add switch op design

Adding unit tests for checking that closing unbuffered channel closes all blocked senders and receivers (#8067)

* Adding unit tests for checking that closing unbuffered channel closes all blocked senders and receivers

* Fixing sleep time

init debuger.

Make NMT as normal python unittests

Add softmax into Python API.

Make recognize digits as a normal python unittest

* init

* add delete operator

* debug

* add wait

* clean code

* fix bug

* fix bug

* refine code

* remove unused code

Some optimization of CNN model computation.

* Add unite test with less receivers, more senders

* Fixed the check

* Adding an initial implementation for the unbuffered channel

* Including atomic header

* update comment

* Adding the closed attribute

* Add comments

* Updated locking mechanism

* Add simple unbuffered test

* Enhance unit test and fix bug

* Add details

Fix document errors.

* "clean code"

* "clean code"

remove libwarpctc.so in core.so and libpaddle_fluid.so

* initial commit

* add get_parameters method

* add get_parameters method

* small fix

* address comments

* address comments

* address comments

* fix

Merge branch 'develop' of github.com:baidu/Paddle into feature/make_recognize_digits_normal_unittest

Make Fit a line a normal unittest

Make image_classification as a normal python unittest

Fix compilie error

Fix default build_type env

Rename rpc ops

CI build: take -DCUDA_ARCH_NAME from environment variable

Make parallel tests bind to different GPU.

Refine feed_op