fix typo in faq.

* first commit

* Python API for while op

* Python Unittest for simple while_op forward

* fix out to be list

* Fix UT

* VarType

* Fix several bugs

* Fix bug

* Fix bug

* Fix Bug

* Fix bug

* Fix unittest

* Remove debug log

* Add comments

* add PADDLE_ENFORCE

* while_grad_op first commit

* Add `BlockDescBind::FindRecursiveOrCreateVar()` and fix bugs

* refine code

* fix unittest bug

Remove fill_constant_batch_size_like_op.h and clean some operator codes.

Add chunk eval op

fix EQUAL unknown

* Adding operator assignment

* Adding documentation to layers.py

* Removing file from another PR

Feature/increase cpu

Remove unused g_main_program in tests

* Fix attribute naming for momentum_op

* Fix minor typo in comment

* Fix attribute name

* Fix names in test_optimizer

* Fix python wrapper

Add `lod_array_length` operator

remove unused INTEL_MKL_ROOT etc.

fix typo

Enable hidden/cell state initialization and enhance unit testing in LSTM operator.

Bug fix for ScaleSubRegionLayer

NCE does not need to set its activation.

Update annotations of layers.py.

Add ScaleSubRegion Layer.

add clip_by_norm op

update tags of MKLML and MKL-DNN