* Add conv2d_grad_grad_op
* Extracte the cuDNN conv algo searching code in conv_cudnn_helper.h.
    - Now use it in conv2d_grad_grad.
    - Will simply the searching code in conv2d and conv2d_grad in next PR.
* Enhance and fix bug in unit testing of gradient_checker.
* Support to fetch empty variables，return None in Python.

* Refine elementwise kernel.

Add a simple cuda kernel if grad x and y both exist
Use 2D block cuda kernel to do broadcast.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* refine code.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* refine code.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

test=develop

* added lrn op test=develop

* Added CreateConstant method test=develop

* avoid duplicates test=develop

* remove unused FLAGS_warpctc_dir

test=develop

* remove FLAGS_warpctc_dir

test=develop

test=develop

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

test=develop

* make_conv_cudnn_ws_size_configurable, test=develop

* change std::max to std::min
test=develop

* speedup gc and inplace softmax_with_cross_entropy_grad
test=develop

* refine models gpu mem
Merge skip vars and warning messages of mem opt
remove relu mem opt
test=develop

* follow comments
test=develop

test=develop

* - Reuse of conv PD

- conv transpose pd reused

- Added PD reusing of softmax and Batch Norm

- Refactoring and removal of not needed routines of mkl-dnn ops

test=develop

- Fix to reusing conv

test=develop

- Lint fixes

test=develop

- Further lint fixes

test=develop

- Lint  fixes

test=develop

- lint fixes

test=develop

- Lint workaround

test=develop

* - Fix after review on including boost as third party header

test=develop

* - Fix after review. Name change to something more descriptive

test=develop

test=develop

test=develop
This reverts commit c38c7c56.

* link the libwbaes.so into paddle

* polish detail, test=develop

* try fix mac_pr_ci error, test=develop

* add compile option, test=develop

* fix ci error, test=develop

* ignore failed to find mac lib, test=develop

* change cdn to bj, cdn can't get the latest version

* trigger ci, test=develop

* temporary delete win32 lib linking, test=develop

* change https to http, test=develop

* turn compile option on to off

* turn compile option off to on, test=develop

* try lib compiled by gcc4.8, test=develop

* update lib version, test=develop

* link other lib, test=develop

* add setup config

* delete false, test=develop

* delete no_soname, test=develop

* recover so name set

* fix, test=develop

* adjust make config, test=develop

* remove link to wbaes, test=develop

* remove useless define, test=develop

* fix compiled
test=develop

* follow comments test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

support win32 flag in io.cc shell.cc, fix code style problem in fleet_wrapper, fix lodtensor_printer_test problem
test=develop

test=develop

* Revert "[MKL-DNN] Fix to crash of Transformer when mkldnn is to be used (#16233)"

This reverts commit 13816dd4.
Apart from enabling transformer for MKL-DNN

* Revert "- MKL-DNN pooling updated to set_prim_desc"

This reverts commit c63f6b20.

Conflicts:
	paddle/fluid/operators/mkldnn/concat_mkldnn_op.cc

* Revert "[MKL-DNN] MKL-DNN specific Tensor modification (#15429)"

test=develop

This reverts commit dec9cf53.

* - concat compilation fix

- lint

test=develop

- Lint fixes

test=develop

- Lint fixes

test=develop

- Fix Transpose MKLDNN op

test=develop

test=develop

add include headers to fix travis-ci
test=develop

test=develop

modify allocator strategy
remove changes of legacy buddy_allocator
test=develop

* 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

test=develop

test=develop