pytorch 报错An attempt has been made to start a new process before the current process has

pytor调试过程中出现如下错误：

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.

运行如下函数出现报错

train(net,train_data,test_data,10,optimzer,criterion)

 更改为：

if __name__ == '__main__':
    train(net,train_data,test_data,10,optimzer,criterion)