* 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

* fix instag op

* fix instag bug: Some tiny logical error, occurring when ins_tag (2nd input) is multiple. test=develop

* add kernel for unsqueeze_op, test=develop

* add kernel for unsqueeze_op, test=develop

* add kernel for unsqueeze_op, test=develop

* paddle::framework::vectorize() templatization

test=develop

* update pybind/imperative.cc

test=develop

* revert update on unsqueeze_op.cc and warpctc_cudnn_op.cu.cc

test=develop

fix cmakelist deps: remove unnecessary deps and add proper op deps

* remove -Wmaybe-uninitialized warning

test=develop

* remove uninitialized op_handle_ in scale_loss_grad_op_handle.cc

test=develop

test=develop

* test=develop codegen for fused elementwise operation

* fix test=develop

* delete useless raw variables in Conv2D, test=develop

* adjust the vars number in test_graph_wrapper to pass unittest, test=develop

* test=develop,  communicator merge add => merge average

* remove assert.h

* change PADDLE_ASSERT_MSG to PADDLE_ENFORCE

test=develop

* fix tensorrt paddle_enforce

test=develop

* enable inplace for affine_channel op, dropout op, test=develop

* remove dropout inplace for ngraph fails, test=develop

test=develop

elementwise broadcast function enhancement

Add user-friendly error message in optimizer ops to give a hint about the position sensitive problem of run(startup_program) (#19605)

* add extra error message hint in optimizer ops

* polish format & delete useless change, test=develop

* extract init judue from shape compare, test=develop

* add kernel for flatten_op, test=develop

* add kernel for flatten_op, test=develop

* fix the license and remove redundant code, test=develop

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

test=develop

test=develop

* using MKLDNNMemoryFormat = mkldnn::memory::format changes
test=develop

* PADDLE_ENFORCE update
test=develop

* 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

* 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

* - First set of modifications

- Compilation fixes

- compilation fix

- Another compilation fix

- Moved AcquireSoftmaxPrimitiveDescriptor call into handler

- MKL-DNN Softmax PD refactor

test=develop

- Compilation fix

test=develop

- another compilation fix

- cosmetcis

test=develop

- Compilation fix

- Fix to crash when softmax backward is created

* - Fixes after review of softmax refactoring

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

* Modify the dropout op to multi-thread
test=develop

* define parallel
test=develop

test=develop

* add topk_avg_pooling

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