables.
-1. The graph representation helps implementing auto-scalable and auto fault recoverable distributed computing.
+1. Making it easy for external contributors to write new elementary computation operations.
+1. Making the codebase clean and readable.
+1. Designing a new computation representation -- a computation graph of operators and variables.
+1. Implementing auto-scalability and auto fault recoverable distributed computing with the help of computation graphs.
 
 ## Computation Graphs
 
-1. PaddlePaddle represent the computation, training and inference of DL models, by computation graphs.
+1. PaddlePaddle represents the computation, training and inference of Deep Learning models, by computation graphs.
 
-  1. Please dig into [computation graphs](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/graph.md) for a solid example.
+  1. Please refer to [computation graphs](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/graph.md) for a concrete example.
 
-1. Users write Python programs to describe the graphs and run it (locally or remotely).
+1. Users write Python programs to describe the graphs and run them (locally or remotely).
 
 1. A graph is composed of *variables* and *operators*.
 
-1. The description of graphs must be able to be serialized/deserialized, so it
+1. The description of graphs must be serializable/deserializable, so that:
 
-   1. could to be sent to the cloud for distributed execution, and
-   1. be sent to clients for mobile or enterprise deployment.
+   1. It can be sent to the cloud for distributed execution, and
+   1. It can be sent to clients for mobile or enterprise deployment.
 
-1. The Python program do
+1. The Python program does two things
 
-   1. *compilation*: runs a Python program to generate a protobuf message representation of the graph and send it to
+   1. *Compilation* runs a Python program to generate a protobuf message representation of the graph and send it to
       1. the C++ library `libpaddle.so` for local execution,
       1. the master process of a distributed training job for training, or
       1. the server process of a Kubernetes serving job for distributed serving.
-   1. *execution*: according to the protobuf message, constructs instances of class `Variable` and `OperatorBase`, and run them.
+   1. *Execution* executes the graph by constructing instances of class [`Variable`](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/variable.h#L24) and [`OperatorBase`](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/operator.h#L70), according to the protobuf message.
 
-## Description and Realization
+## Description and Realization of Computation Graph
 
-At compile time, the Python program generates protobuf message representation of the graph, or the description of the graph.
+At compile time, the Python program generates a protobuf message representation of the graph, or a description of the graph.
 
-At runtime, the C++ program realizes the graph and run it.
+At runtime, the C++ program realizes the graph and runs it.
 
 | | Representation (protobuf messages) | Realization (C++ class objects) |
 |---|---|---|
@@ -42,30 +42,31 @@ At runtime, the C++ program realizes the graph and run it.
 |Operation|[OpDesc](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/framework.proto#L35)|[Operator](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/operator.h#L64)|
 |Block|BlockDesc|Block|
 
-The word *graph* is exchangable with *block* in this document.  A graph represent computation steps and local variables as a C++/Java program block, or a pair of { and }.
+The word *graph* is interchangeable with *block* in this document.  A graph consists of computation steps and local variables similar to a C++/Java program block, or a pair of parentheses(`{` and `}`).
 
 ## Compilation and Execution
 
-1. Run an applicaton Python program to describe the graph.  In particular,
+1. Run a Python program to describe the graph.  In particular, the Python application program does the following:
 
-   1. create VarDesc to represent local/intermediate variables,
-   1. create operators and set attributes,
-   1. validate attribute values,
-   1. inference the type and the shape of variables,
-   1. plan for memory-reuse for variables,
-   1. generate backward and optimization part of the Graph.
-   1. possiblly split the graph for distributed training.
+   1. Create `VarDesc` to represent local/intermediate variables,
+   1. Create operators and set attributes,
+   1. Validate attribute values,
+   1. Infer the type and the shape of variables,
+   1. Plan memory-reuse for variables,
+   1. Generate the backward graph
+   1. Add optimization operators to the computation graph.
+   1. Optionally, split the graph for distributed training.
 
-1. The invocation of `train` or `infer` in the application Python program:
+1. The invocation of `train` or [`infer`](https://github.com/PaddlePaddle/Paddle/blob/develop/python/paddle/v2/inference.py#L108) methods in the Python program does the following:
 
-   1. create a new Scope instance in the [scope hierarchy](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/scope.md) for each run of a block,
+   1. Create a new Scope instance in the [scope hierarchy](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/design/scope.md) for each run of a block,
       1. realize local variables defined in the BlockDesc message in the new scope,
       1. a scope is similar to the stack frame in programming languages,
 
-   1. create an instance of class `Block`, in which,
+   1. Create an instance of class `Block`, in which,
       1. realize operators in the BlockDesc message,
 
-   1. run the Block by calling
+   1. Run the Block by calling
       1. `Block::Eval(vector<Variable>* targets)` for forward and backward computations, or
       1. `Block::Eval(vector<Operator>* targets)` for optimization.
 
@@ -76,14 +77,14 @@ The word *graph* is exchangable with *block* in this document.  A graph represen
 Compile Time -> IR -> Runtime
 ```
 
-### Benefit
+### Benefits of IR
 
 - Optimization
   ```text
   Compile Time -> IR -> Optimized IR -> Runtime
   ```
-- Send automatically partitioned IR to different nodes.
-  - Automatic data parallel
+- Automatically send partitioned IR to different nodes.
+  - Automatic Data Parallelism
     ```text
     Compile Time
     |-> Single GPU IR
@@ -92,7 +93,7 @@ Compile Time -> IR -> Runtime
             |-> Node-1 (runs trainer-IR-1)
             |-> Node-2 (runs pserver-IR)
     ```
-  - Automatic model parallel (planned for future)
+  - Automatic Model Parallelism (planned for future)
 
 ---
 
@@ -105,10 +106,10 @@ Compile Time -> IR -> Runtime
 # Operator
 ![class_diagram](http://api.paddlepaddle.org/graphviz?dot=https://gist.githubusercontent.com/reyoung/53df507f6749762675dff3e7ce53372f/raw/dd598e8f1976f5759f58af5e5ef94738a6b2e661/op.dot)
 
-* `Operator` is the fundamental building block as the user interface.
-    * Operator stores input/output variable name, and attributes.
-    * The `InferShape` interface is used to infer output variable shapes by its input shapes.
-    * Use `Run` to compute `input variables` to `output variables`.
+* `Operator` is the fundamental building block of the user interface.
+    * Operator stores input/output variable names and attributes.
+    * The `InferShape` interface is used to infer the shape of the output variables based on the shapes of the input variables.
+    * Use `Run` to compute the `output` variables from the `input` variables.
 
 ---
 
@@ -126,30 +127,29 @@ Compile Time -> IR -> Runtime
 # Why separate Kernel and Operator
 
 * Separate GPU and CPU code.
-    * Make Paddle can run without GPU.
-* Make one operator (which is user interface) can contain many implementations.
-    * Same mul op, different FP16, FP32 Kernel. different MKL, eigen kernel.
+    * Make Paddle capable of running without GPU.
+* Make one operator (which is a user interface) and create many implementations.
+    * For example, same multiplication op can have different implementations kernels such as FP16 kernel, FP32 kernel, MKL, eigen kernel.
 ---
 
 # Libraries for Kernel development
 
 * `Eigen::Tensor` contains basic math and element-wise functions.
     * Note that `Eigen::Tensor` has broadcast implementation.
-    * Limit number of `tensor.device(dev) = ` in your code.
-* `thrust::tranform` and `std::transform`.
-    * `thrust` has the same API as C++ standard library. Using `transform` can quickly implement a customized elementwise kernel.
-    * `thrust` has more complex API, like `scan`, `reduce`, `reduce_by_key`.
+    * Limit the number of `tensor.device(dev) = ` in your code.
+* `thrust::transform` and `std::transform`.
+    * `thrust` has the same API as C++ standard library. Using `transform`, one can quickly implement customized element-wise kernels.
+    * `thrust`, in addition, supports more complex APIs, like `scan`, `reduce`, `reduce_by_key`.
 * Hand-writing `GPUKernel` and `CPU` code
-    * Do not write `.h`. CPU Kernel should be in `.cc`. GPU kernel should be in `.cu`. (`GCC` cannot compile GPU code.)
+    * Do not write in header (`.h`) files. CPU Kernel should be in cpp source (`.cc`) and GPU kernels should be in cuda (`.cu`) files. (GCC cannot compile GPU code.)
 ---
-# Operator Register
+# Operator Registration
 
-## Why register is necessary?
+## Why is registration necessary?
 We need a method to build mappings between Op type names and Op classes.
 
-## How to do the register?
-
-Maintain a map, whose key is the type name and value is corresponding Op constructor.
+## How is registration implemented?
+Maintaining a map, whose key is the type name and the value is the corresponding Op constructor.
 
 ---
 # The Registry Map
@@ -169,7 +169,7 @@ Maintain a map, whose key is the type name and value is corresponding Op constru
 # Related Concepts
 
 ### Op_Maker
-It's constructor takes `proto` and `checker`. They are compeleted during Op_Maker's construction. ([ScaleOpMaker](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/scale_op.cc#L37))
+It's constructor takes `proto` and `checker`. They are completed during Op_Maker's construction. ([ScaleOpMaker](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/scale_op.cc#L37))
 
 ### Register Macros
 ```cpp
@@ -177,34 +177,35 @@ REGISTER_OP(op_type, op_class, op_maker_class, grad_op_type, grad_op_class)
 REGISTER_OP_WITHOUT_GRADIENT(op_type, op_class, op_maker_class)
 ```
 
-### `USE` Macros
-make sure the registration process is executed and linked.
+### USE Macros
+Make sure the registration process is executed and linked.
 
 ---
-# Register Process
-1. Write Op class, as well as its gradient Op class if there is.
-2. Write Op maker class. In the constructor, describe its inputs, outputs, and attributes.
-3. Invoke macro `REGISTER_OP`. The macro will
-	1. call maker class to complete `proto` and `checker`
-	2. with the completed `proto` and `checker`, build a new key-value pair in the `OpInfoMap`
+# Registration Process
+1. Write an Op class and its gradient Op class, if required.
+2. Write an Op maker class. In the constructor of this class, describe the inputs, outputs and attributes of the operator.
+3. Invoke the macro `REGISTER_OP`. This macro will
+	1. Call maker class to complete `proto` and `checker`
+	2. Using the completed `proto` and `checker`, it will add a new key-value pair to the `OpInfoMap`
 
-4. Invoke `USE` macro in where the Op is used to make sure it is linked.
+4. Invoke the `USE` macro in which the Op is used to make sure that it is linked.
 
 ---
 # Backward Module (1/2)
 ### Create Backward Operator
-- Mapping from forwarding Op to backward Op
+- Mapping from forward Op to backward Op
 ![backward](https://gist.githubusercontent.com/dzhwinter/a6fbd4623ee76c459f7f94591fd1abf0/raw/61026ab6e518e66bde66a889bc42557a1fccff33/backward.png)
 
 ---
 # Backward Module (2/2)
 ### Build Backward Network
-- **Input** graph of forwarding operators
-- **Output** graph of backward operators
-- **corner case in construction**
-	- shared variable => insert `Add` operator
-	- no gradient => insert `fill_zero_grad` operator
-	- recursive netOp => call `Backward` recursively
+- **Input**: a graph of forward operators
+- **Output**: a graph of backward operators
+- **Corner cases in construction**
+	- Shared Variables => insert an `Add` operator to combine gradients
+	- No Gradient => insert a `fill_zero_grad` operator
+	- Recursive NetOp => call `Backward` recursively
+	- RNN Op => recursively call `Backward` on stepnet
 	- RNN Op => recursively call `Backward` on stepnet
 
 
@@ -213,41 +214,41 @@ make sure the registration process is executed and linked.
 
 * `Tensor` is an n-dimension array with type.
 	* Only dims and data pointers are stored in `Tensor`.
-	* All operators on `Tensor` is written in `Operator` or global functions.
-	* variable length Tensor design [LoDTensor](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/lod_tensor.md)
-* `Variable` is the inputs and outputs of an operator. Not just `Tensor`.
-	* step_scopes in RNN is a variable and not a tensor.
-* `Scope` is where variables store at.
-	* map<string/*var name */, Variable>
-	* `Scope` has a hierarchical structure. The local scope can get variable from its parent scope.
+	* All operations on `Tensor` are written in `Operator` or global functions.
+	* Variable length Tensor design [LoDTensor](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/lod_tensor.md)
+* `Variable` instances are the inputs and the outputs of an operator, not just `Tensor`.
+	* `step_scopes` in RNN is a variable and not a tensor.
+* `Scope` is where variables are stored.
+	* map<string `var name`, Variable>
+	* `Scope` has a hierarchical structure. The local scope can get variables from its parent scope.
 
 ---
 # Block (in design)
-## the difference with original RNNOp
-- as an operator is more intuitive than `RNNOp`,
-- offers new interface `Eval(targets)` to deduce the minimal block to `Run`,
-- fits the compile-time/ runtime separation design.
-  - during the compilation, `SymbolTable` stores `VarDesc`s and `OpDesc`s and serialize to a `BlockDesc`
-  - when graph executes, a Block with `BlockDesc` passed in creates `Op` and `Var` then `Run`
+## the difference between original RNNOp and Block
+- As an operator is more intuitive than `RNNOp`,
+- Offers a new interface `Eval(targets)` to deduce the minimal block to `Run`,
+- Fits the compile-time/ runtime separation design paradigm.
+  - During the compilation, `SymbolTable` stores `VarDesc`s and `OpDesc`s and serialize to a `BlockDesc`
+  - When graph executes, a Block with `BlockDesc` is passed. It then creates `Op` and `Var` instances and then invokes `Run`.
 
 ---
 # Milestone
-- take Paddle/books as the main line, the requirement of the models motivates framework refactoring,
-- model migration
-  - framework development gives **priority support** to model migration, for example,
+- Take Paddle/books as the main line, the requirement of the models motivates framework refactoring,
+- Model migration
+  - Framework development gives **priority support** to model migration, for example,
     - the MNIST demo needs a Python interface,
     - the RNN models require the framework to support `LoDTensor`.
-  - determine some timelines,
-  - heavily-relied Ops need to be migrated first,
-  - different models can be migrated parallelly.
-- improve the framework at the same time
-- accept imperfection, concentrated on solving the specific problem at the right price.
+  - Determine some timelines,
+  - Frequently used Ops need to be migrated first,
+  - Different models can be migrated in parallel.
+- Improve the framework at the same time
+- Accept imperfection, concentrate on solving the specific problem at the right price.
 
 ---
 # Control the migration quality
-- compare the performance of migrated models with old ones.
-- follow google C style
-- build the automatic workflow of generating Python/C++ documentations
-  - the documentation of layers and ops should be written inside the code
-  - take the documentation quality into account when doing PR
-  - preview the documentations, read and improve them from users' perspective
+- Compare the performance of migrated models with old ones.
+- Follow the google C++ style guide.
+- Build the automatic workflow of generating Python/C++ documentations.
+  - The documentation of layers and ops should be written inside the code.
+  - Take the documentation quality into account when submitting pull requests.
+  - Preview the documentations, read and improve them from a user's perspective.

doc/design/register_grad_op.md

+# Design Doc: Gradient Operators Registration
+
+
+## The Problem Posed
+
+Currently, for each C++ operator class definition, there registers a *gradient operator creator* function, which takes a C++ operator instance and returns the corresponding gradient operator instance.
+
+However, we noticed two problems with the current deisgn:
+
+1. As we decided to separate the *compilation* and *execution* phases, we need to change the creator to take an `OpDesc` protobuf message in a `ProgramDesc` and inserts corresponding `OpDesc` messages into the `ProgramDesc` message.
+
+1. Some operator's gradient computation requires more than one gradient operators.  For example, the gradient of *minus* consists of two operators -- an identity operaotr and a scale operator.  So we need to make the registration mechanism to support the mapping from an operator to a set of operators for gradient computation.
+
+## The Current Implementation
+
+The C++ class `OpInfos` store in a association map which key is the operator type. The `grad_op_type` indicate associated gradient operator type. Operator can create gradient operator by `OpInfo::creator_` of gradient. The pseudo code is
+
+```cpp
+struct OpInfo {
+  std::function<OperatorBase*(...)> creator_;
+  std::string grad_op_type_;
+  ...
+};
+
+map<string, OpInfo> OpInfoMap;
+
+OperatorBase* CreateGradientOperator(const OperatorBase& op) {
+  return OpInfoMap.at(op.Type()).creator_(...);
+}
+```
+
+## Proposed Solution
+
+The mapping relationship between an operator and its gradient operators is a function. The interface of that function is:
+
+```cpp
+// (OpDesc) --> vector<OpDesc>
+std::function<std::vector<OpDescBind>(const OpDescBind&)>;
+```
+
+The function takes an `OpDescBind` of the forward operator and returns one or many gradient operator descriptions. `OpDescBind` is a C++ wrapper for protobuf message `OpDesc` to manipulate `OpDesc` fast.
+
+The `GradOpDescMaker` will be registered in `OpInfo`, to replace `grad_op_type_` field. The `OpInfo` should be
+
+```cpp
+struct OpInfo {
+  std::function<std::vector<std::unique_ptr<OpDescBind>>(const OpDescBind&)>  grad_op_maker_;
+  ...
+};
+```
+
+The `grad_op_maker_ ` is `nullptr` if the operator does not have associated gradient operators.
+
+We propose a base class called `GradOpDescMakerBase` to let operator developers generate `Gradient Operators` easily. The public interface of that class is
+
+```cpp
+class GradOpDescMakerBase {
+public:
+  GradOpDescMakerBase(const OpDescBind& );
+  virtual std::vector<std::unique_ptr<OpDescBind>> operator()()const = 0;
+};
+```
+
+We can convert `GradOpDescMakerBase` to `std::function<std::vector<std::unique_ptr<OpDescBind>>(const OpDescBind&)>` by
+
+```cpp
+using GradOpMaker = ...;
+std::function<std::vector<OpDescBind>(const OpDescBind&)> func;
+func = [] (const OpDescBind& fwd_op) {
+  GradOpMaker maker(fwd_op);
+  return maker();
+};
+```
+
+We can write many helper functions since the `GradOpDescMakerBase` is a class now. The basic helper functions get the variables of `Input`, `Output`, `InputGradient` and `OutputGradient` in the forwarding operator.
+
+We should chagne register macros at the same time. In the current solution, there is no difference between forwarding operators and backward operators. So `REGISTER_OP` just register one operator. If the `REGISTER_OPERATOR ` contains `OpProtoAndCheckerMaker` and `GradOpDescMaker`, we just list them in the same macro. It can be done by a macro contains `__VA_ARGS__`.
+
+The user interface should be
+
+```cpp
+vector<OpDesc> MinusOpGradMaker(OpDesc) {...}
+REGISTER_OPERATOR(minus, MinusOp, MinusOpProtoAndCheckerMaker, SumOpGradMaker);
+// Developers can still manually implement gradient operator.
+REGISTER_OPERATOR(minus_grad, MinusGradOp);
+```
+
+The interface of current `REGISTER_OP` macro could not be changed. In `REGISTER_OP`, it will invoke `REGISTER_OPERATOR` two times and generate GradOpDescMaker inside.
+
+```cpp
+REGISTER_OP(minus, MinusOp, MinusOpProtoAndCheckerMaker, minus_grad, MinusGradOp);
+```

doc/design/scope.md

@@ -37,7 +37,7 @@ Scope is an association of a name to variable. All variables belong to `Scope`.
 ```cpp
 class Scope {
  public:
-  Variable* NewVar(const std::string& name);
+  Variable* Var(const std::string& name);
   const Variable* FindVar(const std::string& name) const;
 
  private:
@@ -98,7 +98,7 @@ class Scope {
   Variable* FindVar(const std::string& name) const;
 
   // return if already contains same name variable.
-  Variable* NewVar(const std::string& name);
+  Variable* Var(const std::string& name);
 
  private:
   std::shared_ptr<Scope> parent_;
@@ -107,7 +107,7 @@ class Scope {
 ```
 ## Only scope can create a variable
 
-To ensure `only scope can create a variable`, we should mark `Variable`'s constructor as a private member function, and Scope is a friend class of Variable. And then only `NewVar` can construct `Variable`.
+To ensure `only scope can create a variable`, we should mark `Variable`'s constructor as a private member function, and Scope is a friend class of Variable. And then only `Var` can construct `Variable`.
 
 ## When scope destroyed, all variables inside this scope should be destroyed together
 
@@ -121,4 +121,4 @@ Also, as the parent scope is a `shared_ptr`, we can only `Create()` a scope shar
 
 ## Orthogonal interface
 
-`FindVar` will return `nullptr` when `name` is not found. It can be used as `Contains` method. `NewVar` will return an `Error` when there is a name conflict locally. Combine `FindVar` and `NewVar`, we can implement `NewVar` easily.
+`FindVar` will return `nullptr` when `name` is not found. It can be used as `Contains` method. `Var` will return an `Error` when there is a name conflict locally. Combine `FindVar` and `Var`, we can implement `Var` easily.

doc/design/selected_rows.md

+# Design Doc: Selected Rows
+
+`SelectedRows` is a type of sparse tensor data type, which is designed to support `embedding` operators. The gradient of embedding table is a sparse tensor. Only a few rows are non-zero values in this tensor. It is straight-forward to represent a sparse tensor by the following sparse tensor data structure:
+
+```cpp
+class SelectedRows {
+ private:
+  vector<int> rows_;
+  Tensor value_;
+  int height_;
+};
+```
+
+The field `height_` is the first dimension of `SelectedRows`. The `rows` are the indices of the non-zero rows of `SelectedRows`. The `value_` field is an N-dim tensor of shape `[rows.size() /* NUM_ROWS */, ...]`, which supplies values for each row. The dimension of `SelectedRows` satisfies `[height_] + value_.shape[1:]`.
+
+Suppose that a SelectedRows-typed variable `x` has many rows, but only two of them have values -- row 73 is `[1, 2]` and row 84 is `[3, 4]`, the `SelectedRows` representation would be:
+
+```
+x = SelectedRow {
+  rows = [73, 84],
+  value = [[1, 2], [3,4]]
+}
+```
+
+
+## SelectedRows in Protobuf
+
+`SelectedRows` is a type of `Variable`. `VarDesc` in protobuf should describe the `SelectedRows` information. Only the tensor dimension of a `SelectedRows` will be described in compile-time because the `rows_` and `value_` are dependent on the training data. 
+So we use `TensorDesc` to unify `data_type` and `dims`. A LodTensorDesc contains a `TensorDesc` and `lod_level`. The description of `SelectedRows` is a Tensor description.
+
+```proto
+message TensorDesc {
+  required DataType data_type = 1;
+  repeated int64 dims = 2; // [UNK, 640, 480] is saved as [-1, 640, 480]
+}
+
+message LodTensorDesc {
+  required TensorDesc tensor = 1;
+  optional int lod_level = 2;
+}
+
+message VarDesc {
+  required string name = 1;
+  enum VarType { 
+    LOD_TENSOR = 0;
+    SELECTED_ROWS = 1;
+  }
+  required VarType type = 2;
+  optional LodTensorDesc lod_desc = 3;
+  optional TensorDesc selected_rows_desc = 4;
+  optional bool persistable = 5 [ default = false ];
+}
+```
+
+## InferShape for Selected Rows
+
+Just like `LoD` information, `InferShape` method will infer the output tensor type as well. The operator should decide whether its output is a `SelectedRows` or `Dense` tensor.
+
+For example, the gradient operator of `TableLookup` will always generate `SelectedRows`. Its `InferShape` method should be like following
+
+```cpp
+void TableLookupGrad::InferShape(context) {
+  ...
+  context.SetDataType("Embedding.Grad", kSelectedRows);
+}
+```
+
+
+## Sparse Operators
+
+There are several operators that need to be written to support `SelectedRows`. These are:
+
+1. Operators which generate `SelectedRows` gradient. e.g. Gradient of `TableLookupOp`.
+2. Optimize operators which support `SelectedRows` gradient. e.g. `SGD` or `AdaGrad` for `SelectedRows`. However, there should be only one `SGD` operator. `OpWithKernel::Run` should select a suitable kernel for both `dense` tensor or `SelectedRows`.

doc/design/tensor_array.md

+# Design for TensorArray
+This design doc presents the necessity of a new C++ class `TensorArray`.
+In addition to the very simple C++ implementation
+
+```c++
+class TensorArray {
+ public:
+  explicit TensorArray(const LoDTensor&);
+  explicit TensorArray(size_t size);
+
+ private:
+  vector<LoDTensor> values_;
+};
+```
+
+We also need to expose it to PaddlePaddle's Python API,
+because users would want to use it with our very flexible operators `WhileLoop`.
+An example for a RNN based on dynamic operators is 
+
+```python
+input = pd.data(...)
+num_steps = Var(12)
+
+TensorArray states(size=num_steps)
+TensorArray step_inputs(unstack_from=input)
+TensorArray step_outputs(size=num_steps)
+
+W = Tensor(...)
+U = Tensor(...)
+default_state = some_op()
+
+step = Var(1)
+
+wloop = paddle.create_whileloop(loop_vars=[step])
+with wloop.frame():
+    wloop.break_if(pd.equal(step, num_steps)
+    pre_state = states.read(step-1, default_state)
+    step_input = step_inputs.read(step)
+    state = pd.sigmoid(pd.matmul(U, pre_state) + pd.matmul(W, step_input))
+    states.write(step, state)
+    step_outputs.write(step, state) # output state
+    step.update(state+1)
+
+output = step_outputs.stack()
+```
+
+## Background
+Steps are one of the core concepts of RNN. In each time step of RNN, there should be several input segments, states, and output segments; all these components act like arrays, for example, call `states[step_id]` will get the state in `step_id`th time step.
+
+An RNN can be implemented with the following pseudocode
+
+```c++
+Array states;
+Array input_segments;
+Array output_segments;
+Parameter W, U;
+
+step = 1
+seq_len = 12
+while_loop {
+   if (step == seq_len) break;
+    states[step] = sigmoid(W * states[step-1] + U * input_segments[step]);
+    output_segments[step] = states[step] // take state as output
+   step++;
+}
+```
+According to the [RNN roadmap](https://github.com/PaddlePaddle/Paddle/issues/4561), there are several different RNNs that PaddlePaddle will eventually support.
+
+Currently, the basic RNN implementation supported by PaddlePaddle is the `recurrent_op` which takes tensors as input and splits them into `input_segments`.
+
+
+Since a tensor cannot store variable-length sequences directly, PaddlePaddle implements the tensor with level of details (`LoDTensor` for short).
+Segmenting the `LoDTensor` is much more complicated than splitting a tensor, that makes it necessary to refactor the `recurrent_op` with `LoDTensor` segmenting support.
+
+As the next step in RNN support, `dynamic_recurrent_op` should be introduced to handle inputs with variable-length sequences.
+
+The implementation is similar to `recurrent_op`. 
+The key difference is the way **the original input `LoDTensors` and outupts are split to get the `input_segments` and the `output_segments`.**
+
+
+Though it can't be built over `recurrent_op` or `dynamic_recurrent_op` directly,
+the logic behind splitting a tensor or a LoD tensor into `input_segments` remains the same.
+
+## Why `TensorArray`
+The logic behind splitting the inputs to segments, states and outputs is similar and can be shared in a seperate module.
+
+The array of `states`, `input_segments` and `output_segments` would be exposed to users when writing a dynamic RNN model similar to the above pseudo codes. 
+
+So there should be an array-like container, which can store the segments of a tensor or LoD tensor.
+
+**This container can store an array of tensors and provides several methods to split a tensor or a LoD tensor** .
+This is where the notion of `TensorArray` comes from.
+
+## Introduce TensorArray to uniform all the three RNNs
+TensorArray as a new concept is borrowed from TensorFlow, 
+it is meant to be used with dynamic iteration primitives such as `while_loop` and `map_fn`.
+
+This concept can be used to support our new design of dynamic operations, and help to refactor some existing variant-sentence-related layers, 
+such as `recurrent_op`, `RecurrentGradientMachine`.
+
+In [our design for dynamic RNN](https://github.com/PaddlePaddle/Paddle/pull/4401), 
+`TensorArray` is used to segment inputs and store states in all time steps.
+By providing some methods similar to a C++ array,
+the definition of some state-based dynamic models such as RNN can be more natural and highly flexible.
+
+## Dynamic-operations on TensorArray
+
+`TensorArray` will be used directly when defining dynamic models, so some operators listed below should be implemented
+
+```python
+# several helper operators for TensorArray
+def tensor_array_stack(ta, tensor):
+    '''
+    get a tensor array `ta`, return a packed `tensor`.
+    '''
+    pass
+
+def tensor_array_unstack(tensor, ta):
+    '''
+    get a `tensor`, unstack it and get a tensor array `ta`.
+    '''
+    pass
+
+def tensor_array_write(ta, index, tensor, data_shared):
+    '''
+    get a `tensor` and a scalar tensor `index`, write `tensor` into index-th
+    value of the tensor array `ta`.
+    `data_shared` is an attribute that specifies whether to copy or reference the tensors.
+    '''
+    pass
+
+def tensor_array_read(ta, index, tensor):
+    '''
+    get a tensor array `ta`, a scalar tensor `index`, read the index-th value of
+    `ta` and return as the `tensor`.
+    '''
+    pass
+
+def tensor_array_size(ta, tensor):
+    '''
+    get a tensor array `ta`, return the size of `ta` and return as the scalar `tensor`.
+    '''
+    pass
+```
+
+It is trivial for users to use so many low-level operators, so some helper methods should be proposed in python wrapper to make `TensorArray` easier to use, 
+for example
+
+```python
+class TensorArray:
+    def __init__(self, name):
+        self.name = name
+        self.desc = TensorArrayDesc()
+
+    def stack(self, name=None):
+        '''
+        Pack the values in a `TensorArray` into a tensor with rank one higher
+        than each tensor in `values`.
+        `stack` can be used to split tensor into time steps for RNN or whileloop.
+
+        @name: str
+            the name of the variable to output.
+        '''
+        tensor = Var(name)
+        tensor_array_stack(self.name, tensor)
+        return tensor
+
+    def unstack(self, input):
+        '''
+        Unpacks the given dimension of a rank-`R` tensor into rank-`(R-1)` tensors.
+        `unstack` can be used to concatenate all the time steps for RNN or whileloop.
+
+        @input: str
+            the name of input tensor
+        '''
+        tensor_array_unstack(tensor, self.name)
+
+    def write(self, index, value, data_shared=True):
+        '''
+        Write value into index of the TensorArray.
+        If `data_shared` is set to True, than the index-th value in TensorArray will
+        be shared with the tensor passed in.
+
+        @index: str
+            name of a scalar tensor
+        @value: str
+            name of a tensor
+        @data_shared: bool
+        '''
+        tensor_array_write(self.name, index, value, data_shared)
+
+    def read(self, index, output):
+        '''
+        Read the value at location `index` in the `TensorArray`.
+
+        @index: str
+            name of a scalar tensor
+        @output:
+            name of a output variable
+        '''
+        tensor_array_read(self.name, index, output)
+
+
+    def size(self, output):
+        '''
+        Return the number of values.
+
+        @output: str
+            name of a scalar tensor
+        '''
+        tensor_array_size(self.name, output)
+```
+
+## LoDTensor-related Supports
+The `RecurrentGradientMachine` in Paddle serves as a flexible RNN layer; it takes varience-length sequences as input, and output sequences too.
+
+Since each step of RNN can only take a tensor-represented batch of data as input, 
+some preprocess should be taken on the inputs such as sorting the sentences by their length in descending order and cut each word and pack to new batches.
+
+Such cut-like operations can be embedded into `TensorArray` as general methods called `unpack` and `pack`,
+these two operations are similar to `stack` and `unstack` except that they operate on variable-length sequences formated as a LoD tensor rather than a tensor.
+
+Some definitions are like
+
+```python
+def unpack(level):
+    '''
+    Split LodTensor in some `level` and generate batches, if set `sort_by_length`,
+    will sort by length.
+
+    Returns:
+        - a new `TensorArray`, whose values are LodTensors and represents batches
+          of data.
+        - an int32 Tensor, which stores the map from the new batch's indices to
+          original LoDTensor
+    '''
+    pass
+
+def pack(level, indices_map):
+    '''
+    Recover the original LoD-arranged LoDTensor with the values in a `TensorArray`
+    and `level` and `indices_map`.
+    '''
+    pass
+```
+
+With these two methods, a varience-length sentence supported RNN can be implemented like
+
+```c++
+// input is the varient-length data
+LodTensor sentence_input(xxx);
+TensorArray ta;
+Tensor indice_map;
+Tensor boot_state = xxx; // to initialize rnn's first state
+TensorArray::unpack(input, 1/*level*/, true/*sort_by_length*/, &ta, &indice_map);
+TessorArray step_outputs;
+TensorArray states;
+
+for (int step = 0; step = ta.size(); step++) {
+  auto state = states.read(step);
+  // rnnstep is a function which acts like a step of RNN
+  auto step_input = ta.read(step);
+  auto step_output = rnnstep(step_input, state);
+  step_outputs.write(step_output, true/*data_shared*/);
+}
+
+// rnn_output is the final output of an rnn
+LoDTensor rnn_output = ta.pack(ta, indice_map);
+```
+the code above shows that by embedding the LoDTensor-related preprocess operations into `TensorArray`,
+the implementation of a RNN that supports varient-length sentences is far more concise than `RecurrentGradientMachine` because the latter mixes all the codes together, hard to read and extend.

doc/design/test.dot

+
+digraph Test {
+    z -> generator -> G_img;
+    G_img -> discriminator -> D_f -> d_loss_f;
+    label0 -> d_loss_f -> d_loss;
+
+    img -> discriminator -> D_t -> d_loss_t;
+    label1 -> d_loss_t -> d_loss;
+
+    d_loss -> d_loss_t[color=red, style=dashed];
+    d_loss -> d_loss_f[color=red, style=dashed];
+    d_loss_t -> D_t[color=red, style=dashed];
+    d_loss_f -> D_f[color=red, style=dashed];
+    D_t -> discriminator[color=red, style=dashed];
+    D_f -> discriminator[color=red, style=dashed];
+
+    D_f -> g_loss;
+    label2 -> g_loss;
+
+    g_loss -> D_f[color=green, style=dashed];
+    D_f -> discriminator[color=green, style=dashed];
+    discriminator -> G_img[color=green, style=dashed];
+    G_img -> generator[color=green, style=dashed];
+
+    discriminator [color=red, shape=box];
+    generator [color=green, shape=box];
+    z [shape=diamond];
+    img [shape=diamond];
+    label0 [shape=diamond];
+    label1 [shape=diamond];
+    label2 [shape=diamond];
+
+    d_loss [color=red];
+    g_loss [color=green];
+}

doc/design/var_desc.md

@@ -16,16 +16,23 @@ The computation graph is constructed by Data Node and Operation Node. The concep
 
 ## Definition of VarDesc
 
-A VarDesc should have a name and value, in PaddlePaddle, the value will always be a tensor. Since we use LoDTensor most of the time. We add a LoDTesnorDesc to represent it.
+A VarDesc should have a name, and value. The are two kinds of variable type in compile time, they are `LoDTensor` and `SelectedRows`. 
 
 ```proto
 message VarDesc {
   required string name = 1;
-  optional LoDTensorDesc lod_tensor = 2;
+  enum VarType {
+    LOD_TENSOR = 0;
+    SELECTED_ROWS = 1;
+  }
+  required VarType type = 2;
+  optional LoDTensorDesc lod_desc = 3;
+  optional TensorDesc selected_rows_desc = 4;
+  optional bool persistable = 5 [ default = false ];
 }
 ```
 
-## Definition of LodTensorDesc
+## Definition of TensorDesc
 
 ```proto
 enum DataType {
@@ -38,87 +45,25 @@ enum DataType {
   FP64 = 6;
 }
 
-message LoDTensorDesc {
+message TensorDesc {
   required DataType data_type = 1;
-  repeated int32 dims = 2; // [UNK, 640, 480] is saved as [-1, 640, 480]
-  optional int32 lod_level = 3 [default=0];
+  repeated int64 dims = 2; // [UNK, 640, 480] is saved as [-1, 640, 480]
 }
 ```
 
-## Definition of Variable in Python
-
-In Python API, layer will take Variable as Input, and return Variable as Output. There should be a class `Variable` in python to help create and manage Variable.
-
-```python
-image = Variable(dims=[-1, 640, 480])
-# fc1 and fc2 are both Variable
-fc1 = layer.fc(input=image, output_size=10)
-fc2 = layer.fc(input=fc1, output_size=20)
-```
-### what should class `Variable` Have
-1. `name`.a name of string type is used to mark the value of the Variable.
-1. `initializer`. Since our Tensor does not have value. we will always use some Operator to fullfill it when run. So we should have a initialize method to help add the init operator.
-1. `operator`. Variable should record which operator produce itself. The reaon is:
-  - we use pd.eval(targets=[var1, var2]) to run the related ops to get the value of var1 and var2. var.op is used to trace the dependency of the current variable.
-
-In PaddlePaddle, we use Block to describe Computation Graph, so in the code we will use Block but not Graph.
-
-```python
-import VarDesc
-import LoDTensorDesc
-import framework
-
-def AddInitialOperator(variable, initializer):
-	# add an initialize Operator to block to init this Variable
-
-class Variable(object):
-   def __init__(self, name, dims, type, initializer):
-      self._block = get_default_block()
-      self._name = name
-      self.op = None
-
-      tensor_desc = LoDTensorDesc(data_type=type, dims=dims)
-      _var_desc = VarDesc(name=name, lod_tensor=tensor_desc)
-      self._var = framework.CreateVar(_var_desc)
-      self._block.add_var(self)
+A TensorDesc describes `SelectedRows` and `LoDTensor`. For details of `SelectedRows`, please reference [`SelectedRows`](./selected_rows.md).
 
-      # add initial op according to initializer
-      if initializer is not None:
-          AddInitialOperator(self, initializer)
-
-   def dims(self):
-      return self._var.dims()
-
-   def data_type(self):
-       return self._var.data_type()
+## Definition of LodTensorDesc
 
-   def to_proto(self):
-       pass
+```proto
+message LoDTensorDesc {
+  required TensorDesc tensor = 1;
+  optional int lod_level = 2;
+}
 ```
 
-Then we can use this Variable to create a fc layer in Python.
+A LoDTensorDesc contains a tensor and a lod_level.
 
-```python
-import paddle as pd
-
-def flatten_size(X, num_flatten_dims):
-  prod = 1 # of last num_flatten_dims
-  for i in xrange(num_flatten_dims):
-    prod = prod * X.dims[-i-1]
-  return prod
-
-def layer.fc(X, output_size, num_flatten_dims):
-  W = Variable(pd.random_uniform(), type=FP32, dims=[flatten_size(X, num_flatten_dims), output_size])
-  b = Variable(pd.random_uniform(), type=FP32, dims=[output_size])
-  out = Variable(type=FP32)
-  y = operator.fc(X, W, b, output=out) # fc will put fc op input into out
-  pd.InferShape(y)
-  return out
-
-x = Variable(dims=[-1, 640, 480])
-y = layer.fc(x, output_size=100)
-z = layer.fc(y, output_size=200)
+## Definition of Variable in Python
 
-paddle.eval(targets=[z], ...)
-print(z)
-```
+For Variable in Python, please reference [`Python API`](./python_api.md).

doc/faq/build_and_install/index_cn.rst

+###################
+编译安装与单元测试
+###################
+
+..  contents::
+
+1. 运行Docker GPU镜像出现 "CUDA driver version is insufficient"
+----------------------------------------------------------------
+
+用户在使用PaddlePaddle GPU的Docker镜像的时候，常常出现 `Cuda Error: CUDA driver version is insufficient for CUDA runtime version`, 原因在于没有把机器上CUDA相关的驱动和库映射到容器内部。
+具体的解决方法是：
+
+..  code-block:: bash
+
+    $ export CUDA_SO="$(\ls usr/lib64/libcuda* | xargs -I{} echo '-v {}:{}') $(\ls /usr/lib64/libnvidia* | xargs -I{} echo '-v {}:{}')"
+    $ export DEVICES=$(\ls /dev/nvidia* | xargs -I{} echo '--device {}:{}')
+    $ docker run ${CUDA_SO} ${DEVICES} -it paddledev/paddlepaddle:latest-gpu
+
+更多关于Docker的安装与使用, 请参考 `PaddlePaddle Docker 文档 <http://www.paddlepaddle.org/doc_cn/build_and_install/install/docker_install.html>`_ 。
+
+
+2. CMake源码编译, 找到的PythonLibs和PythonInterp版本不一致
+----------------------------------------------------------------
+
+这是目前CMake寻找Python的逻辑存在缺陷，如果系统安装了多个Python版本，CMake找到的Python库和Python解释器版本可能有不一致现象，导致编译PaddlePaddle失败。正确的解决方法是，
+用户强制指定特定的Python版本，具体操作如下：
+
+    ..  code-block:: bash
+
+        cmake .. -DPYTHON_EXECUTABLE=<exc_path> -DPYTHON_LIBRARY=<lib_path>  -DPYTHON_INCLUDE_DIR=<inc_path>
+
+用户需要指定本机上Python的路径：``<exc_path>``, ``<lib_path>``, ``<inc_path>``
+
+3. CMake源码编译，Paddle版本号为0.0.0
+--------------------------------------
+
+如果运行 :code:`paddle version`, 出现 :code:`PaddlePaddle 0.0.0`；或者运行 :code:`cmake ..`，出现
+
+..  code-block:: bash
+
+    CMake Warning at cmake/version.cmake:20 (message):
+      Cannot add paddle version from git tag
+
+那么用户需要拉取所有的远程分支到本机，命令为 :code:`git fetch upstream`，然后重新cmake即可。
+
+4. paddlepaddle\*.whl is not a supported wheel on this platform.
+------------------------------------------------------------------------
+
+出现这个问题的主要原因是，没有找到和当前系统匹配的paddlepaddle安装包。最新的paddlepaddle python安装包支持Linux x86_64和MacOS 10.12操作系统，并安装了python 2.7和pip 9.0.1。
+
+更新 :code:`pip` 包的方法是\:
+
+..  code-block:: bash
+
+    pip install --upgrade pip
+
+如果还不行，可以执行 :code:`python -c "import pip; print(pip.pep425tags.get_supported())"` 获取当前系统支持的python包的后缀，
+并对比是否和正在安装的后缀一致。
+
+如果系统支持的是 :code:`linux_x86_64` 而安装包是 :code:`manylinux1_x86_64` ，需要升级pip版本到最新；
+如果系统支持 :code:`manylinux1_x86_64` 而安装包（本地）是 :code:`linux_x86_64` ，可以重命名这个whl包为 :code:`manylinux1_x86_64` 再安装。
+
+5. 编译安装后执行 import paddle.v2 as paddle 报ImportError: No module named v2
+------------------------------------------------------------------------------------------
+先查看一下是否曾经安装过paddle v1版本，有的话需要先卸载：
+
+pip uninstall py_paddle paddle
+
+然后安装paddle的python环境, 在build目录下执行
+
+pip install python/dist/paddle*.whl && pip install ../paddle/dist/py_paddle*.whl
+
+6. 遇到“非法指令”或者是“illegal instruction”
+--------------------------------------------
+
+PaddlePaddle使用avx SIMD指令提高cpu执行效率，因此错误的使用二进制发行版可能会导致这种错误，请选择正确的版本。
+
+7.  python相关的单元测试都过不了
+--------------------------------
+
+如果出现以下python相关的单元测试都过不了的情况：
+
+..  code-block:: bash
+
+    24 - test_PyDataProvider (Failed)
+    26 - test_RecurrentGradientMachine (Failed)
+    27 - test_NetworkCompare (Failed)
+    28 - test_PyDataProvider2 (Failed)
+    32 - test_Prediction (Failed)
+    33 - test_Compare (Failed)
+    34 - test_Trainer (Failed)
+    35 - test_TrainerOnePass (Failed)
+    36 - test_CompareTwoNets (Failed)
+    37 - test_CompareTwoOpts (Failed)
+    38 - test_CompareSparse (Failed)
+    39 - test_recurrent_machine_generation (Failed)
+    40 - test_PyDataProviderWrapper (Failed)
+    41 - test_config_parser (Failed)
+    42 - test_swig_api (Failed)
+    43 - layers_test (Failed)
+
+并且查询PaddlePaddle单元测试的日志，提示：
+
+..  code-block:: bash
+
+    paddle package is already in your PYTHONPATH. But unittest need a clean environment.
+    Please uninstall paddle package before start unittest. Try to 'pip uninstall paddle'.
+
+解决办法是：
+
+* 卸载PaddlePaddle包 :code:`pip uninstall paddle`, 清理掉老旧的PaddlePaddle安装包，使得单元测试有一个干净的环境。如果PaddlePaddle包已经在python的site-packages里面，单元测试会引用site-packages里面的python包，而不是源码目录里 :code:`/python` 目录下的python包。同时，即便设置 :code:`PYTHONPATH` 到 :code:`/python` 也没用，因为python的搜索路径是优先已经安装的python包。

doc/faq/cluster/index_cn.rst

+###############
+集群训练与预测
+###############
+
+..  contents::
+
+1. 集群多节点训练，日志中保存均为网络通信类错误
+------------------------------------------------
+
+集群多节点训练，日志报错为网络通信类错误，比如 :code:`Connection reset by peer` 等。
+此类报错通常是由于某一个节点的错误导致这个节点的训练进程退出，从而引发其他节点无法连接导致，可以参考下面的步骤排查：
+
+* 从 :code:`train.log` ， :code:`server.log` 找到最早报错的地方，查看是否是其他错误引发的报错（比如FPE，内存不足，磁盘空间不足等）。
+
+* 如果发现最早的报错就是网络通信的问题，很有可能是非独占方式执行导致的端口冲突，可以联系OP，看当前MPI集群是否支持resource=full参数提交，如果支持增加此参数提交，并更换job 端口。
+
+* 如果当前MPI集群并不支持任务独占模式，可以联系OP是否可以更换集群或升级当前集群。

doc/faq/local/index_cn.rst

+###############
+本地训练与预测
+###############
+
+..  contents::
+
+1. 如何减少内存占用
+-------------------
+
+神经网络的训练本身是一个非常消耗内存和显存的工作，经常会消耗数10GB的内存和数GB的显存。
+PaddlePaddle的内存占用主要分为如下几个方面\:
+
+* DataProvider缓冲池内存（只针对内存）
+* 神经元激活内存（针对内存和显存）
+* 参数内存 （针对内存和显存）
+* 其他内存杂项
+
+其中，其他内存杂项是指PaddlePaddle本身所用的一些内存，包括字符串分配，临时变量等等，暂不考虑在内。
+
+减少DataProvider缓冲池内存
+++++++++++++++++++++++++++
+
+PyDataProvider使用的是异步加载，同时在内存里直接随即选取数据来做Shuffle。即
+
+..  graphviz::
+
+    digraph {
+        rankdir=LR;
+        数据文件 -> 内存池 -> PaddlePaddle训练
+    }
+
+所以，减小这个内存池即可减小内存占用，同时也可以加速开始训练前数据载入的过程。但是，这
+个内存池实际上决定了shuffle的粒度。所以，如果将这个内存池减小，又要保证数据是随机的，
+那么最好将数据文件在每次读取之前做一次shuffle。可能的代码为
+
+..  literalinclude:: src/reduce_min_pool_size.py
+
+这样做可以极大的减少内存占用，并且可能会加速训练过程，详细文档参考 :ref:`api_pydataprovider2` 。
+
+神经元激活内存
+++++++++++++++
+
+神经网络在训练的时候，会对每一个激活暂存一些数据，如神经元激活值等。
+在反向传递的时候，这些数据会被用来更新参数。这些数据使用的内存主要和两个参数有关系，
+一是batch size，另一个是每条序列(Sequence)长度。所以，其实也是和每个mini-batch中包含
+的时间步信息成正比。
+
+所以做法可以有两种：
+
+* 减小batch size。 即在网络配置中 :code:`settings(batch_size=1000)` 设置成一个小一些的值。但是batch size本身是神经网络的超参数，减小batch size可能会对训练结果产生影响。
+* 减小序列的长度，或者直接扔掉非常长的序列。比如，一个数据集大部分序列长度是100-200,
+  但是突然有一个10000长的序列，就很容易导致内存超限，特别是在LSTM等RNN中。
+
+参数内存
+++++++++
+
+PaddlePaddle支持非常多的优化算法(Optimizer)，不同的优化算法需要使用不同大小的内存。
+例如使用 :code:`adadelta` 算法，则需要使用等于权重参数规模大约5倍的内存。举例，如果参数保存下来的模型目录
+文件为 :code:`100M`， 那么该优化算法至少需要 :code:`500M` 的内存。
+
+可以考虑使用一些优化算法，例如 :code:`momentum`。
+
+2. 如何加速训练速度
+-------------------
+
+加速PaddlePaddle训练可以考虑从以下几个方面\：
+
+* 减少数据载入的耗时
+* 加速训练速度
+* 利用分布式训练驾驭更多的计算资源
+
+减少数据载入的耗时
+++++++++++++++++++
+
+使用\ :code:`pydataprovider`\ 时，可以减少缓存池的大小，同时设置内存缓存功能，即可以极大的加速数据载入流程。
+:code:`DataProvider` 缓存池的减小，和之前减小通过减小缓存池来减小内存占用的原理一致。
+
+..  literalinclude:: src/reduce_min_pool_size.py
+
+同时 :code:`@provider` 接口有一个 :code:`cache` 参数来控制缓存方法，将其设置成 :code:`CacheType.CACHE_PASS_IN_MEM` 的话，会将第一个 :code:`pass` (过完所有训练数据即为一个pass)生成的数据缓存在内存里，在之后的 :code:`pass` 中，不会再从 :code:`python` 端读取数据，而是直接从内存的缓存里读取数据。这也会极大减少数据读入的耗时。
+
+
+加速训练速度
+++++++++++++
+
+PaddlePaddle支持Sparse的训练，sparse训练需要训练特征是 :code:`sparse_binary_vector` 、 :code:`sparse_vector` 、或者 :code:`integer_value` 的任一一种。同时，与这个训练数据交互的Layer，需要将其Parameter设置成 sparse 更新模式，即设置 :code:`sparse_update=True`
+
+这里使用简单的 :code:`word2vec` 训练语言模型距离，具体使用方法为\:
+
+使用一个词前两个词和后两个词，来预测这个中间的词。这个任务的DataProvider为\:
+
+..  literalinclude:: src/word2vec_dataprovider.py
+
+这个任务的配置为\:
+
+..  literalinclude:: src/word2vec_config.py
+
+
+利用更多的计算资源
+++++++++++++++++++
+
+利用更多的计算资源可以分为一下几个方式来进行\:
+
+* 单机CPU训练
+
+  * 使用多线程训练。设置命令行参数 :code:`trainer_count`。
+
+* 单机GPU训练
+
+  * 使用显卡训练。设置命令行参数 :code:`use_gpu`。
+  * 使用多块显卡训练。设置命令行参数 :code:`use_gpu` 和 :code:`trainer_count` 。
+
+* 多机训练
+
+  * 请参考 :ref:`cluster_train` 。
+
+3. 如何指定GPU设备
+------------------
+
+例如机器上有4块GPU，编号从0开始，指定使用2、3号GPU：
+
+* 方式1：通过 `CUDA_VISIBLE_DEVICES <http://www.acceleware.com/blog/cudavisibledevices-masking-gpus>`_ 环境变量来指定特定的GPU。
+
+..      code-block:: bash
+
+        env CUDA_VISIBLE_DEVICES=2,3 paddle train --use_gpu=true --trainer_count=2
+
+* 方式2：通过命令行参数 ``--gpu_id`` 指定。
+
+..      code-block:: bash
+
+        paddle train --use_gpu=true --trainer_count=2 --gpu_id=2
+
+
+4. 训练过程中出现 :code:`Floating point exception`, 训练因此退出怎么办?
+------------------------------------------------------------------------
+
+Paddle二进制在运行时捕获了浮点数异常，只要出现浮点数异常(即训练过程中出现NaN或者Inf)，立刻退出。浮点异常通常的原因是浮点数溢出、除零等问题。
+主要原因包括两个方面:
+
+* 训练过程中参数或者训练过程中的梯度尺度过大，导致参数累加，乘除等时候，导致了浮点数溢出。
+* 模型一直不收敛，发散到了一个数值特别大的地方。
+* 训练数据有问题，导致参数收敛到了一些奇异的情况。或者输入数据尺度过大，有些特征的取值达到数百万，这时进行矩阵乘法运算就可能导致浮点数溢出。
+
+这里有两种有效的解决方法：
+
+1. 设置 :code:`gradient_clipping_threshold` 参数，示例代码如下：
+
+..  code-block:: python
+
+optimizer = paddle.optimizer.RMSProp(
+    learning_rate=1e-3,
+    gradient_clipping_threshold=10.0,
+    regularization=paddle.optimizer.L2Regularization(rate=8e-4))
+
+具体可以参考  `nmt_without_attention  <https://github.com/PaddlePaddle/models/blob/develop/nmt_without_attention/train.py#L35>`_ 示例。
+
+2. 设置 :code:`error_clipping_threshold` 参数，示例代码如下：
+
+..  code-block:: python
+
+decoder_inputs = paddle.layer.fc(
+    act=paddle.activation.Linear(),
+    size=decoder_size * 3,
+    bias_attr=False,
+    input=[context, current_word],
+    layer_attr=paddle.attr.ExtraLayerAttribute(
+        error_clipping_threshold=100.0))
+
+完整代码可以参考示例 `machine translation <https://github.com/PaddlePaddle/book/blob/develop/08.machine_translation/train.py#L66>`_ 。
+
+两种方法的区别：
+
+1. 两者都是对梯度的截断，但截断时机不同，前者在 :code:`optimzier` 更新网络参数时应用；后者在激活函数反向计算时被调用；
+2. 截断对象不同：前者截断可学习参数的梯度，后者截断回传给前层的梯度;
+
+除此之外，还可以通过减小学习律或者对数据进行归一化处理来解决这类问题。
+
+5.  如何调用 infer 接口输出多个layer的预测结果
+-----------------------------------------------
+
+* 将需要输出的层作为 :code:`paddle.inference.Inference()` 接口的 :code:`output_layer` 参数输入，代码如下：
+
+..  code-block:: python
+
+    inferer = paddle.inference.Inference(output_layer=[layer1, layer2], parameters=parameters)
+
+* 指定要输出的字段进行输出。以输出 :code:`value` 字段为例，代码如下：
+
+..  code-block:: python
+
+    out = inferer.infer(input=data_batch, field=["value"])
+
+需要注意的是：
+
+* 如果指定了2个layer作为输出层，实际上需要的输出结果是两个矩阵；
+* 假设第一个layer的输出A是一个 N1 * M1 的矩阵，第二个 Layer 的输出B是一个 N2 * M2 的矩阵；
+* paddle.v2 默认会将A和B 横向拼接，当N1 和 N2 大小不一样时，会报如下的错误：
+
+..      code-block:: python
+
+    ValueError: all the input array dimensions except for the concatenation axis must match exactly
+
+多个层的输出矩阵的高度不一致导致拼接失败，这种情况常常发生在：
+
+* 同时输出序列层和非序列层；
+* 多个输出层处理多个不同长度的序列;
+
+此时可以在调用infer接口时通过设置 :code:`flatten_result=False` , 跳过“拼接”步骤，来解决上面的问题。这时，infer接口的返回值是一个python list:
+
+* list 中元素的个数等于网络中输出层的个数；
+* list 中每个元素是一个layer的输出结果矩阵，类型是numpy的ndarray；
+* 每一个layer输出矩阵的高度，在非序列输入时：等于样本数；序列输入时等于：输入序列中元素的总数；宽度等于配置中layer的size；

doc/faq/model/index_cn.rst

+#########
+模型配置
+#########
+
+..  contents::
+
+1. 出现 :code:`Duplicated layer name` 错误怎么办
+--------------------------------------------------
+
+出现该错误的原因一般是用户对不同layer的参数 :code:`name` 设置了相同的取值。遇到该错误时，先找出参数 :code:`name` 取值相同的layer，然后将这些layer的参数 :code:`name` 设置为不同的值。
+
+2. :code:`paddle.layer.memory` 的参数 :code:`name` 如何使用
+-------------------------------------------------------------
+
+* :code:`paddle.layer.memory` 用于获取特定layer上一时间步的输出，该layer是通过参数 :code:`name` 指定，即，:code:`paddle.layer.memory` 会关联参数 :code:`name` 取值相同的layer，并将该layer上一时间步的输出作为自身当前时间步的输出。
+
+* PaddlePaddle的所有layer都有唯一的name，用户通过参数 :code:`name` 设定，当用户没有显式设定时，PaddlePaddle会自动设定。而 :code:`paddle.layer.memory` 不是真正的layer，其name由参数 :code:`memory_name` 设定，当用户没有显式设定时，PaddlePaddle会自动设定。:code:`paddle.layer.memory` 的参数 :code:`name` 用于指定其要关联的layer，需要用户显式设定。
+
+3. 两种使用 drop_out 的方法有何区别
+------------------------------------
+
+* 在PaddlePaddle中使用dropout有两种方式
+
+  * 在相应layer的 :code:`layer_atter` 设置 :code:`drop_rate`，以 :code:`paddle.layer.fc` 为例，代码如下：
+
+  ..  code-block:: python
+
+      fc = paddle.layer.fc(input=input, layer_attr=paddle.attr.ExtraLayerAttribute(drop_rate=0.5))
+
+  * 使用 :code:`paddle.layer.dropout`，以 :code:`paddle.layer.fc` 为例，代码如下：
+
+  ..  code-block:: python
+
+      fc = paddle.layer.fc(input=input)
+      drop_fc = paddle.layer.dropout(input=fc, dropout_rate=0.5)
+
+* :code:`paddle.layer.dropout` 实际上使用了 :code:`paddle.layer.add_to`，并在该layer里采用第一种方式设置 :code:`drop_rate` 来使用dropout的。这种方式对内存消耗较大。
+
+* PaddlePaddle在激活函数里实现dropout，而不是在layer里实现。
+
+* :code:`paddle.layer.lstmemory`、:code:`paddle.layer.grumemory`、:code:`paddle.layer.recurrent` 不是通过一般的方式来实现对输出的激活，所以不能采用第一种方式在这几个layer里设置 :code:`drop_rate` 来使用dropout。若要对这几个layer使用dropout，可采用第二种方式，即使用 :code:`paddle.layer.dropout`。
+
+4. 不同的 recurrent layer 的区别
+----------------------------------
+以LSTM为例，在PaddlePaddle中包含以下 recurrent layer：
+
+* :code:`paddle.layer.lstmemory`
+* :code:`paddle.networks.simple_lstm`
+* :code:`paddle.networks.lstmemory_group`
+* :code:`paddle.networks.bidirectional_lstm`
+
+按照具体实现方式可以归纳为2类：
+
+1. 由 recurrent_group 实现的 recurrent layer：
+
+  * 用户在使用这一类recurrent layer时，可以访问由recurrent unit在一个时间步内计算得到的中间值（例如：hidden states, memory cells等）；
+  * 上述的 :code:`paddle.networks.lstmemory_group` 是这一类的 recurrent layer ；
+
+2. 将recurrent layer作为一个整体来实现：
+
+  * 用户在使用这一类recurrent layer，只能访问它们的输出值；
+  * 上述的 :code:`paddle.networks.lstmemory_group` 、 :code:`paddle.networks.simple_lstm` 和 :code:`paddle.networks.bidirectional_lstm` 属于这一类的实现；
+
+将recurrent layer作为一个整体来实现， 能够针对CPU和GPU的计算做更多优化， 所以相比于recurrent group的实现方式， 第二类 recurrent layer 计算效率更高。 在实际应用中，如果用户不需要访问LSTM的中间变量，而只需要获得recurrent layer计算的输出，我们建议使用第二类实现。
+
+此外，关于LSTM, PaddlePaddle中还包含 :code:`paddle.networks.lstmemory_unit` 这一计算单元：
+
+  * 不同于上述介绍的recurrent layer , :code:`paddle.networks.lstmemory_unit` 定义了LSTM单元在一个时间步内的计算过程，它并不是一个完整的recurrent layer，也不能接收序列数据作为输入；
+  * :code:`paddle.networks.lstmemory_unit` 只能在recurrent_group中作为step function使用；

doc/faq/parameter/index_cn.rst

+#########
+参数设置
+#########
+
+..  contents::
+
+1. 如何选择SGD算法的学习率
+--------------------------
+
+在采用sgd/async_sgd进行训练时，一个重要的问题是选择正确的learning_rate。如果learning_rate太大，那么训练有可能不收敛，如果learning_rate太小，那么收敛可能很慢，导致训练时间过长。
+
+通常做法是从一个比较大的learning_rate开始试，如果不收敛，那减少学习率10倍继续试验，直到训练收敛为止。那么如何判断训练不收敛呢？可以估计出如果模型采用不变的输出最小的cost0是多少。
+
+如果训练过程的的cost明显高于这个常数输出的cost，那么我们可以判断为训练不收敛。举一个例子，假如我们是三分类问题，采用multi-class-cross-entropy作为cost，数据中0,1,2三类的比例为 :code:`0.2, 0.5, 0.3` , 那么常数输出所能达到的最小cost是 :code:`-(0.2*log(0.2)+0.5*log(0.5)+0.3*log(0.3))=1.03` 。如果训练一个pass（或者更早）后，cost还大于这个数，那么可以认为训练不收敛，应该降低学习率。
+
+2. 如何设置学习率退火（learning rate annealing）
+------------------------------------------------
+
+在相应的优化算法里设置learning_rate_schedule及相关参数，以使用Adam算法为例，代码如下：
+
+..  code-block:: python
+
+    optimizer = paddle.optimizer.Adam(
+        learning_rate=1e-3,
+        learning_rate_decay_a=0.5,
+        learning_rate_decay_b=0.75,
+        learning_rate_schedule="poly",)
+
+PaddlePaddle目前支持8种learning_rate_schedule，这8种learning_rate_schedule及其对应学习率计算方式如下：
+
+* "constant"
+  
+  lr = learning_rate
+
+* "poly"
+
+  lr = learning_rate * pow(1 + learning_rate_decay_a * num_samples_processed, -learning_rate_decay_b)
+
+  其中，num_samples_processed为已训练样本数，下同。
+
+* "caffe_poly"
+
+  lr = learning_rate * pow(1.0 - num_samples_processed / learning_rate_decay_a, learning_rate_decay_b)
+
+* "exp"
+
+  lr = learning_rate * pow(learning_rate_decay_a, num_samples_processed / learning_rate_decay_b)
+
+* "discexp"
+
+  lr = learning_rate * pow(learning_rate_decay_a, floor(num_samples_processed / learning_rate_decay_b))
+
+* "linear"
+
+  lr = max(learning_rate - learning_rate_decay_a * num_samples_processed, learning_rate_decay_b)
+
+* "manual"
+
+  这是一种按已训练样本数分段取值的学习率退火方法。使用该learning_rate_schedule时，用户通过参数 :code:`learning_rate_args` 设置学习率衰减因子分段函数，当前的学习率为所设置 :code:`learning_rate` 与当前的衰减因子的乘积。以使用Adam算法为例，代码如下：
+
+  ..  code-block:: python
+
+      optimizer = paddle.optimizer.Adam(
+          learning_rate=1e-3,
+          learning_rate_schedule="manual",
+          learning_rate_args="1000:1.0,2000:0.9,3000:0.8",)
+
+  在该示例中，当已训练样本数小于等于1000时，学习率为 :code:`1e-3 * 1.0`；当已训练样本数大于1000小于等于2000时，学习率为 :code:`1e-3 * 0.9`；当已训练样本数大于2000时，学习率为 :code:`1e-3 * 0.8`。
+
+* "pass_manual"
+
+  这是一种按已训练pass数分段取值的学习率退火方法。使用该learning_rate_schedule时，用户通过参数 :code:`learning_rate_args` 设置学习率衰减因子分段函数，当前的学习率为所设置 :code:`learning_rate` 与当前的衰减因子的乘积。以使用Adam算法为例，代码如下：
+
+  ..  code-block:: python
+
+      optimizer = paddle.optimizer.Adam(
+          learning_rate=1e-3,
+          learning_rate_schedule="manual",
+          learning_rate_args="1:1.0,2:0.9,3:0.8",)
+
+  在该示例中，当已训练pass数小于等于1时，学习率为 :code:`1e-3 * 1.0`；当已训练pass数大于1小于等于2时，学习率为 :code:`1e-3 * 0.9`；当已训练pass数大于2时，学习率为 :code:`1e-3 * 0.8`。
+
+3. 如何初始化参数
+-----------------
+
+默认情况下，PaddlePaddle使用均值0，标准差为 :math:`\frac{1}{\sqrt{d}}` 来初始化参数。其中 :math:`d` 为参数矩阵的宽度。这种初始化方式在一般情况下不会产生很差的结果。如果用户想要自定义初始化方式，PaddlePaddle目前提供两种参数初始化的方式\:
+
+* 高斯分布。将 :code:`param_attr` 设置成 :code:`param_attr=ParamAttr(initial_mean=0.0, initial_std=1.0)`
+* 均匀分布。将 :code:`param_attr` 设置成 :code:`param_attr=ParamAttr(initial_max=1.0, initial_min=-1.0)`
+
+比如设置一个全连接层的参数初始化方式和bias初始化方式，可以使用如下代码。
+
+..  code-block:: python
+
+    hidden = fc_layer(input=ipt, param_attr=ParamAttr(initial_max=1.0, initial_min=-1.0),
+                      bias_attr=ParamAttr(initial_mean=1.0, initial_std=0.0))
+
+上述代码将bias全部初始化为1.0, 同时将参数初始化为 :code:`[1.0, -1.0]` 的均匀分布。
+
+4. 如何共享参数
+---------------
+
+PaddlePaddle的参数使用名字 :code:`name` 作为参数的ID，相同名字的参数，会共享参数。设置参数的名字，可以使用 :code:`ParamAttr(name="YOUR_PARAM_NAME")` 来设置。更方便的设置方式，是使得要共享的参数使用同样的 :code:`ParamAttr` 对象。
+
+简单的全连接网络，参数共享的配置示例为\:
+
+..  literalinclude:: ../../python/paddle/trainer_config_helpers/tests/configs/shared_fc.py
+
+这里 :code:`hidden_a` 和 :code:`hidden_b` 使用了同样的parameter和bias。并且softmax层的两个输入也使用了同样的参数 :code:`softmax_param`。
+
+5. 如何加载预训练参数
+------------------------
+
+* 对加载预训练参数的层，设置其参数属性 :code:`is_static=True`，使该层的参数在训练过程中保持不变。以embedding层为例，代码如下：
+
+..  code-block:: python
+
+    emb_para = paddle.attr.Param(name='emb', is_static=True)
+    paddle.layer.embedding(size=word_dim, input=x, param_attr=emb_para)
+
+
+* 从模型文件将预训练参数载入 :code:`numpy.array`，在创建parameters后，使用 :code:`parameters.set()` 加载预训练参数。PaddlePaddle保存的模型参数文件前16字节为头信息，用户将参数载入 :code:`numpy.array` 时须从第17字节开始。以embedding层为例，代码如下：
+
+..  code-block:: python
+
+    def load_parameter(file_name, h, w):
+        with open(file_name, 'rb') as f:
+            f.read(16)  # skip header.
+            return np.fromfile(f, dtype=np.float32).reshape(h, w)
+
+    parameters = paddle.parameters.create(my_cost)
+    parameters.set('emb', load_parameter(emb_param_file, 30000, 256))
+
+6. 存储的参数格式是什么，如何和明文进行相互转化
+--------------------------------------------------
+
+PaddlePaddle保存的模型参数文件内容由16字节头信息和网络参数两部分组成。头信息中，1~4字节表示PaddlePaddle版本信息，请直接填充0；5~8字节表示每个参数占用的字节数，当保存的网络参数为float类型时为4，double类型时为8；9~16字节表示保存的参数总个数。
+
+将PaddlePaddle保存的模型参数还原回明文时，可以使用相应数据类型的 :code:`numpy.array` 加载具体网络参数，此时可以跳过PaddlePaddle模型参数文件的头信息。若在PaddlePaddle编译时，未指定按照double精度编译，默认情况下按照float精度计算，保存的参数也是float类型。这时在使用 :code:`numpy.array` 时，一般设置 :code:`dtype=float32` 。示例如下：
+
+..  code-block:: python
+
+    def read_parameter(fname, width):
+        s = open(fname).read()
+        # skip header
+        vec = np.fromstring(s[16:], dtype=np.float32)
+        # width is the size of the corresponding layer
+        np.savetxt(fname + ".csv", vec.reshape(width, -1),
+                fmt="%.6f", delimiter=",")
+
+
+将明文参数转化为PaddlePaddle可加载的模型参数时，首先构造头信息，再写入网络参数。下面的代码将随机生成的矩阵转化为可以被PaddlePaddle加载的模型参数。
+
+..  code-block:: python
+
+    def gen_rand_param(param_file, width, height, need_trans):
+        np.random.seed()
+        header = struct.pack("iil", 0, 4, height * width)
+        param = np.float32(np.random.rand(height, width))
+        with open(param_file, "w") as fparam:
+            fparam.write(header + param.tostring())
+
+7. A protocol message was rejected because it was too big
+------------------------------------------------------------
+
+如果在训练NLP相关模型时，出现以下错误：
+
+..  code-block:: bash
+
+    [libprotobuf ERROR google/protobuf/io/coded_stream.cc:171] A protocol message was rejected because it was too big (more than 67108864 bytes).  To increase the limit (or to disable these warnings), see CodedInputStream::SetTotalBytesLimit() in google/protobuf/io/coded_stream.h.
+    F1205 14:59:50.295174 14703 TrainerConfigHelper.cpp:59] Check failed: m->conf.ParseFromString(configProtoStr)
+
+可能的原因是：传给dataprovider的某一个args过大，一般是由于直接传递大字典导致的。错误的define_py_data_sources2类似：
+
+..  code-block:: python
+
+     src_dict = dict()
+     for line_count, line in enumerate(open(src_dict_path, "r")):
+        src_dict[line.strip()] = line_count
+
+     define_py_data_sources2(
+        train_list,
+        test_list,
+        module="dataprovider",
+        obj="process",
+        args={"src_dict": src_dict})
+
+解决方案是：将字典的地址作为args传给dataprovider，然后在dataprovider里面根据该地址加载字典。即define_py_data_sources2应改为：
+
+..  code-block:: python
+
+     define_py_data_sources2(
+        train_list,
+        test_list,
+        module="dataprovider",
+        obj="process",
+        args={"src_dict_path": src_dict_path})
+
+完整源码可参考 `seqToseq <https://github.com/PaddlePaddle/Paddle/tree/develop/demo/seqToseq>`_ 示例。
+
+

doc/getstarted/build_and_install/docker_install_cn.rst

@@ -20,7 +20,7 @@ Docker使用入门
 		  
      docker pull paddlepaddle/paddle:0.10.0
 
-  来下载Docker镜像，paddlepaddle/paddle是从官方镜像源Dockerhub.com下载的，推荐国内用户使用ocker.paddlepaddle.org/paddle下载。
+  来下载Docker镜像，paddlepaddle/paddle是从官方镜像源Dockerhub.com下载的，推荐国内用户使用docker.paddlepaddle.org/paddle下载。
 
 - *容器*： 如果说一个Docker镜像就是一个程序，那容器就是这个程序运行时产生的“进程”。
   实际上，一个容器就是一个操作系统的进程，但是是运行在独立的进程空间，文件系统以及网络之上。

doc/howto/deep_model/rnn/rnn_config_cn.rst

@@ -21,7 +21,7 @@ wmt14数据的提供文件在 `python/paddle/v2/dataset/wmt14.py <https://github
 
 循环神经网络在每个时间步骤顺序地处理序列。下面列出了 LSTM 的架构的示例。
 
-.. image:: ../../../tutorials/sentiment_analysis/bi_lstm.jpg
+.. image:: src/bi_lstm.jpg
       :align: center
 
 一般来说，循环网络从 :math:`t=1` 到 :math:`t=T` 或者反向地从 :math:`t=T` 到 :math:`t=1` 执行以下操作。
@@ -96,7 +96,7 @@ Sequence to Sequence Model with Attention
 我们将使用 sequence to sequence model with attention
 作为例子演示如何配置复杂的循环神经网络模型。该模型的说明如下图所示。
 
-.. image:: ../../../tutorials/text_generation/encoder-decoder-attention-model.png
+.. image:: src/encoder-decoder-attention-model.png
       :align: center
 
 在这个模型中，源序列 :math:`S = \{s_1, \dots, s_T\}` 

doc/howto/deep_model/rnn/rnn_config_en.rst

@@ -19,7 +19,7 @@ Simple Gated Recurrent Neural Network
 
 Recurrent neural network process a sequence at each time step sequentially. An example of the architecture of LSTM is listed below.
 
-.. image:: ../../../tutorials/sentiment_analysis/src/bi_lstm.jpg
+.. image:: src/bi_lstm.jpg
      :align: center
 
 Generally speaking, a recurrent network perform the following operations from :math:`t=1` to :math:`t=T`, or reversely from :math:`t=T` to :math:`t=1`.
@@ -78,7 +78,7 @@ Sequence to Sequence Model with Attention
 -----------------------------------------
 We will use the sequence to sequence model with attention as an example to demonstrate how you can configure complex recurrent neural network models. An illustration of the sequence to sequence model with attention is shown in the following figure.
 
-.. image:: ../../../tutorials/text_generation/encoder-decoder-attention-model.png
+.. image:: src/encoder-decoder-attention-model.png
       :align: center
 
 In this model, the source sequence :math:`S = \{s_1, \dots, s_T\}` is encoded with a bidirectional gated recurrent neural networks. The hidden states of the bidirectional gated recurrent neural network :math:`H_S = \{H_1, \dots, H_T\}` is called *encoder vector* The decoder is a gated recurrent neural network. When decoding each token :math:`y_t`, the gated recurrent neural network generates a set of weights :math:`W_S^t = \{W_1^t, \dots, W_T^t\}`, which are used to compute a weighted sum of the encoder vector. The weighted sum of the encoder vector is utilized to condition the generation of the token :math:`y_t`.

doc/howto/dev/new_op_cn.md

@@ -206,7 +206,7 @@ MulOp(const std::string &type, const framework::VariableNameMap &inputs,
 
     - `REGISTER_OP` ： 注册`ops::MulOp`类，类型名为`mul`，该类的`ProtoMaker`为`ops::MulOpMaker`，注册`ops::MulOpGrad`，类型名为`mul_grad`。
     - `REGISTER_OP_WITHOUT_GRADIENT` ： 用于注册没有反向的Op。
-    - `REGISTER_OP_CPU_KERNEL` ：注册`ops::MulKernel`类，并特化模板参数为`paddle::platform::CPUPlace`和`float`类型，同理，注册`ops::MulKernel`类。
+    - `REGISTER_OP_CPU_KERNEL` ：注册`ops::MulKernel`类，并特化模板参数为`paddle::platform::CPUPlace`和`float`类型，同理，注册`ops::MulGradKernel`类。
 
 
 - 在 `.cu`文件中注册GPU Kernel。
@@ -285,41 +285,27 @@ class TestMulGradOp(GradientChecker):
             'Y': np.random.random((84, 100)).astype("float32")
         }
 
-    def test_cpu_gpu_compare(self):
-        self.compare_grad(self.op, self.inputs)
-
-    def test_normal(self):
+    def test_check_grad_normal(self):
         # mul op will enlarge the relative error
-        self.check_grad(
-            self.op, self.inputs, ["X", "Y"], "Out", max_relative_error=0.5)
+        self.check_grad(['X', 'Y'], 'Out', max_relative_error=0.5)
 
-    def test_ignore_x(self):
+    def test_check_grad_ingore_x(self):
         self.check_grad(
-            self.op,
-            self.inputs, ["Y"],
-            "Out",
-            max_relative_error=0.5,
-            no_grad_set={"X"})
+            ['Y'], 'Out', max_relative_error=0.5, no_grad_set=set("X"))
 
-    def test_ignore_y(self):
+    def test_check_grad_ingore_y(self):
         self.check_grad(
-            self.op,
-            self.inputs, ["X"],
-            "Out",
-            max_relative_error=0.5,
-            no_grad_set={"Y"})
+            ['X'], 'Out', max_relative_error=0.5, no_grad_set=set('Y'))
 ```
 
 下面解释代码中一些关键的地方:
 
 - 调用`create_op("mul")`创建反向Op对应的前向Op。
-- 调用`compare_grad`函数对比CPU、GPU计算结果。
-- `test_normal`中调用`check_grad`使用数值法检测梯度正确性和稳定性。
-  - 第一个参数`self.op` : 前向Op。
-  - 第二个参数`self.inputs` : 输入词典，词典的Key和`ProtoMaker`定义保持一致。
-  - 第三个参数`["X", "Y"]` : 指定对输入变量`X`、`Y`做梯度检测。
-  - 第四个参数`"Out"` : 指定前向网络最终的输出目标变量`Out`
-- `test_ignore_x`和`test_ignore_y`分支用来测试只需要计算一个输入梯度的情况。
+- `test_check_grad_normal`中调用`check_grad`使用数值法检测梯度正确性和稳定性。
+  - 第一个参数`["X", "Y"]` : 指定对输入变量`X`、`Y`做梯度检测。
+  - 第二个参数`"Out"` : 指定前向网络最终的输出目标变量`Out`。
+  - 第三个参数`max_relative_error`：指定检测梯度时能容忍的最大错误值。
+- `test_check_grad_ingore_x`和`test_check_grad_ingore_y`分支用来测试只需要计算一个输入梯度的情况。
 
 
 ### 编译和执行单元测试

doc/howto/dev/new_op_en.md

 # How to write a new operator
 
- - [Background](#Background)
- - [Implementing C++ Types](#Implementing_C++_Types)
-   - [Defining ProtoMaker](#Defining_ProtoMaker)
-   - [Defining Operator](#Defining_Operator)
-   - [Registering Operator](#Registering_Operator)
-   - [Compilation](#Compilation)
- - [Python Binding](#Python_Binding)
- - [Unit Tests](#Unit_Tests)
-
+ - [Background](#background)
+ - [Implementing C++ Types](#implementing-c++-types)
+   - [Defining ProtoMaker](#defining-protoMaker)
+   - [Defining Operator](#defining-operator)
+   - [Registering Operator](#registering-operator)
+   - [Compilation](#compilation)
+ - [Python Binding](#python-binding)
+ - [Unit Tests](#unit-tests)
+   - [Testing Forward Operators](#testing-forward-operators)
+   - [Testing Backward Operators](#testing-backward-operators)
+   - [Compiling and Running](#compiling-and-running)
+ - [Remarks](#remarks)
 ## Background
 
 Here are the base types needed. For details, please refer to the design docs.
@@ -179,7 +182,7 @@ Note that **different devices (CPU, GPU)share an Op definition; whether or not t
 
 `MulOp`'s CPU and GPU share the same `Kernel`. A non-sharing  `OpKernel` example can be seen in [`OnehotCrossEntropyOpKernel`](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/operators/cross_entropy_op.h#L43).
 
-To ease the writing of `OpKernel` compute, and for reusing code cross-device, `Eigen unsupported Tensor` module is used to implement `Compute` interface. To learn about how the Eigen library is used in PaddlePaddle, please see [usage document](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/howto/dev/use_eigen_cn.md).
+To ease the writing of `OpKernel` compute, and for reusing code cross-device, [`Eigen-unsupported Tensor`](https://bitbucket.org/eigen/eigen/src/default/unsupported/Eigen/CXX11/src/Tensor/README.md?fileviewer=file-view-default) module is used to implement `Compute` interface. To learn about how the Eigen library is used in PaddlePaddle, please see [usage document](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/howto/dev/use_eigen_cn.md).
 
 
 This concludes the forward implementation of an operator. Next its operation and kernel need to be registered in a `.cc` file.
@@ -202,7 +205,7 @@ The definition of its corresponding backward operator, if applicable, is similar
 
     - `REGISTER_OP` registers the `ops::MulOp` class, type named `mul`, its type `ProtoMaker` is `ops::MulOpMaker`, registering `ops::MulOpGrad` as `mul_grad`.
     - `REGISTER_OP_WITHOUT_GRADIENT` registers an operator without gradient.
-    - `REGISTER_OP_CPU_KERNEL` registers `ops::MulKernel` class and specialized template types `paddle::platform::CPUPlace` and `float`, which also registers `ops::MulKernel`.
+    - `REGISTER_OP_CPU_KERNEL` registers `ops::MulKernel` class and specialized template types `paddle::platform::CPUPlace` and `float`, which also registers `ops::MulGradKernel`.
 
 
 - Registering GPU Kernel in `.cu` files
@@ -232,4 +235,108 @@ The system will automatically bind to Python and link it to a generated library.
 
 ## Unit Tests
 
-Unit tests include comparing a forward operator's implementations on different devices, comparing a backward operator's implementation on different devices, and a scaling test for the backward operator. Here, we introduce the [unit tests for `MulOp`](https://github.com/PaddlePaddle/Paddle/blob/develop/python/paddle/v2/framework/tests/test_mul_op.py).
+Unit tests for an operator include
+
+1. comparing a forward operator's implementations on different devices,
+
+2. comparing a backward operator's implementation on different devices, and
+
+3. a scaling test for the backward operator.
+
+Here, we introduce the [unit tests for `MulOp`](https://github.com/PaddlePaddle/Paddle/blob/develop/python/paddle/v2/framework/tests/test_mul_op.py).
+
+### Testing Forward Operators
+
+A forward operator unit test inherits `unittest.TestCase` and defines metaclass `__metaclass__ = OpTestMeta`. More concrete tests are performed in `OpTestMeta`. Testing a forward operator requires the following:
+
+1. Defining input, output and relevant attributes in `setUp` method.
+
+2. Generating random input data.
+
+3. Implementing the same computation logic in a Python script:
+
+  ```python
+  import unittest
+  import numpy as np
+  from gradient_checker import GradientChecker, create_op
+  from op_test_util import OpTestMeta
+
+  class TestMulOp(unittest.TestCase):
+      __metaclass__ = OpTestMeta
+
+      def setUp(self):
+          self.type = "mul"
+          self.inputs = {
+              'X': np.random.random((32, 84)).astype("float32"),
+              'Y': np.random.random((84, 100)).astype("float32")
+          }
+          self.outputs = {'Out': np.dot(self.inputs['X'], self.inputs['Y'])}
+  ```
+Get its output, and compare it with the forward operator's own output.
+
+The code above first loads required packages. In addition, we have
+
+- `self.type = "mul" ` defines the type that is identical to what the operator's registered type.
+- `self.inputs` defines input, with type `numpy.array` and initializes it.
+- `self.outputs` defines output and completes the same operator computation in the Python script, and returns its result from the Python script.
+
+### Testing Backward Operators
+
+A backward operator unit test inherits `GradientChecker`, which inherits `unittest.TestCase`. As a result, **a backward operator unit test needs to be have the prefix `test_`**.
+
+```python
+class TestMulGradOp(GradientChecker):
+    def setUp(self):
+        self.op = create_op("mul")
+        self.inputs = {
+            'X': np.random.random((32, 84)).astype("float32"),
+            'Y': np.random.random((84, 100)).astype("float32")
+        }
+
+    def test_check_grad_normal(self):
+        # mul op will enlarge the relative error
+        self.check_grad(['X', 'Y'], 'Out', max_relative_error=0.5)
+
+    def test_check_grad_ingore_x(self):
+        self.check_grad(
+            ['Y'], 'Out', max_relative_error=0.5, no_grad_set=set("X"))
+
+    def test_check_grad_ingore_y(self):
+        self.check_grad(
+            ['X'], 'Out', max_relative_error=0.5, no_grad_set=set('Y'))
+```
+
+Some key points in the code above include:
+
+- `create_op("mul")` creates the backward operator's corresponding forward operator.
+- `test_normal` calls `check_grad` to validate scaling tests' correctness and stability through numeric methods.
+  - The first variable `["X", "Y"]` appoints `X` and `Y` to be scale tested.
+  - The second variable `"Out"` points to the network's final output target `Out`.
+  - The third variable `max_relative_error` points to the maximum relative tolerance error during scaling tests.
+- `test_check_grad_ingore_x` and `test_check_grad_ingore_y`branches test the cases where there is only one scaling input.
+
+### Compiling and Running
+
+
+Any new unit testing file of the format `test_*.py`  added to the director `python/paddle/v2/framework/tests` is automatically added to the project to compile.
+
+Note that **unlike the compile test for Ops, running unit tests requires compiling the entire project** and requires compiling with flag `WITH_TESTING` on i.e. `cmake paddle_dir -DWITH_TESTING=ON`.
+
+After successfully compiling the project, run the following command to run unit tests:
+
+```bash
+make test ARGS="-R test_mul_op -V"
+```
+
+Or,
+
+```bash
+ctest -R test_mul_op
+```
+
+## Remarks
+
+- Every `*_op.h` (if applicable), `*_op.cc`, and `*_op.cu` (if applicable) must be created for a unique Op. Compiling will fail if multiple operators are included per file.
+- The type with which an operator is registered needs to be identical to the Op's name. Registering `REGISTER_OP(B, ...)` in `A_op.cc` will cause unit testing failures.
+- If the operator does not implement a GPU kernel, please refrain from creating an empty `*_op.cu` file, or else unit tests will fail.
+- If multiple operators rely on some shared methods, a file NOT named `*_op.*` can be created to store them, such as `gather.h`.

doc/howto/dev/use_eigen_en.md

+## How to use Eigen in Paddle
+
+Essentially, a neural network is a compute graph. T data needed for the computation is stored in `Tensor`s and its computation procedure is described by `Operator`s. An `Operator` calls the `Compute` interface in its corresponding `OpKernel` and operates on the `Tensor`.
+
+
+### Eigen Tensor Module
+
+The Eigen Tensor module supports powerful element-wise computation. In addition, a piece of code written using it can be run on both the CPU and the GPU.
+
+Note that Eigen Tensor is still being actively developed, so its tests are not completely covered and its documentation may be sparse.
+
+For details on Eigen Tensor module, please see [doc 1](https://github.com/RLovelett/eigen/blob/master/unsupported/Eigen/CXX11/src/Tensor/README.md) and [doc 2](https://bitbucket.org/eigen/eigen/src/default/unsupported/Eigen/CXX11/src/Tensor/README.md).
+
+
+### paddle::framework::Tensor
+
+Paddle Tensor's is defined in the framework directory with the following interface:
+
+```cpp
+class Tensor {
+ public:
+  /*! Return a pointer to mutable memory block. */
+  template <typename T>
+  inline T* data();
+
+  /**
+   * @brief   Return a pointer to mutable memory block.
+   * @note    If not exist, then allocation.
+   */
+  template <typename T>
+  inline T* mutable_data(platform::Place place);
+
+  /**
+   * @brief     Return a pointer to mutable memory block.
+   *
+   * @param[in] dims    The dimensions of the memory block.
+   * @param[in] place   The place of the memory block.
+   *
+   * @note      If not exist, then allocation.
+   */
+  template <typename T>
+  inline T* mutable_data(DDim dims, platform::Place place);
+
+  /*! Resize the dimensions of the memory block. */
+  inline Tensor& Resize(const DDim& dims);
+
+  /*! Return the dimensions of the memory block. */
+  inline const DDim& dims() const;
+
+ private:
+  /*! holds the memory block if allocated. */
+  std::shared_ptr<Placeholder> holder_;
+
+  /*! points to dimensions of memory block. */
+  DDim dim_;
+};
+```
+
+`Placeholder` is used to delay memory allocation; that is, we can first define a tensor, using `Resize` to configure its shape, and then call `mutuable_data` to allocate the actual memory.
+
+```cpp
+paddle::framework::Tensor t;
+paddle::platform::CPUPlace place;
+// set size first
+t.Resize({2, 3});
+// allocate memory on CPU later
+t.mutable_data(place);
+```
+
+### paddle::framework::Tensor Usage
+`AddOp` demonstrates Tensor's usage.
+
+- InferShape
+
+When computing a neural network's compute graph, first call every `Operator`'s `InferShape` method, and use `Resize` to configure the size of the output tensor.
+
+```cpp
+void InferShape(const framework::InferShapeContext &ctx) const override {
+  PADDLE_ENFORCE_EQ(ctx.Input<Tensor>("X")->dims(),
+                    ctx.Input<Tensor>("Y")->dims(),
+                    "Two input of Add Op's dimension must be same.");
+  ctx.Output<Tensor>("Out")->Resize(ctx.Input<Tensor>("X")->dims());
+}
+```
+
+
+- Run
+
+```cpp
+void Compute(const framework::ExecutionContext& context) const override {
+  auto* input0 = context.Input<Tensor>("X");
+  auto* input1 = context.Input<Tensor>("Y");
+  auto* output = context.Output<Tensor>("Out");
+
+  output->mutable_data<T>(context.GetPlace());
+
+  auto x = EigenVector<T>::Flatten(*input0);
+  auto y = EigenVector<T>::Flatten(*input1);
+  auto z = EigenVector<T>::Flatten(*output);
+
+  auto place = context.GetEigenDevice<Place>();
+
+  z.device(place) = x + y;
+}
+```
+
+
+### paddle::framework::Tensor到EigenTensor的转换
+
+As shown above, in actual computation, we need to transform the input and output `Tensor`s into formats Eigen supports. We show some functions in [eigen.h](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/eigen.h) to implement the transformation from `paddle::framework::Tensor`to `EigenTensor/EigenMatrix/EigenVector/EigenScalar`.
+
+Using EigenTensor as an example:
+
+```cpp
+Tensor t;
+float* p = t.mutable_data<float>(make_ddim({1, 2, 3}), platform::CPUPlace());
+for (int i = 0; i < 1 * 2 * 3; i++) {
+  p[i] = static_cast<float>(i);
+}
+
+EigenTensor<float, 3>::Type et = EigenTensor<float, 3>::From(t);
+```
+
+`From` is an interfacing method provided by the EigenTensor template, which implements the transformation from a `paddle::framework::Tensor` object to an EigenTensor. Since `rank` is a template parameter, it needs to be explicitly specified at the time of the transformation.
+
+In Eigen, tensors with different ranks are different types, with `Vector` bring a rank-1 instance. Note that `EigenVector<T>::From` uses a transformation from an 1-dimensional Paddle tensor to a 1-dimensional Eigen tensor while `EigenVector<T>::Flatten` reshapes a paddle tensor and flattens it into a 1-dimensional Eigen tensor. Both resulting tensors are still typed EigenVector.
+
+For more transformations, see the [unit tests](https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/framework/eigen_test.cc) in the `eigen_test.cc` file.
+
+
+
+### Implementing Computation
+
+While computing, the device interface is needed from the EigenTensors on the left hand side of the assignments. Note that the computation between EigenTensors only changes the data originally inthe Tensor and does not change all the shape information associated with the Tensor.
+
+```cpp
+auto x = EigenVector<T>::Flatten(*input0);
+auto y = EigenVector<T>::Flatten(*input1);
+auto z = EigenVector<T>::Flatten(*output);
+auto place = context.GetEigenDevice<Place>();
+z.device(place) = x + y;
+```
+
+In this code segment, input0/input1/output can be Tensors of arbitrary dimension. We are calling Flatten from EigenVector, transforming a tensor of any dimension into a 1-dimensional EigenVector. After completing computation, input0/input1/output will retain the same shape information, and they can be resized using the `Resize` interface.
+
+Because the Eigen Tensor module is under-documented, please refer to `OpKernel`'s computation code in TensorFlow's [kernel module documentation](https://github.com/tensorflow/tensorflow/tree/master/tensorflow/core/kernels).

doc/tutorials/image_classification/index_cn.md

-图像分类教程
-==========
-
-在本教程中，我们将使用CIFAR-10数据集训练一个卷积神经网络，并使用这个神经网络来对图片进行分类。如下图所示，卷积神经网络可以辨识图片中的主体，并给出分类结果。
-<center>![Image Classification](./image_classification.png)</center>
-
-## 数据准备
-首先下载CIFAR-10数据集。下面是CIFAR-10数据集的官方网址：
-
-<https://www.cs.toronto.edu/~kriz/cifar.html>
-
-我们准备了一个脚本，可以用于从官方网站上下载CIFAR-10数据集，转为jpeg文件并存入特定的目录。使用这个脚本前请确认已经安装了pillow及相关依赖模块。可以参照下面的命令进行安装：
-
-1. 安装pillow
-
-```bash
-sudo apt-get install libjpeg-dev
-pip install pillow
-```
-
-2. 下载数据集
-
-```bash
-cd demo/image_classification/data/
-sh download_cifar.sh
-```
-
-CIFAR-10数据集包含60000张32x32的彩色图片。图片分为10类，每个类包含6000张。其中50000张图片作为训练集，10000张作为测试集。
-
-下图展示了所有的图片类别，每个类别中随机抽取了10张图片。
-<center>![Image Classification](./cifar.png)</center>
-
-脚本运行完成后，我们应当会得到一个名为cifar-out的文件夹，其下子文件夹的结构如下
-
-
-```
-train
----airplane
----automobile
----bird
----cat
----deer
----dog
----frog
----horse
----ship
----truck
-test
----airplane
----automobile
----bird
----cat
----deer
----dog
----frog
----horse
----ship
----truck
-```
-
-cifar-out下包含`train`和`test`两个文件夹，其中分别包含了CIFAR-10中的训练集和测试集。这两个文件夹下各自有10个子文件夹，每个子文件夹下存储相应分类的图片。将图片按照上述结构存储好之后，我们就可以着手对分类模型进行训练了。
-
-## 预处理
-数据下载之后，还需要进行预处理，将数据转换为Paddle的格式。我们可以通过如下命令进行预处理工作：
-
-```
-cd demo/image_classification/
-sh preprocess.sh
-```
-
-其中`preprocess.sh` 调用 `./demo/image_classification/preprocess.py` 对图片进行预处理
-```sh
-export PYTHONPATH=$PYTHONPATH:../../
-data_dir=./data/cifar-out
-python preprocess.py -i $data_dir -s 32 -c 1
-```
-
-`./demo/image_classification/preprocess.py` 使用如下参数：
-
-- `-i` 或 `--input` 给出输入数据所在路径；
-- `-s` 或 `--size` 给出图片尺寸；
-- `-c` 或 `--color` 标示图片是彩色图或灰度图
-
-## 模型训练
-在开始训练之前，我们需要先创建一个模型配置文件。下面我们给出了一个配置示例。**注意**，这里的列出的和`vgg_16_cifar.py`文件稍有差别，因为该文件可适用于预测。
-
-```python
-from paddle.trainer_config_helpers import *
-data_dir='data/cifar-out/batches/'
-meta_path=data_dir+'batches.meta'
-args = {'meta':meta_path, 'mean_img_size': 32,
-        'img_size': 32, 'num_classes': 10,
-        'use_jpeg': 1, 'color': "color"}
-define_py_data_sources2(train_list=data_dir+"train.list",
-                        test_list=data_dir+'test.list',
-                        module='image_provider',
-                        obj='processData',
-                        args=args)
-settings(
-    batch_size = 128,
-    learning_rate = 0.1 / 128.0,
-    learning_method = MomentumOptimizer(0.9),
-    regularization = L2Regularization(0.0005 * 128))
-
-img = data_layer(name='image', size=3*32*32)
-lbl = data_layer(name="label", size=10)
-# small_vgg is predined in trainer_config_helpers.network
-predict = small_vgg(input_image=img, num_channels=3)
-outputs(classification_cost(input=predict, label=lbl))
-```
-
-在第一行中我们载入用于定义网络的函数。
-```python
-from paddle.trainer_config_helpers import *
-```
-
-之后定义的`define_py_data_sources2`使用Python数据提供器，其中 `args`将在`image_provider.py`进行使用，该文件负责产生图片数据并传递给Paddle系统
- - `meta`: 训练集平均值。
- - `mean_img_size`: 平均特征图的高度及宽度。
- - `img_size`：输入图片的高度及宽度。
- - `num_classes`：类别个数。
- - `use_jpeg`：处理过程中数据存储格式。
- - `color`：标示是否为彩色图片。
- 
- `settings`用于设置训练算法。在下面的例子中，learning rate被设置为0.1除以batch size，而weight decay则为0.0005乘以batch size。
- 
- ```python
-settings(
-    batch_size = 128,
-    learning_rate = 0.1 / 128.0,
-    learning_method = MomentumOptimizer(0.9),
-    regularization = L2Regularization(0.0005 * 128)
-)
-```
-
-`small_vgg`定义了网络结构。这里我们使用的是一个小的VGG网络。关于VGG卷积神经网络的描述可以参考：[http://www.robots.ox.ac.uk/~vgg/research/very_deep/](http://www.robots.ox.ac.uk/~vgg/research/very_deep/)。
-```python
-# small_vgg is predined in trainer_config_helpers.network
-predict = small_vgg(input_image=img, num_channels=3)
-```
-配置创建完毕后，可以运行脚本train.sh来训练模型。
-
-```bash
-config=vgg_16_cifar.py
-output=./cifar_vgg_model
-log=train.log
-
-paddle train \
---config=$config \
---dot_period=10 \
---log_period=100 \
---test_all_data_in_one_period=1 \
---use_gpu=1 \
---save_dir=$output \
-2>&1 | tee $log
-
-python -m paddle.utils.plotcurve -i $log > plot.png
-```
-- 这里我们使用的是GPU模式进行训练。如果你没有GPU环境，可以设置`use_gpu=0`。
-- `./demo/image_classification/vgg_16_cifar.py`是网络和数据配置文件。各项参数的详细说明可以在命令行参数相关文档中找到。
-- 脚本`plotcurve.py`依赖于python的`matplotlib`模块。因此如果这个脚本运行失败，也许是因为需要安装`matplotlib`。
-在训练完成后，训练及测试误差曲线图会被`plotcurve.py`脚本保存在 `plot.png`中。下面是一个误差曲线图的示例：
-
-<center>![Training and testing curves.](./plot.png)</center>
-
-## 预测
-在训练完成后，模型及参数会被保存在路径`./cifar_vgg_model/pass-%05d`下。例如第300个pass的模型会被保存在`./cifar_vgg_model/pass-00299`。
-
-要对一个图片的进行分类预测，我们可以使用`predict.sh`，该脚本将输出预测分类的标签：
-
-```
-sh predict.sh
-```
-
-predict.sh:
-```
-model=cifar_vgg_model/pass-00299/
-image=data/cifar-out/test/airplane/seaplane_s_000978.png
-use_gpu=1
-python prediction.py $model $image $use_gpu
-```
-
-## 练习
-在CUB-200数据集上使用VGG模型训练一个鸟类图片分类模型。相关的鸟类数据集可以从如下地址下载，其中包含了200种鸟类的照片（主要来自北美洲）。
-
-<http://www.vision.caltech.edu/visipedia/CUB-200.html>
-
-
-
-
-## 细节探究
-### 卷积神经网络
-卷积神经网络是一种使用卷积层的前向神经网络，很适合构建用于理解图片内容的模型。一个典型的神经网络如下图所示：
-
-![Convolutional Neural Network](./lenet.png)
-
-一个卷积神经网络包含如下层：
-
-- 卷积层：通过卷积操作从图片或特征图中提取特征
-- 池化层：使用max-pooling对特征图下采样
-- 全连接层：使输入层到隐藏层的神经元是全部连接的。
-
-卷积神经网络在图片分类上有着惊人的性能，这是因为它发掘出了图片的两类重要信息：局部关联性质和空间不变性质。通过交替使用卷积和池化处理， 卷积神经网络能够很好的表示这两类信息。
-
-关于如何定义网络中的层，以及如何在层之间进行连接，请参考Layer文档。

doc/tutorials/image_classification/index_en.md

-Image Classification Tutorial
-==============================
-
-This tutorial will guide you through training a convolutional neural network to classify objects using the CIFAR-10 image classification dataset.
-As shown in the following figure, the convolutional neural network can recognize the main object in images, and output the classification result.
-
-<center>![Image Classification](./image_classification.png)</center>
-
-## Data Preparation
-First, download CIFAR-10 dataset. CIFAR-10 dataset can be downloaded from its official website.
-
-<https://www.cs.toronto.edu/~kriz/cifar.html>
-
-We have prepared a script to download and process CIFAR-10 dataset. The script will download CIFAR-10 dataset from the official dataset.
-It will convert it to jpeg images and organize them into a directory with the required structure for the tutorial. Make sure that you have installed pillow and its dependents.
-Consider the following commands:
-
-1. install pillow dependents
-
-```bash
-sudo apt-get install libjpeg-dev
-pip install pillow
-```
-
-2. download data and preparation
-
-```bash
-cd demo/image_classification/data/
-sh download_cifar.sh
-```
-
-The CIFAR-10 dataset consists of 60000 32x32 color images in 10 classes, with 6000 images per class. There are 50000 training images and 10000 test images.
-
-Here are the classes in the dataset, as well as 10 random images from each:
-<center>![Image Classification](./cifar.png)</center>
-
-
-After downloading and converting, we should find a directory (cifar-out) containing the dataset in the following format:
-
-```
-train
----airplane
----automobile
----bird
----cat
----deer
----dog
----frog
----horse
----ship
----truck
-test
----airplane
----automobile
----bird
----cat
----deer
----dog
----frog
----horse
----ship
----truck
-```
-
-It has two directories:`train` and `test`. These two directories contain training data and testing data of CIFAR-10, respectively. Each of these two folders contains 10 sub-folders, ranging from `airplane` to `truck`. Each sub-folder contains images with the corresponding label. After the images are organized into this structure, we are ready to train an image classification model.
-
-## Preprocess
-After the data has been downloaded, it needs to be pre-processed into the Paddle format. We can run the following command for preprocessing.
-
-```
-cd demo/image_classification/
-sh preprocess.sh
-```
-
-`preprocess.sh` calls `./demo/image_classification/preprocess.py` to preprocess image data.
-```sh
-export PYTHONPATH=$PYTHONPATH:../../
-data_dir=./data/cifar-out
-python preprocess.py -i $data_dir -s 32 -c 1
-```
-
-`./demo/image_classification/preprocess.py` has the following arguments
-
-- `-i` or `--input` specifes  the input data directory.
-- `-s` or `--size` specifies the processed size of images.
-- `-c` or `--color` specifes whether images are color images or gray images.
-
-
-## Model Training
-We need to create a model config file before training the model. An example of the config file (vgg_16_cifar.py) is listed below. **Note**, it is slightly different from the `vgg_16_cifar.py` which also applies to the prediction.
-
-```python
-from paddle.trainer_config_helpers import *
-data_dir='data/cifar-out/batches/'
-meta_path=data_dir+'batches.meta'
-args = {'meta':meta_path, 'mean_img_size': 32,
-        'img_size': 32, 'num_classes': 10,
-        'use_jpeg': 1, 'color': "color"}
-define_py_data_sources2(train_list=data_dir+"train.list",
-                        test_list=data_dir+'test.list',
-                        module='image_provider',
-                        obj='processData',
-                        args=args)
-settings(
-    batch_size = 128,
-    learning_rate = 0.1 / 128.0,
-    learning_method = MomentumOptimizer(0.9),
-    regularization = L2Regularization(0.0005 * 128))
-
-img = data_layer(name='image', size=3*32*32)
-lbl = data_layer(name="label", size=10)
-# small_vgg is predined in trainer_config_helpers.network
-predict = small_vgg(input_image=img, num_channels=3)
-outputs(classification_cost(input=predict, label=lbl))
-```
-
-The first line imports python functions for defining networks.
-```python
-from paddle.trainer_config_helpers import *
-```
-
-Then define an `define_py_data_sources2` which use python data provider
-interface. The arguments in `args` are used in `image_provider.py` which
-yeilds image data and transform them to Paddle.
- - `meta`: the mean value of training set.
- - `mean_img_size`: the size of mean feature map.
- - `img_size`: the height and width of input image.
- - `num_classes`: the number of classes.
- - `use_jpeg`: the data storage type when preprocessing.
- - `color`: specify color image.
-
-`settings` specifies the training algorithm. In the following example,
-it specifies learning rate as 0.1, but divided by batch size, and the weight decay
-is 0.0005 and multiplied by batch size.
-```python
-settings(
-    batch_size = 128,
-    learning_rate = 0.1 / 128.0,
-    learning_method = MomentumOptimizer(0.9),
-    regularization = L2Regularization(0.0005 * 128)
-)
-```
-
-The `small_vgg` specifies the network. We use a small version of VGG convolutional network as our network
-for classification. A description of VGG network can be found here [http://www.robots.ox.ac.uk/~vgg/research/very_deep/](http://www.robots.ox.ac.uk/~vgg/research/very_deep/).
-```python
-# small_vgg is predined in trainer_config_helpers.network
-predict = small_vgg(input_image=img, num_channels=3)
-```
-After writing the config, we can train the model by running the script train.sh.
-
-```bash
-config=vgg_16_cifar.py
-output=./cifar_vgg_model
-log=train.log
-
-paddle train \
---config=$config \
---dot_period=10 \
---log_period=100 \
---test_all_data_in_one_period=1 \
---use_gpu=1 \
---save_dir=$output \
-2>&1 | tee $log
-
-python -m paddle.utils.plotcurve -i $log > plot.png
-```
-
-- Here we use GPU mode to train. If you have no gpu environment, just set `use_gpu=0`.
-
-- `./demo/image_classification/vgg_16_cifar.py` is the network and data configuration file. The meaning of the other flags can be found in the documentation of the command line flags.
-
-- The script `plotcurve.py` requires the python module of `matplotlib`, so if it fails, maybe you need to install `matplotlib`.
-
-
-After training finishes, the training and testing error curves will be saved to `plot.png` using `plotcurve.py` script. An example of the plot is shown below:
-
-<center>![Training and testing curves.](./plot.png)</center>
-
-
-## Prediction
-After we train the model, the model file as well as the model parameters are stored in path `./cifar_vgg_model/pass-%05d`. For example, the model of the 300-th pass is stored at `./cifar_vgg_model/pass-00299`.
-
-To make a prediction for an image, one can run `predict.sh` as follows. The script will output the label of the classfiication.
-
-```
-sh predict.sh
-```
-
-predict.sh:
-```
-model=cifar_vgg_model/pass-00299/
-image=data/cifar-out/test/airplane/seaplane_s_000978.png
-use_gpu=1
-python prediction.py $model $image $use_gpu
-```
-
-## Exercise
-Train a image classification of birds using VGG model and CUB-200 dataset. The birds dataset can be downloaded here. It contains an image dataset with photos of 200 bird species (mostly North American).
-
-<http://www.vision.caltech.edu/visipedia/CUB-200.html>
-
-
-
-
-## Delve into Details
-### Convolutional Neural Network
-A Convolutional Neural Network is a feedforward neural network that uses convolution layers. It is very suitable for building neural networks that process and understand images. A standard convolutional neural network is shown below:
-
-![Convolutional Neural Network](./lenet.png)
-
-Convolutional Neural Network contains the following layers:
-
-- Convolutional layer: It uses convolution operation to extract features from an image or a feature map.
-- Pooling layer: It uses max-pooling to downsample feature maps.
-- Fully Connected layer: It uses fully connected connections to transform features.
-
-Convolutional Neural Network achieves amazing performance for image classification because it exploits two important characteristics of images: *local correlation* and *spatial invariance*. By iteratively applying convolution and max-pooing operations, convolutional neural network can well represent these two characteristics of images.
-
-
-For more details of how to define layers and their connections, please refer to the documentation of layers.

doc/tutorials/index_cn.md

-# 完整教程
-
-* [快速入门](quick_start/index_cn.rst)
-* [个性化推荐](rec/ml_regression_cn.rst)
-* [图像分类](image_classification/index_cn.md)
-* [情感分析](sentiment_analysis/index_cn.md)
-* [语义角色标注](semantic_role_labeling/index_cn.md)
-* [机器翻译](text_generation/index_cn.md)
-
-## 常用模型
-
-* [ResNet模型](imagenet_model/resnet_model_cn.md)
-* [词向量模型](embedding_model/index_cn.md)

doc/tutorials/index_en.md

-# TUTORIALS
-There are several examples and demos here.
-
-* [Quick Start](quick_start/index_en.md)
-* [MovieLens Regression](rec/ml_regression_en.rst)
-* [Image Classification](image_classification/index_en.md)
-* [Sentiment Analysis](sentiment_analysis/index_en.md)
-* [Semantic Role Labeling](semantic_role_labeling/index_en.md)
-* [Text Generation](text_generation/index_en.md)
-* [Image Auto-Generation](gan/index_en.md)
-
-## Model Zoo
-* [ImageNet: ResNet](imagenet_model/resnet_model_en.md)
-* [Embedding: Chinese Word](embedding_model/index_en.md)