pythonRuntimeError: Cannot re-initialize CUDA in forked subprocess. To use CUDA with multiprocessing

RuntimeError: Cannot re-initialize CUDA in forked subprocess. To use CUDA with multiprocessing, you must use the ‘spawn’ start method

• fork和spawn是构建子进程的不同方式:

fork	spawn
分叉	产卵
继承	非继承
	从头构建一个子进程，父进程的数据拷贝到子进程的空间中，拥有自己的Python解释器
变量具有与父进程中相同的id
N	在每个子进程开始时导入模块
子进程获取在 name == main 块中定义的变量	N

解决方案

if __name__=='__main__':
    torch.multiprocessing.set_start_method('spawn')

参考与更多

• 日志提示“RuntimeError: Cannot re-initialize CUDA in forked subprocess”
• https://britishgeologicalsurvey.github.io/science/python-forking-vs-spawn/
• https://www.pythonf.cn/read/65459
• https://stackoverflow.com/questions/64095876/multiprocessing-fork-vs-spawn