Optimize the concat and split cuda implementation for cases when the number of inputs/outputs is less than 5. (#17979)

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* fix save/load in Fleet
* add UT framework of Fleet

* Fix the GetExpectedKernelType of add_position_encoding_op.
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* Fix the doc of lstm_unit outputs in nn.py.
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* support avx and noavx core

* add catch and give some log

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* fix build

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* add missing package

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* fix pybind name

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* fix import error

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* conbime noavx core

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* add requirements

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* fix unkown message

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* fix api spec

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* refine and clean

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* update

* pass dist ut

* follow comments

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* refine scripts

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* 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

Repair error prompt: Users are prompted to check whether the model or parameter files are damaged when loading parameters are wrong.

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* 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 bug in sequence_unpad op, when allocate the output memory do not match actual memory, check memory failed. Fix this bug by allocating the output memeory in correct code position.

* 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
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* add deformable psroi pooling

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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
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* fix divide bug in python3 when calculating output width and height
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* add name=None in python api, move redundant code into inline function

* try to trigger ci for this code
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* add 'UserDefinedRoleMakerNCCL' for collective mode.

* code style

* add the name UserDefinedRoleMakerNCCL to __all__

* rename to UserDefinedRoleMakerCollective

* rename to UserDefinedCollectiveRoleMaker

* - removed is_reusing_

* - Added TID to keys for reusing apart from softmax PD

* - compilation fix

* - Yet another compilation fix

* - Batch Norm and Conv adapted

* - Fix to softmax MT

* - Fixes to MT code of MKL-DNN

* - Lint fixes

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* update anakin-engine interfaces for content-dnn

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* support only-gpu mode of Anakin

modify eltwise parse

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* modification for thread-safe

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* Integrated template instance

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* increase template parameters

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* support MLU predictor

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* update anakin cmake files

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* update TargetWrapper::set_device

* update the initialization of anakin subgraph

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* use the default constructor of base class

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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

fix deconv2d bug for cycle_gan

* fix: when use the load model from memory mode, the RAM occupy is high

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* ligth mem reuse
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* fix cpplint
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fix doc: conv3d, layer norm, bilineartensorproduct, conv2dtranspose, conv3dtranspose,rowconv, groupnorm, spectralnorm, treeconv

hidden api: sequenceConv

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

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fix merge conflict of 'Remove attribute in Allocator::Allocate' and elementwise_add_mkldnn_op (#17949)

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1. Enhence auto pruning. 
2. Fix save/load graph when using py_reader.
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* remove attribute in Allocator::Allocate, test=develop

* fix travis ci error, test=develop

* Enable seq_pool op to accept len 0 input

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* Update sequence_pool's api

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* Add more unittest cases for seq_pool op

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* Remove legacy comments

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* Don't use template in op maker

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This change doesn't effect CI task because CI docker config build
was done in another way.

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* 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

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* 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