* rename mkldnn set/get_cur_thread_id() to set/get_cur_mkldnn_session_id()

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* update session id definition and adjust logic for default behavior

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* reset logic in mkldnn reuse as most of cases work in default.

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1. Use CudnnWorkspaceHandle in exhaustive search of conv_cudnn.
2. For Ops using CudnnWorkspaceHandle in exhaustive search, release their GPU memory after exhaustive search.

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* speedup gc and inplace softmax_with_cross_entropy_grad
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* refine models gpu mem
Merge skip vars and warning messages of mem opt
remove relu mem opt
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* follow comments
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* wip allreduce in op

* wip

* wip

* wip

* wip adding test

* wip for conflict with mp mode

* fix tests test=develop

* fix cpu build test=develop

* fix travis clang format test=develop

* fix cpu build test=develop

* update api.spec test=develop

* delete comment test=develop

* fix cpplint test=develop

* fix test=develop

* follow comment test=develop

* add file test=develop

* fix build test=develop

* update test=develop

* to be compatible with sync_bn, and fix mp mode in develop test=develop

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* Support Sync Batch Norm.
* Note, do not enable it in one device.

Usage:

build_strategy = fluid.BuildStrategy()
build_strategy.sync_batch_norm = True
binary = fluid.compiler.CompiledProgram(tp).with_data_parallel(
        loss_name=loss_mean.name,
        build_strategy=build_strategy)

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This reverts commit 358e657f.

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This reverts commit 064512aa.

* remove workspace_handle in conv2d_cudnn
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* remove workspace_handle
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* fix bug
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* make test_conv2d_op SERIAL
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* save memory in conv_cudnn
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* enhance thread safety
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* enhance temporary allocator
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* Add excess fraction
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* follow comments
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* fix bug and code refine
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* fix memory size check
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* rename reuse_tmp_allocation_excess_fraction
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* refine tensor
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* refine tensor
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* fix device_context log
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* Add Temporal Allocator

* add Temporay Allocator to DeviceContext
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* code refine
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* fix mean_iou
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* Add DeviceTemporaryAllocator
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* fix conv_op bug
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* small fix
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* code refine
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* log refine
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* fix unit test
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* move double check

* refine concat_and_split
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* add limit_of_temporary_allocation
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* fix name
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The macro should be defined by compiler rather than by source.

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* refine cublase
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* code refine

* refine cublas

* add GEMME_EX

* add enable_cublas_tensor_op_math doc and add cublasCall
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* fix CublasCall for cuda version
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* fix error
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* fix GEMM_EX to be compatible with gcc 4.8
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* add GEMM_EX
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* to compatiable with gcc4.8
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* feat(platform): lazy initialization of devicecontext in pool

Use std::async(deferer, []{...}) to lazy initialize DeviceContext in Pool

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* Add future includes

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Make all blob info saved in global device context to be thread based.
Meanwhile save thread id in thread local storage in ParallelDo

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This reverts commit 1d91a49d.

* some trivial opt

* remove the fix of lod_tensor and shrink_rnn_memory_op

* refine ShrinkRNNMemoryOp

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This reverts commit 151e169e.