* add parallel graph dist test=develop

* update test=develop

* update style test=develop

* Enable INT8 ReQuantize OP
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* Clean code
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* Add comments
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* Revert "Clean code"
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This reverts commit a7a49b8a.

* Modify requantize op test
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* fix requantize UT by moving public function to public test file.
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* Fix test fail due to file address change.
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* Change file address for requantize op.
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* test=develop, reconstruct layer helper to fit imperative usage

* test=develop, fix import error on py35

* test=develop, fix rnn gradient error

* test=develop, delete test use code

* test=develop, remove helper from imperative usage

* test=develop, fix test_base_layer using new helper

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, fix bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix bug

* test=develop, polish code

* add ir memory optimize test case for IfElse op, test=develop

* fix some unitttest failure by force using the python memory_optimize, test=develop

* tweak comments, test=develop

* fix unittest, test=develop

* fix unittest, test=develop

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* MKLDNN: Add UT for conv_transpose_mkldnn op.
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* MKLDNN: Add fuse_bias check UT for conv_transpose_mkldnn op.
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* staged.

* polish code

* polish code. test=develop

* polish code. test=develop

* api change. test=develop

* fix default value. test=develop

* fix default value. test=develop

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* add alloc_continuous_space_op
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* Polish code
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* follow comment
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