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

test=develop

* 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.

test=develop

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

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

* fix API.spec md5
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* add deformable psroi pooling

* test=develop

* test=develop

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

test=develop

* ligth mem reuse
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* fix cpplint
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fix merge conflict of 'Remove attribute in Allocator::Allocate' and elementwise_add_mkldnn_op (#17949)

test=develop

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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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* 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

* fix cuda/cudnn version detection error, test=develop

* fix again, test=develop

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fix bug: the lod_tensor_to_array op will aplly a new var but not release when dong inference (#17856)

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