use nccl as the default comm backend

configs/r50_fpn_frcnn_1x.py

@@ -140,7 +140,7 @@ log_config = dict(
 # runtime settings
 total_epochs = 12
 device_ids = range(8)
-dist_params = dict(backend='gloo')
+dist_params = dict(backend='nccl')
 log_level = 'INFO'
 work_dir = './work_dirs/fpn_faster_rcnn_r50_1x'
 load_from = None

configs/r50_fpn_maskrcnn_1x.py

@@ -153,7 +153,7 @@ log_config = dict(
 # runtime settings
 total_epochs = 12
 device_ids = range(8)
-dist_params = dict(backend='gloo')
+dist_params = dict(backend='nccl')
 log_level = 'INFO'
 work_dir = './work_dirs/fpn_mask_rcnn_r50_1x'
 load_from = None

configs/r50_fpn_rpn_1x.py

@@ -110,7 +110,7 @@ log_config = dict(
 # yapf:enable
 # runtime settings
 total_epochs = 12
-dist_params = dict(backend='gloo')
+dist_params = dict(backend='nccl')
 log_level = 'INFO'
 work_dir = './work_dirs/fpn_rpn_r50_1x'
 load_from = None