Downgrade boost to fit manylinux

Fix send op data race

Make notest_dist_image_classification  consistent with distributed implementation in others. (#7899)

* Make this file consistent with others

* fixed style

* add Channle

* refine Channel

* Add one_hot operator.

* Add more unit tests.

* initial commit

* add new executor run function

* fix bug

* fix multiple definition of feed_fetch_method issue

* fix cmake

* fix tensor copy error

* refine executor code

* add comments

* temporary modification

* address comments

* fix bug

std::vector<bool> is not safe for concurrent write, even to difference indices.
More discussion:
https://stackoverflow.com/questions/48452611/is-stdfuturewait-a-memory-barrier-i-can-not-explain-this-data-race

Fix the context vector calculation in test_rnn_encoder_decoder.py.

Fix dist transpiler bug

Add python wrapper for multiplex operator.

Add noavx-openblas whl package download link

Add lstm with recurrent projection layer operator

enhance the machine_translation model in unittest.

Feature/add demo for parallel.do

* fix call once logic

* clean up

* further clean up

* fix root number

* fix call once logic

* clean up

* further clean up

Transpiler: fix pserver crash due to split var name check.

* Add distributed implementation for recommender system

* Addressing code review feedback

In notest_dist_label_semantic_roles.py, "emb" is matched with
"embedding_1.w_0", but they are two irrevalent vars.

Fixes: https://github.com/PaddlePaddle/Paddle/issues/7701

fix openblas build

* remove pick dependency

* fix bug

* small fix

* modify executor.py for save and load

* clean code

* Add usage example

* refine executor run function

* fix bug

* refine executor code

* fix block bug

* fix comments

* fix bug

* fix pass num