’_MultiProcessingDataLoaderIter’ erro when num_workers>0
environment： remote Linux+ Pycharm IDE + PyTorch 1.8.0
When I tried to debug my code with Pycharm IDE, there was a bug showing that _MultiProcessingDataLoaderIter error.
Then I found that when I set ‘num_workers_per_gpu’ > 0, such bug would happen.
There is no bug in my code, cause when I directly ran it, there is no any error.
Such bug just happened when only Debug mode. And when I set num_workers_per_gpu =0, there was no bug in any mode. It looks like so strange:
(1) num_workers_per_gpu =0,
debug mode 
run mode:
(2) num_workers_per_gpu >0,
debug mode: 
run mode:
It seems when Debug mode, the following loop would break uncorrectly (the condition of while loop here would set false):
while self._rcvd_idx < self._send_idx:
info = self._task_info[self._rcvd_idx]
worker_id = info[0]
if len(info) == 2 or self._workers_status[worker_id]: # has data or is still active
break
del self._task_info[self._rcvd_idx]
self._rcvd_idx += 1
else:
# no valid `self._rcvd_idx` is found (i.e., didn't break)
if not self._persistent_workers:
self._shutdown_workers()
raise StopIteration
I do not know how to solve it. And I checked torch.batchSampler, the reason that conditon becomes false could be that my sampler catches no data yet. But it just my own guess.