A issue about file worker.py

when the first evolution step finish. I get a situation about worker.py .I running in ubuntu.
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..Error information.....
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All workers are done
Traceback (most recent call last):
File "experiment.py", line 23, in
tournament.step()
File "/home/shareData/Yu/temp/evolution/gp.py", line 49, in step
self.evaluate()
File "/home/shareData/Yu/temp/evolution/gp.py", line 97, in evaluate
self.population, returns = workerpool.start(self.population)
File "/home/shareData/Yu/temp/evolution/worker.py", line 49, in start
score, net = self._results.get()
File "/root/anaconda3/lib/python3.7/multiprocessing/queues.py", line 113, in get
return _ForkingPickler.loads(res)
File "/root/anaconda3/lib/python3.7/site-packages/torch/multiprocessing/reductions.py", line 276, in rebuild_storage_fd
fd = df.detach()
File "/root/anaconda3/lib/python3.7/multiprocessing/resource_sharer.py", line 57, in detach
with _resource_sharer.get_connection(self._id) as conn:
File "/root/anaconda3/lib/python3.7/multiprocessing/resource_sharer.py", line 87, in get_connection
c = Client(address, authkey=process.current_process().authkey)
File "/root/anaconda3/lib/python3.7/multiprocessing/connection.py", line 492, in Client
c = SocketClient(address)
File "/root/anaconda3/lib/python3.7/multiprocessing/connection.py", line 619, in SocketClient
s.connect(address)
FileNotFoundError: [Errno 2] No such file or directory

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I didn't know what was wrong.Thank you!