* follow comments. test=develop

* Fix typo

* fix compile error. test=develop

* merge develop branch. test=develop

* Remove set_equal

* Polish code

* Delete unused functions

test=develop

* polish code. test=develop

* follow comment

* polish code.

* fix windows compile error. test=develop

* fix op handle.

* rerun ci. test=develop

* rerun ci. test=develop

* rerun macci. test=develop

* polish code. test=develop

* rewrite sort code. test=develop

* remove unused code. test=develop

* fix tests. test=develop

* fix conflict. test=develop

* follow comment. test=develop

* merge develop branch. test=develop

* fix tests. test=develop

* remove ToTypeIndex. test=develop

* rerun ci. test=develop

* test=develop

* fix tests. test=develop

* Enable ngraph tests for a ngraph engine
test=develop

* Move the test structure to other place
test=develop

* Add USE_NGRAPH flag, simple structure
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test=develop

test=develop

test=develop

test=develop

* Add psroi_pool operator.

* add l2 unit test
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* code refine
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* fix nccl dist test acc test=develop

* fix test=develop

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* random failed. rerun ci. test=develop

* windows failed. rerun ci. test=develop

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* add more log for dist test for ci test=develop

* increase deadline test=develop

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Revert "Merge pull request #14798 from PaddlePaddle/revert-14786-revert-14782-revert-14398-imperative"

This reverts commit b1d3a1c8, reversing
changes made to f1fb64b1.

fix cmake
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add unittest model containing while_op
remove unnecessary codes
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* enable test_gradient_clip in mac
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* refine test_gradient_clip
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* fix io doc
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* refine data_feeder doc
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* add nccl2 dist tests test=develop

* fix dist_base test=develop

* fix tests test=develop

* fix test on mac test=develop

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