* add fake init for the trainer, fix large memory hold in the trainer
* do not merge recv vars from a remote endpoint, test=develop
* add recv and save op, merge slice var in one op, save memory
* remove hsigmoid with pull sparse, test=develop

* use system allocator in unittests, test=develop

* fix op bugs, test=develop

* fix tensor copy bug when src and dst are the same, test=develop

* support dlpack to tensor and implement python interface test=develop

* add unittest for _to_dlpack and from_dlpack test=develop

test=develop

Use CUDAPinnedPlace in buffered_reader

* add __str__ method for tensor and lodtensor to support print 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

* - Fix to crash of Transformer when mkldnn is to be used

Desc: TensorCopy was not setting MKLDNN primitive descriptor when layout was to be kMKLDNN

test=develop

* - Enable transformer for mkl-dnn

test=develo

* - Compilation fix

test=develop

* - Removed manual selection of MKL-DNN ops to be used in Transformer test

test=develop

* Revert "Revert "Add Event for TensorCopy" (#16022)"

This reverts commit e2da3a5b.

* use default stream
test=develop

* Revert "Add Event for TensorCopy (#15953)"

This reverts commit 7235fd66.
test=develop

* fix CI
test=develop

Add Event for TensorCopy 

* Revert "Add Event for TensorCopy (#15953)"

This reverts commit 7235fd66.
test=develop

* fix CI
test=develop

Add Event for TensorCopy 

test=develop

test=develop

test=develop

Fix code to support cpplint syntax check

test=develop

* enable pyreader use pin memory

* add py reader pin memory test test=develop

test=develop

test=develop

* "avoid copy back to cpu"

* "add infinity support"

* "fix ci"

* "add cpu macro"

* rerun ci; test=develop

* "fix api"
test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* remove template operator

* "fix compile"

* "fix ci"

* "fix ci"

* Fix tensorcopy bug

* follow comment

* Refine TensorCopy