查了网上说的教程，说是
When using spawn you should guard the part that launches the job in if __name__ == '__main__':
set_start_method should also go there, and everything will run fine.
所以把任务放到了if __name__ == '__main__':下面
后面有人说
You might have other files in your project which also have a if __name__ == '__main__':. One workaround is to call the set_start_method with the force argument as: set_start_method('forkserver', force=True). This solved the issue for me.
又改成了multiprocessing.set_start_method('forkserver', force=True)
可算是跑起来了
