test=develop

* add a base class for the Communicator
* add AsyncCommunicator Impl for async distributed training

test=develop

test=develop

* Add RecordHistoryLocalExecScopes
test=develop

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

* add comments to reference count members, test=develop

* fix warning info
test=develop

* fix bug of all_reduce_deps_pass
test=develop

* Open fuse all reduce op
test=develop

* Add Fuse optimization op log

* Add log in fuse_optimizer op pass and fuse all_reduce op pass

* replace with boost::optional<bool>
test=develop

* Polish code
test=develop

* fix code coverage
test=develop

TemporaryAllocator is a singleton used for allocating memory for Cudnn. Since it is a singleton, we can delete it for better performance in memory.

We replace TemporaryAllocator by CUDADeviceContextAllocator and CUDADeviceContextAllocation, which uses stream callback to delete the memory allocated for the stream to avoid singleton.

Also added data_feed_proto to operator to fix CI in CPU compilation

* fix vlog level and fuse option type
test=develop

* Enable fused_all_reduce_op_handle support GPU and CPU Gradients

* merge_empty_lod_tensor, test=develop

* fix multiclass_nms, test=develop

* refine API.spec, test=develop

* add unittest case for fetch, test=develop

* add lod tensor test, test=develop

* return index for multiclass_nms, test=develop

* add api for multiclass_nms2

* update API.spc, test=develop

* refine api doc, test=develop

* fix test_detection.py, test=develop

* polish code, test=develop

* add more unittest case, test=develop

* remove -Wmaybe-uninitialized warning

test=develop

* remove uninitialized op_handle_ in scale_loss_grad_op_handle.cc

test=develop

* enable ngraph throught build_strategy test=develop

* add unittest test=develop

* put use_ngraph unconditional test=develop

* remove paddle_enforce test=develop

* remove paddle_enforce test=develop

* fix copyright test=develop

* limit for ngraph only test=develop

* increase num_iteration_per_drop_scope
test=develop

* Fix bug of while_op
test=develop

* fix bug of whileOp
test=develop

test=develop

Polish fleet API to support cuda collective mode and nccl2 mode

* Disable fuse optimization
test=develop

* remove legacy memory optimization codes, test=develop

* follow huihuang's comments,test=develop

* follow luotao's comments, test=develop

* open fuse optimization ops
test=develop

* first version memory optimize pass, test=develop

* remove move_tensor_sharing_pass, test=develop

* refine code comments, add unittests, test=develop

* turn off memory_optimize by default, test=develop

* follow huihuang's comments, test=develop

* follow chengduoZH's comments, test=develop

* fix grammar error, add const qualifier, fix pass_test exception message, test=develop

* follow chengduoZH's comments 2nd, test=develop

* support sparse gradients
test=develop

test=develop

* 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

* clean code of dim and place, test=develop

* fix failed unittests, test=develop

* add is_runnning in communicator, test=develop

* clean build_strategy
test=develop

* DataBalanceOpHandle has been removed
test=develop

* debug

* update build_strategy.
test=develop

* fix code bug
test=develop

test=develop