fixing it to work properly in multi-node environment

tests/synced_batchnorm/test_groups.py

@@ -120,7 +120,7 @@ bn_opt = optim.SGD(bn.parameters(), lr=1.0)
 for group_num in (range(args.world_size//args.group_size)):
    group_ids = range(group_num*args.group_size, (group_num+1)*args.group_size)
    cur_group = torch.distributed.new_group(ranks=group_ids)
-   if (args.local_rank//args.group_size == group_num):
+   if (torch.distributed.get_rank()//args.group_size == group_num):
        group = cur_group
 
 sbn = apex.parallel.SyncBatchNorm(feature_size, process_group=group).cuda()