* rpc retry for asycsend/get/prefetch

* test=develop, change retry vlog level to 3

* test=develop, set default grpc_retry_times is 3

* support_dispensable_student_loss, test=develop

* add distillation test, test=develop

* fix distillation test non convergence problem, test=develop

* fix test_distillation fail problem, test=develop

* update elementwise double grad to save gpu memory, test=develop

* update elementwise_mul/div_grad_grad to save memory, test=develop

* remove eval function in eigen statement to save memory, test=develop

* add unittest for elementwise_div_grad_grad without dout, test=develop

* add unittest for elementwise_add_grad_grad without ddx, test=develop

* add float16 cuda kernel for elementwise double grad op, test=develop

* fix memory reuse bug on feeding variables, test=develop

* add comments to reference count members, test=develop

test=develop

zerocopytensor support uint8, analysis config support profile, analysis predictor support GetInputTensorShape, test=develop (#19822)

* add deformable conv v1 op, test=develop

* rm return in vfork

* rm return in vfork
test=develop

* Add fp16 support for dygraph
test=develop

* Add unit test
test=develop

test=develop

* update OpTest to support double grad inplace check, test=develop

* keep consistency of _calc_output function, test=develop

* fix libps.so path problem of  1/2/3 dir and third_party
* test = develop

improve pow op according to reviews:
1. Delete unnecessary judgement statements in PowGradOpDescMaker;
2. Improve test of test_api;

overload GetKernelTypeForVar

add stop_gradient=True when attr(factor) is tensor Variable, change examples in API pow.
test=develop,test=document_preview

add support parameter inference when argument shape is a list containing integer and tensor variable;
test=develop

fix reshape op according to reviews:
1. improve or message;
2. improve test of test_api.
test=develop,test=document_preview

fix reshape op: Add error message in nn.py, test=develop

add stop_gradient=True when attr(shape) is tensor Variable.
change examples in API reshape.
test=develop,test=document_preview

add support parameter inference when arguments starts or ends is a list containing integer and tensor variable;
test=develop,test=document_preview

improve slice op according to review(from hongyu). test=develop

fix slice op according to review: infer_flags, test=develop

fix slice op: improve overload operator __getitem__ to support attrs(starts and ends) are Variable.
test=develop,test=document_preview

fix test_slice_op: add TestSliceOp_decs_dim_6 to resolve conflict with test_slice_ngraph_op. test=develop

add stop_gradient=True when attr(starts) or attr(ends) is tensor Variable.
test=develop,test=document_preview

1. add tensor support for argument expand_times in expand op;
2. add support parameter inference when argument expand_times is a list containing integer and tensor variable;

improve expand op according to reviews:
1. add doc of ExpandTimes in expand_op.cc;
2. improve the test of test_api.

add stop_gradient=True when attr(expand_times) is tensor Variable, change code examples.
test=develop,test=document_preview

* support preload thread
* sleep before fleet wrapper exit for pslib core dump
* optimize hdfs log
* fix master+patch bug

* refactor dygraph,test=develop

* fix failed unittest,test=develop

* polish code,test=develop

* check windows ci error,test=develop
try to fix windows ci error by np.allclose,test=develop

* polish vlog and profiler, test=develop

* try to fix preceding ops order,test=develop

* test transformer in windows ci, test=develop

* use python c-api to speed up tracer.trace,test=develop

* test=develop, fix docker with paddle nccl problem

* test=develop, add ut for debug string and gradient_accumulator

* test=develop, add tests for layer/gradient_accumulator/prepared_op

* test=develop, fix complie error for test_prepared_op

* test=develop, add more ut for dygraph

* test=develop, create API.spec for dygraph api change

* add transform_data to dygraph

* test=develop, refoctor name to make it easier to understand

* test=develop, refoctor name to make it easier to understand

* add test and change input to const ref for safety

* test=develop, fix multi-gpu failed problem , add Tracer tests, change PADDLEENFORCE to PADDLEENFORCE_EQ

* add ut for data transform

* refine ut for data_transform

* test=develop, fix ut failed on parallel se-resnext

* test=develop, change one more PADDLE_ENFORCE

* add test_tracer on multiple devices

* test=develop, change place to mutable for data transform

* test=develop, add transform data on same place test and remove useless log

* test=develop, Add to do for data layout and and ut for conv2d with no bias

* cpu conv_grad_grad

* Implement the operator with sprase matrix multiply

* Update the URL of mklml library.

test=develop

* Disable MKLML implematation when using no-linux.

test=develop

* optimize bp with mkl sparse matrix
test=develop

* tmp add fused_emb_seq layer

* Add the support of padding_idx attribute.

test=develop

* add padding_idx support
test=develop

* implement grad refer lego
test=develop

* fix example error
test=develop

* Remove set_desc
test=develop

* fix warning info
test=develop

* fix bug of all_reduce_deps_pass
test=develop

* add unit test for square error cost op

* Refine the codes related to fc op.

* Add GPU implementation for fc functor.

* Apply fc_fuse_pass in GPU inference.
test=develop

* Change the cmake for fc op.

* Change PADDLE_ENFORCE to PADDLE_ENFORCE_EQ.

* Add an attribute to set the activation type in fc_op.

* Enhance the unittest of fc_op.
test=develop

* Remove the declaration of FCOpGrad back to the header file.
test=develop

* Set default value for newly added arguments in test_fc_op.
test=develop

* Enhance fc_fuse_pass to enable fusing relu.

* Allow print the shapes of var_desc in graph.
test=develop

* Enhance fc_fuse_pass_tester.

* Remove the use of PADDLE_ENFORCE.
test=develop

* Correct the number of ops after fusing.
test=develop

* Fix a typo.
test=develop

* Set activation_type to null when there is no relu in fc.
test=develop

* Refine fc_fuse_pass's codes.

* Enable the set of shape for tensor.

* Refine repeated_fc_relu_pass and add unittest.
test=develop

* add kernel for squeeze_op, test=develop

* delete comment, test=develop

* add kernel for unstack_op, test=develop

* add kernel for unstack_op, test=develop

* add kernel for unstack_op, test=develop

* adjust the code format, test=develop

* modify some comment, test=develop