* Init mixed precision training interface

* Add fp16 test script

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* All initializers support float16

test=develop

* Code cleanup & add more code annotations

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* Update API spec

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* Add usage example in doc

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* implement distributed transpiler with fleet

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This reverts commit c38c7c56.

* link the libwbaes.so into paddle

* polish detail, test=develop

* try fix mac_pr_ci error, test=develop

* add compile option, test=develop

* fix ci error, test=develop

* ignore failed to find mac lib, test=develop

* change cdn to bj, cdn can't get the latest version

* trigger ci, test=develop

* temporary delete win32 lib linking, test=develop

* change https to http, test=develop

* turn compile option on to off

* turn compile option off to on, test=develop

* try lib compiled by gcc4.8, test=develop

* update lib version, test=develop

* link other lib, test=develop

* add setup config

* delete false, test=develop

* delete no_soname, test=develop

* recover so name set

* fix, test=develop

* adjust make config, test=develop

* remove link to wbaes, test=develop

* remove useless define, test=develop

* Add DecoupledWeightDecay

* Add fsp operator.
1 Add unitest.
2. Add python API.
3. Add layer test.

* Add quantization strategy.
1. Add API.
2. Add unitest.

* Add distillatoin strategy.

* Add unitest config file for quantization

* Fix Copyright
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* Fix setup.py

* Fix document of layers.py.
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* Fix unitest in python3.
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* Fix documents.
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* 1. refine fsp op by batched gemm
2. remove unused import
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* Fix test_dist_se_resnext.
1. disable test distillation.
2. reset framework.py
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* Enable unitest of distillation after fixing Block._clone_variable
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* Fix cdn issue.
test=develop

* add launch mp distributed mode module test=develop

* delete unused file test=develop

* refine usage test=develop

* refine usage test=develop

* move distributed package test=develop

* add to whl package test=develop

* Add INT8 calibration support in Paddle package; test=develop

test=develop

* Init slim.

* Remove distillation demo.

* Fix import errors.
test=develop

* Fix some issues.
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* Fix configs.
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* Modify API.spec.
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* Fix format.
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* Fix format.
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* Add some comments.

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test=develop

* fix utils config, test=develop

* reweite tools in lookup table utils, test=develop

* merge develop, test=develop

* add copy in setup, test=develop

* update api spec, test=develop

* add doc, test=develop

* prettifying doc, test=develop

* Update API.spec

update api.spec, test=develop

* Update lookup_table_utils.py

test=develop

* Update lookup_table_utils.py

test=develop

* merge develop, test=develop

* merge develop, test=develop

* init fix, test=develop

* fix in downloads, test=develop

* fix in setup.in, test=develop

test=develop

test=develop

test=develop

test=develop

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

This reverts commit b1d3a1c8, reversing
changes made to f1fb64b1.

test=develop

test=develop

test=develop

`cwd` was not set before when get commit SHA. The default `cwd` is the current build directory. However, the build directory might not be the subdirectory of source. The `git` command will fail when that happened.

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test=develop

1. Non utf-8 characters within comments of OPs may lead to protobuf fail to parse_from_string
2. comment out some ops which not supported on windows
3. cuda libs may not be correctly linked to target on windows