zhuolinumd

Results 2 issues of zhuolinumd

@HongguLiu have you tested your training code with multiple gpu? I got the `RuntimeError: NCCL Error 2: unhandled system error`. One gpu case is fine for me. Thanks.

@kimiyoung Can you explain the meaning and usage of the parameter `cutoffs` in the function `single_core_graph`? Can you provide some examples? Thanks