supports collective training with programs#18392

Merged

gavin1332 merged 5 commits intoPaddlePaddle:developfrom

gavin1332:develop

Jul 2, 2019

Commits on Jun 28, 2019

Commits on Jun 29, 2019

minor update
gavin1332
committed

Commits on Jul 2, 2019

remove collective op role to reduce the complexity of program/graph analysis
gavin1332
committed