Distributed package doesn‘t have NCCL built in

Distributed package doesn't have NCCL built in

问题描述：
python在windows环境下dist.init_process_group(backend, rank, world_size)处报错‘RuntimeError: Distributed package doesn’t have NCCL built in’，具体信息如下：

  File "D:\Software\Anaconda\Anaconda3\envs\segmenter\lib\site-packages\torch\distributed\distributed_c10d.py", line 531, in init_process_group
    timeout=timeout)
  File "D:\Software\Anaconda\Anaconda3\envs\segmenter\lib\site-packages\torch\distributed\distributed_c10d.py", line 625, in _new_process_group_helper
    raise RuntimeError("Distributed package doesn't have NCCL "
RuntimeError: Distributed package doesn't have NCCL built in

原因分析：
windows不支持NCCL backend

解决方案：
在dist.init_process_group语句之前添加backend=‘gloo’，也就是在windows中使用GLOO替代NCCL。
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原文链接：https://blog.csdn.net/StarCap/article/details/120070425

insightface训练代码：

try:
    world_size =1# int(os.environ["WORLD_SIZE"])
    rank =0# int(os.environ["RANK"])
    # distributed.init_process_group("nccl")
    distributed.init_process_group("gloo")
except KeyError:
    world_size = 1
    rank = 0
    distributed.init_process_group(
        backend="nccl",
        init_method="tcp://127.0.0.1:12584",
        rank=rank,
        world_size=world_size,
    )