* test=develop
The scatter op has a calc bug when the indices has same index, the scatter op use overwrite mode to calculate the same index, fix this bug by using the accumulate mode to calculate the same index.At the same time, the gather op has the same bug when the op calc the grad. And we use the lib of open-blas and eigen to optimize the time cost in accumulate mode.

* test=develop
Fix some code format problem, and the same time add the test case in gather and scatter op

* Cherry-pick fix random Python3 CI failure.

In some tests, SWEs used "print('xxx').format('xxx')". The syntax
is only supported in Python2, not python3. However, since those
lines are related to data download, if the CI machines already have
the data, it passes CI tests. That causes random failure.

* Cherry-pick: disable CUDNN case of test_warpctc_op

Also temporary disable a unit test. The test will be fixed under high priority.

* fix im2sequence padding bug, test=develop

* fix edit_distance, test=develop

* add API.spec,test=develop

* fix logging unable. test=develop

* unset sys.stdout for stream handler. test=develop

* fix newly add basicConfig. test=develop

* fix import error. test=develop

* add shape not match doc to data layer, test=develop

* fix API.spec md5
test=develop

* add deformable psroi pooling

* test=develop

* test=develop

* test=develop
modify format

* fix bug

* test=develop run ci

* test=develop
add API.spec

* add test_layers.py

* run ci again

* test=develop
run ci again

* run ci again

* test=develop
run ci again

* test=develop
run ci again

* test=develop
run ci again

* add space between two lines

* test=develop
add space between two lines

* test=develop
add space between lines

* test=develop
modify comment in nn.py

* test=develop
add space between two lines

* test=develop
add space between two lines

* update API.spec

* run ci again

* test=develop
run ci again

* rerun ci

* test=develop
rerun ci

* change input shape

* run ci

* test=develop
run ci

* modify format of nn.py

* test=develop

* test=develop

* test=develop
update API.spec

* test=develop
fix API doc

* modify API comment

* modift API comment

* test=develop
update API.spec

* test=develop
modify comment

* test=develop
modift comment

* test=develop
modift comment

* test=develop
update API.spec

* test=develop
modify comment

* test=develop
add inference in nn.py

* test=develop
update API.spec

* test=develop
resolve confict

* test=develop
update API.spec

* add unfold op
test=develop

* fix divide bug in python3 when calculating output width and height
test=develop

* add name=None in python api, move redundant code into inline function

* try to trigger ci for this code
test=develop

* add 'UserDefinedRoleMakerNCCL' for collective mode.

* code style

* add the name UserDefinedRoleMakerNCCL to __all__

* rename to UserDefinedRoleMakerCollective

* rename to UserDefinedCollectiveRoleMaker

Add Pipeline Concurrency Train Mode:
- Cpp: pipeline_trainer & section_worker
- Python: PipelineOptimizer
- Add a new data_feed type: PrivateInstantDataFeed
- Add a test demo of pipeline trainer and the test model is gnn
- Do not support win32 now

test=develop

fix doc: conv3d, layer norm, bilineartensorproduct, conv2dtranspose, conv3dtranspose,rowconv, groupnorm, spectralnorm, treeconv

hidden api: sequenceConv

test=develop

TODO: it is a temporary fix for Paddle release 1.5. We have to fix
this failed unit test soon.

test=develop

test=develop

1. Enhence auto pruning. 
2. Fix save/load graph when using py_reader.
test=develop

* Enable seq_pool op to accept len 0 input

test=develop

* Update sequence_pool's api

test=develop

* Add more unittest cases for seq_pool op

test=develop

* Remove legacy comments

test=develop

* Don't use template in op maker

test=develop

* add api commet; test=develop

* fix fc dtype bug; test=develop

* remove float32 in default parameter; test=develop

* fix exmpale bug; test=develop

* fix build once; test=develop

* fix num_chanels bug; test=develop

* fix install check failed bug; test=develop

* fix regularizer lod bug; test=develop

* fix exception bug and one_hot expand; test=develop

* add reshape support tensor; test=develop

* fix reshape bug; test=develop

* change reshape attribute default value; test=develop

* fix reshape input name; test=develop

* fix reshape unitest; test=develop

* check dim tensor shape; test=develop

* WIP

* WIP

* test=develop, add api doc and example code for dygraph

* Add auto pruning strategy.
1. Fix compressor.
2. Enhence graph executor.
3. Add SAController
4. Add auto pruning strategy.
5. Add unitest for auto pruning strategy.
test=develop

* Init light-nas

* Add light nas.

* Some fix.
test=develop

* Fix sa controller.
test=develop

* Fix unitest of light nas.
test=develop

* Fix setup.py.in and API.spec.
test=develop

* Fix unitest.
1. Fix unitest on windows.
2. Fix package importing in tests directory.

* 1. Remove unused comments.
2. Expose eval_epoch option.
3. Remove unused function in search_agent.
4. Expose max_client_num to yaml file.
5. Move flops constraint to on_epoch_begin function
test=develop

* Fix light nas strategy.
test=develop

* Make controller server stable.
test=develop

* 1. Add try exception to compressor.
2. Remove unitest of light-nas for windows.
test=develop

* Add comments
Enhence controller
test=develop

* Fix comments.
test=develop

* test=develop, refine api

* test=develop, fix bug when error occured on save_persistable with no optimizer

* test=develop, refine waring

* test=develop, refine example code and comments

* test=develop, add dygraph_not_support and refine ocr

* test=develop, shrink name of dygraph_not_support

* add import, test=develop

* fix fill_constant

* fix deconv

* add trainable_statist for bn in dygraph

test=develop

* save optimizer related vars in dygraph

* test=develop, add optimizer save and load

* test=develop, add optimizer save and load

* test=develop, merge code and add multi-optimizer save and load

* test=develop, fix test_imperative_checkpoint

* test=develop, fix include error

* test=develop, fix include error

* test=develop, renew api spec

* test=develop, refine code

* test=develop, set default value for checkpoint

* test=develop, fix ci error

* test=develop, change API.spec and make api more readable

* test=develop, refine version and time stamp

* test=develop, add example code and refine code

* test=develop, refine doc

* test=develop, change version

* Enable ngraph layer_norm operator

test=develop

* Disable/Enable cuda, new unit-test test=develop

* Fix use_cudnn test=develop

* Fixed test_layer test, new funciton is added test=develop

* set use_cudnn by default test=develop

* refactor PR 16865

* delete mergetool files

* test=develop

* test=develop

* test=develop

* test=develop

* create dir for int8 model before call SaveOptimModel

* test=develop

* mkldnn int8 only support linux; test=develop

* refine code; test=develop

* remove comment; test=develop

* refine code; test=develop

* fix bug; test=develop

* add exception for mkldnn_post_training_strategy

* reuse int8v2 CAPI dataset; test=develop

* fix accuracy check bug; test=develop

* remove tab

* convert files to unix format

* test=develop

* reduce CI time;test=develop

* reduce CI time and refine code;test=develop

* refine comment; test=develop

* add cmake FLAGS;test=develop

* remove predict_num;test=develop

* use pyreader to read data

* add return_list to PyReader to support return value represented as list

* for debug

* test=develop, memory optimize for dygraph using shared_ptr

* test=develop, fix travis ci showed error

* test=develop, fix bug for recurrent usage of varbase

* test=develop, init varbase when it need to be Add

* test=develop, fix problem of recurrent gradient

* test=develop, add gradient test for recurrent varbase usage

fix flower-dataset unclose error

* use python api to reduce python time cost, test=develop

* fix travis ci, test=develop

* fix Py_None error,test=develop

* test=develop, refine ocr attention model

* test=develop, refine code, remove cpu only part

test=develop, refine code, remove cpu only part