[报错解决] RuntimeError: An attempt has been made to start a new process

【报错解决】RuntimeError: An attempt has been made to start a new process…

今天来记录一个Pycharm当中的报错解决：

RuntimeError: 
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.
 
        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:
 
            if __name__ == '__main__':
                freeze_support()
                ...
 
        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable.

经过查阅资料，发现上面错误对应的报错原因是，这是因为通常情况下，在linux系统中可以使用多个子进程加载数据，而在windows系统中不能。

方案一

在windows系统中需要将进程数设置为单进程，所以我们需要将数据处理部分DataLoader中的参数 num_workers设置为0或者采用默认为0的设置，即可解决此报错问题。

这种方式的缺陷是改为采用单进程加载，速度会变慢。

方案二

代码在运行epoch之前，加上if __name__=='__main__'

方案三

加main函数，在main中调用，继续多进程加载，可以加速。

在将.py文件中的主程序用def main():囊括起来，最后添加上两行:

if __name__ == '__main__':
    main()

参考文献

[1] 【报错解决】RuntimeError: An attempt has been made to start a new process…

[2] RuntimeError: An attempt has been made to start a new process before the current process has finished its bootstrapping phase