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

当您在使用CUDA进行多进程编程时，如果出现"RuntimeError: Cannot re-initialize CUDA in forked subprocess. To use CUDA with multiprocessing, you must use the 'spawn' start method"的错误提示，这是因为在使用fork方式创建子进程时，CUDA运行时不支持重新初始化CUDA。

为了解决这个问题，您可以使用'spawn'启动方法来创建子进程。在您的代码中添加以下内容可以解决这个问题：

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

这样就会使用'spawn'启动方法来创建子进程，从而解决了CUDA多进程编程的问题。同时，您可以参考以下链接来了解更多关于这个问题的信息：
- [日志提示“RuntimeError: Cannot re-initialize CUDA in forked subprocess”](https://britishgeologicalsurvey.github.io/science/python-forking-vs-spawn/)
- [Python中使用spawn或forkserver启动方法](https://www.pythonf.cn/read/65459)
- [Stack Overflow上的相关问题和解答](https://stackoverflow.com/questions/64095876/multiprocessing-fork-vs-spawn) <span class="em">1</span><span class="em">2</span><span class="em">3</span>
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