Upgrade cuda minimum version to 7.0

CMakeLists.txt

@@ -77,12 +77,10 @@ if(NOT WITH_GPU)
     add_definitions(-DHPPL_STUB_FUNC)
     list(APPEND CMAKE_CXX_SOURCE_FILE_EXTENSIONS cu)
 else()
-    if(${CUDA_VERSION_MAJOR} GREATER 6)
-        LIST(APPEND CUDA_NVCC_FLAGS -std=c++11)
+    if(${CUDA_VERSION_MAJOR} VERSION_LESS 7)
+        message(FATAL_ERROR "Paddle need CUDA >= 7.0 to compile")
     endif()
 
-    set(CUDA_PROPAGATE_HOST_FLAGS OFF)
-
     if(NOT CUDNN_FOUND)
         message(FATAL_ERROR "Paddle need cudnn to compile")
     endif()

cmake/flags.cmake

@@ -138,8 +138,11 @@ foreach(flag ${GPU_COMMON_FLAGS})
 endforeach()
 
 
+set(CUDA_PROPAGATE_HOST_FLAGS OFF)
+
 # Release/Debug flags set by cmake. Such as -O3 -g -DNDEBUG etc.
 # So, don't set these flags here.
+LIST(APPEND CUDA_NVCC_FLAGS -std=c++11)
 LIST(APPEND CUDA_NVCC_FLAGS --use_fast_math)
 
 if(CMAKE_BUILD_TYPE  STREQUAL "Debug")

doc/getstarted/build_and_install/build_from_source.md

@@ -17,14 +17,15 @@ cd paddle
 
 To compile the source code, your computer must be equipped with the following dependencies.
 
-### Dependencies
-
 - **Compiler**: GCC >= 4.8 or Clang >= 3.3 (AppleClang >= 5.1)
 - **CMake**: version >= 2.8
 - **BLAS**: MKL, OpenBlas or ATLAS
 - **Protocol Buffers**: version >= 2.4, **Note: 3.x is not supported**
 - **Python**: only python 2.7 is supported currently
 
+**Note:** For CUDA 7.0 and CUDA 7.5, GCC 5.0 and up are not supported!
+For CUDA 8.0, GCC versions later than 5.3 are not supported!
+
 ### Options
 
 PaddlePaddle supports some build options. To enable it, first you need to install the related libraries. 
@@ -51,8 +52,8 @@ PaddlePaddle supports some build options. To enable it, first you need to instal
 </html>
 
 **Note:**
-  - The GPU version works best with Cuda Toolkit 7.5 and cuDNN v5.
-  - Other versions like Cuda Toolkit 6.5, 7.0, 8.0 and cuDNN v2, v3, v4 are also supported.
+  - The GPU version works best with Cuda Toolkit 8.0 and cuDNN v5.
+  - Other versions like Cuda Toolkit 7.0, 7.5 and cuDNN v3, v4 are also supported.
   - **To utilize cuDNN v5, Cuda Toolkit 7.5 is prerequisite and vice versa.**
 
 As a simple example, consider the following: