* Fix bug: add feed_vars to the prune function

* Support looking up embeddings from BoxPS.
* Add a _pull_box_sparse op, for now this op is not exposed to users.
* Add a BoxHelper class, providing 'BeginPass', 'EndPass', 'FeedPass' functions and so on.
* Add 'BoxPSDataset' in python code.
* Add a compile options WITH_BOX_PS and a MACRO PADDLE_WITH_BOX_PS.
* Add UT.
* More concrete information pls refer to: https://github.com/PaddlePaddle/Paddle/pull/18982

* fix bug of getting bool Flags from os.environ, test=develop

* add empty loss_name in CompiledProgram for inplace grad test, test=develop

* add pybind interface to get all inplace ops, test=develop

* enhance OpTest to check whether the consistency of operator when using and not using inplace, test=develop

* handle corner cases in op_test, test=develop

* support outputs without tensor holder_, like XShape in reshape_op, test=develop

* fix bug, some op has GradOpMaker, but actually no grad_op in OpInfoMap, test=develop

* use reshape_grad instead of reshape in FlattenGradOp, test=develop

* fix error debug dims info for variables like XShape, test=develop

* change computational order in sum_op to relieve computation difference using inplace, test=develop

* add inplace_atol to check group_norm, and skip inplace_grad for mkldnn, test=develop

* follow sneaxiy's comments, test=develop

* remove unused DefaultGradOpDescMaker in mkldnn op, test=develop

* fix memory overlapping of fetch var (return of executor.run), test=develop

* fix wrong usage of ParallelExecutor in op_test, test=develop

* remove useless parameter and simplify code

* avoid tensor destruct untimely, test=develop

* add testcase independent of OpTest, test=develop

* fix warpctc.dll not found issue, test=develop

* revert the linux platform change, test=develop

* delete warpctc_lib_path.h.in, test=develop

* add SetPySitePackagePath function

* fix warpctc.dylib not found issue on Mac, test=develop

* improve the paddle lib path setting logic, test=develop

* fix mac ci issue caused by test_warpctc_op unittest, test=develop

* tweak code, test=develop

* update parallel.py
test=develop

* remove legacy memory optimization codes, test=develop

* follow huihuang's comments,test=develop

* follow luotao's comments, test=develop

test=develop

* support sparse gradients
test=develop

* feature/auto_growth_allocator, test=develop

* add unittest of AlignedAllocator, test=develop

* try to turn on auto_growth to test on CI, test=develop

* fix segmentation fault in mixed_vector.h, test=develop

* add unittests, test=develop

* remove async executor and add data_feed.proto to the deps of train demo

* feature/buffer_shared_inplace, test=develop

* refine code, test=develop

* fix elementwise_add op cpu inplace and sum inplace bug, test=develop

* add unittest and debug log, test=develop

* fix parallel_executor scope bug, polish code, test=develop

* fix sum op, activation op, single_in_place_inference bug, test=develop

* remove kLocalExecScopeName, test=develop

* fix unittest,test=develop

* fix out_var first version bug, test=develop

* follow comments,test=develop

* refine cuda place error msg, test=develop

* use LOG(ERROR)+exit(-1), test=develop

* update execution_strategy option default value
test=develop

* fix doc error
test=develop

* support avx and noavx core

* add catch and give some log

test=develop

* fix build

test=develop

* add missing package

test=develop

* fix pybind name

test=develop

* fix import error

test=develop

* conbime noavx core

test=develop

* add requirements

test=develop

* fix unkown message

test=develop

* fix api spec

test=develop

* refine and clean

test=develop

* update

* pass dist ut

* follow comments

test=develop

* refine scripts

test=develop

* fix the ParallelExecutor on Windows
test=develop
* restrict to use one GPU only under windows

* fix prepare context redundant code problem, optimize executor by caching create_varaiables
test=develop

* cache sub_scope, program, var when use_program_cache=True is set

* make fetch_list runable with variables, add more unittest for use_program_cache

* add __str__ method for tensor and lodtensor to support print test=develop

add Run Prepared Ctx, fix pybind problem

Python examples of fluid.layers.io.double_buffer and some BuildStrategy's methods.

* polish_executor_and_add_ctx_cache

* Revert "Revert "Fix allocator bug""

This reverts commit 174d0d0b.

* Revert "fix travis ci"

This reverts commit 5656fa9f.

test=develop

* add inlined_vector.h, test=develop

* add inlined_vector_test,test=develop

* fix distribute doc

Async exe support communicator

test=develop

* add var grad hook test=develop

* test=develop, add gradient sort backward strategy

* test=develop, fix test by add FLAGS_cudnn_deterministic on new tests

* test=develop, fix memory leak in dygraph mode

* test=develop, fix memory leak in dygraph mode

* test=develop, polish code

* test=develop, polish code

* test=develop, polish code

* make parallel_executor support FLAGS_use_mkldnn

test=develop

* add warning when set mkldnn_enabled_op_types_ in non-mkldnn env

test=develop

* test=develop, add gradient sort backward strategy

* test=develop, fix test by add FLAGS_cudnn_deterministic on new tests

* reset drop local scope counter
test=develop

Fix the following API examples:

paddle.fluid.scope_guard
paddle.fluid.backward.append_backward
paddle.fluid.cpu_places
paddle.fluid.cuda_pinned_places
paddle.fluid.cuda_places
paddle.fluid.in_dygraph_mode
paddle.fluid.CUDAPlace
paddle.fluid.CPUPlace
paddle.fluid.CUDAPinnedPlace