* add sync communicator and implement

delete redundant information.

test=release/1.7 test=document_fix

* Add TopK Op Grad CPU&GPU Kernel test=develop

* Add TopK Op Grad, modify grad op maker test=develop

* Add TopK Op Grad, modify grad op maker test=develop

* Add TopK Op Grad, modify PADDLE_ENFORCE test=develop

* Add TopK Op Grad, modify PADDLE_THROW test=develop

* Add TopK Op Grad, modify unittest test=develop

* fix ngraph top k op unittest test=develop

test=release/1.7, test=develop

* update

* update test=develop

* update compile set test=develop

* update compile set test=develop

* update test=develop

* update test=develop

* update test=develop

* update compile setting test=develop

* update compile setting test=develop

* update run demo test=develop

* update test=develop

* update test=develop

* fix test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update format test=develop

* update format test=develop

* update style test=develop

* update style test=develop

* change style test=develop

* change style test=develop

* change style test=develop

* add dataset unittest test=develop

* update test=develop

* update for record test=develop

* udpate style for record test=develop

* update for record test=develop

* update for record test=develop

* update for record test=develop

* fix format test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

* update test=develop

cherry-pick #22615

* optimizer var exlcude fluid.data var. test=develop

* fix compute priority. test=develop

* cherry-pick #22555
test=release/1.7, test=develop

* cherry-pick #22621
test=release/1.7, test=develop

pretty print for communicator flag

* add deprecated for distribute transpiler, will delete it after 2.0.0, test=develop

* enhance load program state; test=develop

* optimize commet; test=develop

* split unittests in data loader test, test=release/1.7

* split unittests to different files, test=release/1.7

* remove repeat unittest, test=release/1.7

Post_training_quantization support set quant 8/16 bits 

* 1. load model from memory

2. scale is no longer added when saving inference model

test=develop

* raise ci coverage, test=develop

* supports saving weights to memory. test=develop

* raise ci coverage, test=develop

* fix PADDLE_ENFORCE messages, test=develop

* Add support for dynamic_decode(while) training. test=develop

* Fix assign_op and tensor_array_read_write_op after solving conflict. test=develop

* Fix test_rnn_decode_api.py. test=develop

* Refine docs for apis in rnn.py. test=develop

* Adjust outputs of dynamic_decode. test=develop

* Remove the force_cpu update in assign_op. test=develop

* Remove the force_cpu update in assign_op. test=develop

* Make RNNCell.get_initial_states support batch_dim_idx argument. test=develop

* Rename _create_array_outof_while as _create_array_out_of_while in rnn.py.

test=release/1.7

* add thread barrier for the compiled program

* Introduce Ernie NLP

* Fix error regarding incorrect attr type

test=release/1.7
Co-authored-by: NWojciech Uss <wojciech.uss@intel.com>

This PR makes assign op support LoDTensorArray and enable the loop_vars in
while_loop to support tuple or list.

* Add weight quantization in post_training_quanzitaion (#22445)

* [cherry-pick]Support int16 for Tensor (#22423)

* add int16 support, test=develop, test=release/1.7
Co-authored-by: NLeo Chen <chenqiuliang@baidu.com>

[cherry-pick] #22384 and #22371

22384增加了WITH_NCCL开关

22371修改了fluid依赖lite的commit id

* add GeneralRoleMaker which is for general usage
* test=develop

* Fix GEO-SGD init & send Bug (#22375)

* test=develop, fix geo Send & Init

* test=release/1.7,test=develop, cherry-pick 8f36c395

* fix copy table bug (#22432)

* fix copy table bug of lost some feasign
* test=develop

* add hdfs ls retry time and sleep time, fix save inference (#22433)

* add hdfs ls retry time and sleep time, fix save inference
* test=develop

* fix chain doc, test=develop, test=document_preview

* fix bug with half communicator

test=release/1.7, test=develop

* add half_async in the communicator
* fix DistributedStrategy

* add multiprocess for dygraph data loader, test=develop

* polish code & add safe gurad, test=develop

* refactor dygraph dataloader & add signal handler, test=develop

* fix member initializer compile error on ci, test=develop

* fix member initializer compile error one more, test=develop

* remove useless config, test=develop

* skip windows incompatible problem, test=develop

* add unittest for coverage, test=coverage

* add more exception unittest case, test=develop

* deal with signal handler coverage, test=develop

* polish code & add signal handler tests, test=develop

* deal with coverage ci problem, test=develop

* split data loader test & coverage ci fix, test=develop

* remove test_imperative_data_loader_with_exception, test=develop

* remove singal process except test case, test=develop

* add exception tests again & remove sample list test, test=develop

* split normal and exception unittests to diff class, test=develop

* polish doc for use_multiprocess effect in static mode, test=develop

* cherry-pick fix dataloader early reset bug, test=release/1.7

* cherry-pick implementation changing, test=release/1.7

* fix ut, test=release/1.7

test=release/1.7, test=develop

* add learning rate api; test=develop

* fix uni test converage; test=develop

* fix travis ci error; test=develop

* fix comment; test=develop

* fix example error; test=develop

* polish the api description, test=develop
Co-authored-by: Nzhongpu <2013000149@qq.com>
Co-authored-by: Nhong <43953930+phlrain@users.noreply.github.com>