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。