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

This reverts commit b1d3a1c8, reversing
changes made to f1fb64b1.

* Choose to turn on use_mkldnn attribute v1

* Fix mkldnn_op empty bug

* format change test=develop

* fix ci test=develop

* fix ci test and add test in dam test=develop

* add example to dam compare test test=develop

* review changes test=develop

Revert "Revert "Revert "Imperative"""

Implement the fusion of convolution 3D and bias for mkldnn

Fix eigen deallocate bug

* enable test_gradient_clip in mac
test=develop

* refine test_gradient_clip
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* fix io doc
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* refine data_feeder doc
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Revert "Revert "Imperative""

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Implement conv3d with mkldnn library

Async executor bugfix: Tensor changed to LoDTensor

support loading from memory

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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

Revert "Imperative"

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Imperative

* Refine conv_fusion_op for identity activation.
* Fix unit testing.
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add prelu cuda kernel for inference.

fix the bug for mac build. python -c error. test=develop

remove jit namespace

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fix bug in dist train on hs, test=develop

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test=develop

Add cudnn 5 support