* Added kernel to is_empty_op

* Added python API

* Updated code as required

* Updated unittests

* Add topk Python API.

* Add unit test.

* Remove the repeated API.

* Move Select to concurrency.py; incorporate outputs

* CLang formatting for concurrency

* Remove extra bracket - formatting fix - 3

* Comment fix

* Fix old documentation for channel_recv

* Initial design of CSP select

* Redesign channel implementation for Select Op

* Remove unecessary header

* Initial checkin of select op, currently will read all the conditional_op in the cases block and also pull out all channels involved in the select.

* Init python select op API

* Python select bug fix when checking op creates block

* Add case_to_execute as (a) input to select, (b) into the passed inputs into the select op

* Add in addition code for select op

* Init fibonacci test from python

* implement fibonnaci sequence test

* update fib unit test

* Improve select test cases

* Shorten non-pep-8-ed lines

* Add methods on channel needed by select op

* Fix compile issues, finish implementation, still need to debug code

* Fix issue with fibonncci test, it works now!

* Change QueueMessage callback to take in an ChannelAction enum, fix select unit test

* Fix case attributes

* Fix issue with select control flow

* Make cases - previously on each selectcase conditional_block - attributes to select

* Use class constants for type of channel

* Change select op to take in "cases" attribute

* return boolean from select callback function to tell Channel if this RECV or SEND should be executed

* Improve attributes and inputs comments on select op

* Fix issues with python unit test

* Assert fibonacci final output

* Fix issue when channel name / channel var is null for "default" case in select op

* Assert base select test output

* Make QueueMessage use shared pointer and modify the order of the callback

* Fixing the order in which the callback is called

* Move channel utility methods to paddle/fluid/operators/concurrency/channel_util

* Create channel_util and move channel util methods

* Fix crash when calling select_op

* Fix deadlock

* Fix issue of channel destructor deadlock

* Fix precommit issues

* Accidentally checked in changes to beam_search_op, reverting change.

* Fix dependency issue in concurrency cmake

* add device_context dependency for concurrency target

* Add reset and guard to unique_name

* Move Pod Types from DataType enum to Type enum

* Fixed data_type.h

* Fix type in TensorDesc

* Add comment to framework.proto

* Fixed type in data_type.h

* Updated format of type in data_type.h

* Fix var_desc.h

* Fix op_kernel_type.h

* Fixed data_type_transform_test.cc

* Fix operator.h

* Fixed data_type_transform.cc

* Fixed op_kernel_type_test.cc

* Fix operator.cc

* Fixed data_layout_transform_test.cc

* Fix var_desc.cc

* Fixed assign_value_op.cc

* Fixed assign_value_op.h

* fixed protobuf.cc

* Fix data_layout_transform_test.cc and op_kernel_type_test.cc

* Fixed rnn_memory_helper_op.cc

* Fix progrma_desc_test.cc

* Fixed fill_constant_batch_size_like_op.cc

* Fix operator_test.cc

* Fixed fill_constant_op.cc

* Fixed gaussian_random_op.cc

* Fixed uniform_random_op.cc

* Fixed edit_distance_op.cc

* Fixed fill_constant_batch_size_like_op.cc

* Fixed rnn_memory_helper_op.cc

* Fixed chunk_eval_op.cc

* Fixed assign_value_op.cc

* Fixed assign_value_op.h

* Fixed cast_op.h

* Fixed cast_op.h

* Fix fill constant op

* Fixed clang for assign_value_op.cc

* Fix one_hot_op.h

* Fix one_hot_op.cc

* Fix fill_op.cc

* Fixed sum_op.cc

* Fixed sum_op clang

* Fix uniform_random_op.cc

* Fix gaussian_random_op.cc

* Fix backward.cc

* Fix protobuf.cc

* Fixed prune_test.cc

* Fixed op_registry_test.cc

* Fix data_device_transform_test.cu

* Fix travis error

* Fixed one_hot_op.cu

* Fixed op_registry_test.cc

* Fixed nccl_op.cc

* Fixing python tests

* Revert "Fixing python tests"

This reverts commit fccaa4c5.

* Fixing Pybind to remove data type

* Fixing tensor.py

* Updated the new files:

* Resolve error in merge conflict of fill_constant_batch_size_like_op.cc

And some minor fixes on comments.

* Fix parallel.do with batch norm

* Change log level

* CopyShare AllPlaces

* disable nccl test

* bring back parallel_do test

* init polynomial_decay

* test polynomial_decay

* complete polynomial_decay

* fix conditional block op

* init scalar-switch-case-op

* switch op can compile

* complete forward switch_op

* add GetMatchCaseIndex

* add switch_grad_op

* init switch Python API

* add test_switch

* support set block list in python

* fix scope problem

* complete test

* optimize test

* optimize test

* rm backward part

* clear grad op

* polynomial_decay use switch op

* revert conditional_block_op and reshape_op

* add piecewise_decay and test

* fix piecewise_decay

* try to use condition op for switch

* can work

* clean old code

* revert

* rm switch_op.cc

* optimize code

* add attr is_scalar_condition for condition_block_op

* fix comment

* fix comment

* add export

Impl scalar switch case op with condition op

neural machine translation model support beam search with while op

* "fix decode bug"

* "follow commnet"

* "fix error"

* "fix hook bug"

* fix based comment

* fix copyright

* fix based on comment

* registery is only used by layers
* Rename it to layer_function_generator

* add copyright hook

* add copyright hook

* refine copyright hook

* "test copyright hook"

* fix check style

* fix ci

* update code comments.

* update the comments.

* follow comments.