elementwise broadcast function enhancement

* add kernel for flatten_op, test=develop

* add kernel for flatten_op, test=develop

* fix the license and remove redundant code, 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

* add scatter_nd op, test=document_preview test=develop

* fixed the document, test=document_preview test=develop

* modify the notes, test=document_preview test=develop

* remove the ShareDataWith, test=develop

* test=develop
Fix the scatter op bug when use the add mode, and support the int64 data type of scatter_op Index(#18804).

* test=develop
Remove the PADDLE_ENFORCE and use PADDLE_ENFORCE_EQ

* test=develop
Remove the fix bug of scatter_add, and just add the support of int64 in scatter_add

* test=develop
Add the test case for scatter op, the test case just for index int64

* add to and detach for Variable in dygraph, test=develop

* add detach for Variable in dygraph, test=develop

* add detach for Variable in dygraph, test=develop

* add detach for Variable in dygraph, test=develop

* add detach for Variable in dygraph, test=develop

* add detach for Variable in dygraph, test=develop

* add exception check, test=develop

test=develop

Disable test_boxps in win32.
Adjust filename to avoid latent multi-thread problem.

* update ngraph ops test=develop

* update unittest test=develop

* increase coverage test=develop

* remove unused PADDLE_ASSERT(_IS_NOT_ERROR)

* replace PADDLE_ASSERT with PADDLE_ASSERT_MSG

test=develop

Change backward_guard to optimize_guard to maximize the allreduce overlap

* fix batchnorm api param: data_layout

* fix batchnorm data_layout param; test=develop

test=develop, test=document_preview

* add padding in linear_chain_crf op

* modify API.spec

* add linear_chain_crf_op.cc and linear_chain_crf_op.h

* remove useless unit test , test=develop

* modify API.spec, test=develop

* remove some blanks in nn.py , test=develop

* fix some bugs on nn.py and API.spec ,test=develop

* fix nn.py, test=develop

* fix API.spec ,test=develop

* fix bug of CI test in test_linear_chain_crf_op.py

* fix bug of CI test in test_linear_chain_crf_op.py, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* remove paddle_enforce, test=develop

* modify nn.py, test=develop

* fix API.spec, test=develop

* fix unittest bug, test=develop

* 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

* fixed the code for coverage

* fixed the document,test=document_preview test=develop

- Refactor step 1

- Compilation fix

- Yet another compilation fix

- Even more compilation fix

- Lint fixes

test=develop

- Removed deprectaed PADDLE_ENFORCE occurance

test=develop

- Candidate fix to BN forward

- Lint fixes

test=develop

- Refactoring in data_layout_transform

- compilation fix

- Another comppilation fix

- Step further into darkness

- Yet another compilation fix

- Yet another compilation fix

- missing header

- compilation fix

- Added MKLDNN -> Paddle conversion in fetch op

test=develop

- Compilation fix

test=develop

- Lint

test=develop

- Mul fix

- Fix to MKLDNN MUL op and Elementwise MUL UT

test=develop

- Workaround for diffrent weights with groups representation Paddle vs
  MKL-DNN.

test=develop

- Candidate fix for 5D convolution with groups

- Refactor of fix for conv3d and conv2d in fetch op

test=develop

- Compilation fix

- Still same compilation fix

- Compilation fix

- Compilation fix

- Reverted refactoring of fixes

- Adapted test_conv2d_int8_mkldnn so it exects data in NCHW format
  not NHWC

test=develop

- minor fix in UT

test=develop

- Lint fixes

test=develop

* add topk_avg_pooling

* refine api doc and modify api.spec test=develop

* Disable GC in test_parallel_executor_se_resnext
test=develop

* add thread scope stat accurate metrics test=develop

* fix style

* fix style

* fix style

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix style test=develop

* fix conflict

* fix style

* fix style test=develop

* fix error test=develop

* fix error test=develop

Fix mean_iou api misleading example

* update executor feed

test=develop

* dump slot

* test

* proto

* dump slot

* test

* proto

* code style

* code style

* code style

* style

* add delete after unseen days

* add unseen days

* code style

* conflict solve
test=develop

* add clear model

* code style
test=develop

* code style
test=develop

* support debug tensor of each ins
test=develop

* support debug tensor of each ins
test=develop

* learning rate

* code style

* code style

* code style

* code style

* code style

* code style

* code style

* code style

* code style

* code style

* code style

* code style

* code style
test=develop

* code style
test=develop

* unitest

* style

* style

* multi phase

* add channel

* code style

* style

* style

* unitest

* style

* define

* define
test=develop

* style
test=develop

* rm define
test=develop

* linux

* linux
test=develop

* style
test=develop

* output format
test=develop

* windows ci
test=develop

fleet_desc sort fc name by dictionary sort, but we want to sort by number.

fix row_conv_op to force it support lodtensor and tensor input simultaneously, test=develop (#19412)

Support Tensor input for row_conv_op

* fix con2d transpose bias by create and init it in build_onee

* fix API spec

* test=develop, invoke ci

* fix bias_attr and act has no effect error on layer norm, conv2dTranpose, billinearTensorProduct, sequece_conv. fix original_mode not used error on GRUunit. fix sample_weight not set error on NCE. Add ut for all thoese layer

* test=develop, change success standard for conv2dTranspose

* test=develop, fix test_layers to invoke some error branch

* test=develop, fix sample code

* test=develop, fix BilinearTensorProduct failed in dygraph mode

* test=develop, fix test_layers segment fault error

test=develop

* fix correctness of the communicator

* fix a bug in send thread when sending var context is empty, test=develop

* add lookup_table_prefetch_op and prefetch optimize, test=develop

* remove remote prefetch GPU supported

* word2vec force with CPU, test=develop

* test dist remote lookup table force with CPU, test=develop

* enabel test_parallel_dygraph_se_resnext
test=develop

* supports multiple NCCL communicators preserved in NCCLCommContext
test=develop

* add ut for c_comm_init_all operator and fix cuda resource release problem
test=develop

* improve sequence_conv api doc test=develop

* add warning for padding param test=develop

modify into deprecated

fix fleet_desc dense_table unsort bug ，not  support format for abacus hotstart yet.

* support tensor input with padding for warpctc op

* merge with develop

* test=develop

* modified python API examples test=develop

* nn.py is modified for code coverage test=develop

* update documents info about warpctc op in API.spec test=develop

* add test_warpctc_with_padding in test_layers test=develop

* add warning log for cuda_version back to warpctc_op.cc

* modify API.spec for warpctc op test=develop

* modify API.spec

* update warpctc test to new CompiledProgram API test=develop

* modify code examples for warpctc op test=develop

* modify API.spec for warpctc op test=develop

* modify API.spec for warpctc op test=develop