supports multiple NCCL communicators preserved in NCCLCommContext#19407

Merged

gavin1332 merged 2 commits intoPaddlePaddle:developfrom

Aug 27, 2019

Commits on Aug 26, 2019

supports multiple NCCL communicators preserved in NCCLCommContext
gavin1332
committed

Commits on Aug 27, 2019

add ut for c_comm_init_all operator and fix cuda resource release problem
gavin1332
committed