* flush denormals to zero, test=develop

* add comments, test=develop

* polish framework error message part 4

* fix type error

* fix message error

* polish by review comments

* Added DNNL cache management for DyGraph

* move FLAGS_use_mkldnn to more general CMakeLists, getu use of the flag in ClearGradients

* missing file

* Fixes after review

* Bringing back original idea of place for 'use_mkldnn' flag to be accessible from platform nad imperative.

* Removed duplicate and added docs

* Fixes for CI

* make DisableGlogInfo able to mute all logs in inference. 

Add examples for error message writing specification - NotFound, OutOfRange, AlreadyExists, PermissionDenied (#21134)

* add examples for error msg spec, test=develop

* change ENFORCE to ENFORCE_**, test=develop

* add more already exists examples, test=develop

* AsyncExecutor: C++ side

* Google naming conventions

* Rename MultiExecutor to AsyncExecutor

* pybind with async_executor

* Naming convention

* remove some flags and unused code

* add refactored file of async_executor and data_feed

* clear async executor interface and add data feed factory

* split async executor into executor_thread_worker and async_executor, refactor pybind, add datafeed and corresponding proto

* Fix async_executor interfaces: 1) Remove all protobufs; 2) Stop after each epoch

* refine async_executor_refactor.cc

* add some files about datafeed

* Revert "add some files about datafeed"

This reverts commit 8ee8133a.

* Interface rework

* add MultiSlotDataFeed

* Creating DataFeedDesc from .proto file, then manipulate it (add/del fields etc) from python side

* update data_feed for add MultiSlotDataFeed

* update datafeed and async_executor to run bow_net demo

* fix bug that finish_set_filelist failed in multithread

* delete finish_binding_memory_(flag), because it can not be marked under the current interface

* Fix bug

* update async_executor.py for support set_use_slots

* update async_executor.py for support set_use_slots and set set_dense_slots

* fix bug that when the number of files is less than the number of threads, it will fetch nan

* remove redundant code, and make executor exit when set a illegal queue size

* add batch_size check

* add MultiSlotDesc

* Revert "add MultiSlotDesc"

This reverts commit 2e72ebfa.

* add some checkpoint in DataFeedDesc

* add CheckFile function in MultiSlotDataFeed

* update something error info

* fix deaded lock bug

* Fix fetch variable

* Merge error

* fix code style in async_executor

* using one lock blocking queue replace two lock blocking queue because of some bugs

* update code style

* add utest for data_feed

* Fix fetch var

* update utest for data_feed for multithread

* update SetFileList info

* fix bug in utest of data_feed

* Add comments for python

* Add comments for python code

* Fix pybind.cc with new pybind11 version

* add note for DataFeedDesc's set_use_slots function

* Add save_model

* update data_feed_test for multi-type

* add comment for executor_thread_worker

* Remove unused code

* update data_feed_test for generate test data file

* removed unnecessary interfaces and add comments

* c++ style check

* update data_feed.cc

* AsyncExecutor: C++ side

Google naming conventions

Rename MultiExecutor to AsyncExecutor

pybind with async_executor

Naming convention

remove some flags and unused code

add refactored file of async_executor and data_feed

clear async executor interface and add data feed factory

split async executor into executor_thread_worker and async_executor, refactor pybind, add datafeed and corresponding proto

Fix async_executor interfaces: 1) Remove all protobufs; 2) Stop after each epoch

refine async_executor_refactor.cc

add some files about datafeed

Revert "add some files about datafeed"

This reverts commit 8ee8133a.

add MultiSlotDataFeed

Interface rework

Creating DataFeedDesc from .proto file, then manipulate it (add/del fields etc) from python side

update datafeed and async_executor to run bow_net demo

update async_executor.py for support set_use_slots

Fix bug

update async_executor.py for support set_use_slots and set set_dense_slots

fix bug that when the number of files is less than the number of threads, it will fetch nan

remove redundant code, and make executor exit when set a illegal queue size

add MultiSlotDesc

Revert "add MultiSlotDesc"

This reverts commit 2e72ebfa.

add some checkpoint in DataFeedDesc

Fix fetch variable

fix code style in async_executor

Fix fetch var

add utest for data_feed

Add comments for python

update utest for data_feed for multithread

fix bug in utest of data_feed

Add comments for python code

Fix pybind.cc with new pybind11 version

add note for DataFeedDesc's set_use_slots function

update data_feed_test for multi-type

Add save_model

update data_feed_test for generate test data file

removed unnecessary interfaces and add comments

add comment for executor_thread_worker

Remove unused code

update data_feed.cc

c++ style check

* commit for code style

* commit for code style

* commit for code style

* commit for code style

* Comment away __init__ in async_executor.py

* clang-format fix test=develop

* use PADDLE_THROW instead of exit(-1); use unique_ptr to manage scope var in data_feed_test.cc

* commit for update code style

* commit for update code style

* Add async_executor demo; Remove some methods
test=develop

* commit for update code style

* commit for update code style

* commit for update code style

* update API.spec

* AsyncExecutor
test=develop

* AsyncExecutor
test=develop

* AsyncExecutor
test=develop

* AsyncExecutor
test=develop

* Fix API.spec
test=develop

* Fix API.spec
test=develop

* Fix windows build error
test=develop

* FIx windows build error
test=develop

* FIx windows build error
test=develop

* FIx windows build error
test=develop

* Fix Windows Build
test=develop

* Fix Windows Build
test=develop

* Fix Windows Build
test=develop

* Fix code style
test=develop

* Fix code style
test=develop

* update datafeed

* Fix code style
test=develop

* update data_feed_test for test Tensor test=develop

* Fix code style
test=develop

* Fix windows build failure
test=develop

* Fix code style and windows build failure
test=develop

* Fix PYTHON3.5 build failure
test=develop

* AsyncExecutor API
test=develop

* fix inference on gpu out of mem

the transfer logic in operator.cc will keep creating new scopes.

Fix code to support cpplint syntax check

test=develop

test=develop

test=develop

test=develop

test=develop

This can cause a lot of problem:
1. Wrong operator implementation, Op can get a wrong type without failure.
2. Anytype can be Get without defined in VarType.

Also fix wrong STEP_SCOPE usage.

test=develop

test=develop

test=develop

test=develop

- add naive executor
- fix concurrency performance issue