BrokenPipeError in Lesson 12 notebook 7-seq2seq-translation.ipynb

[jcatanza]

Under my Windows 10 64-bit system, the command

xb,yb = next(iter(data.valid_dl))

in the section labeled "Our Model"

fails with

---

BrokenPipeError Traceback (most recent call last)
in
----> 1 xb,yb = next(iter(data.valid_dl))

~\Anaconda3\envs\fastai\lib\site-packages\fastai\basic_data.py in iter(self)
73 def iter(self):
74 "Process and returns items from DataLoader."
---> 75 for b in self.dl: yield self.proc_batch(b)
76
77 @classmethod

~\Anaconda3\envs\fastai\lib\site-packages\torch\utils\data\dataloader.py in iter(self)
276 return _SingleProcessDataLoaderIter(self)
277 else:
--> 278 return _MultiProcessingDataLoaderIter(self)
279
280 @Property

~\Anaconda3\envs\fastai\lib\site-packages\torch\utils\data\dataloader.py in init(self, loader)
680 # before it starts, and del tries to join but will get:
681 # AssertionError: can only join a started process.
--> 682 w.start()
683 self.index_queues.append(index_queue)
684 self.workers.append(w)

~\Anaconda3\envs\fastai\lib\multiprocessing\process.py in start(self)
110 'daemonic processes are not allowed to have children'
111 _cleanup()
--> 112 self._popen = self._Popen(self)
113 self._sentinel = self._popen.sentinel
114 # Avoid a refcycle if the target function holds an indirect

~\Anaconda3\envs\fastai\lib\multiprocessing\context.py in _Popen(process_obj)
221 @staticmethod
222 def _Popen(process_obj):
--> 223 return _default_context.get_context().Process._Popen(process_obj)
224
225 class DefaultContext(BaseContext):

~\Anaconda3\envs\fastai\lib\multiprocessing\context.py in _Popen(process_obj)
320 def _Popen(process_obj):
321 from .popen_spawn_win32 import Popen
--> 322 return Popen(process_obj)
323
324 class SpawnContext(BaseContext):

~\Anaconda3\envs\fastai\lib\multiprocessing\popen_spawn_win32.py in init(self, process_obj)
87 try:
88 reduction.dump(prep_data, to_child)
---> 89 reduction.dump(process_obj, to_child)
90 finally:
91 set_spawning_popen(None)

~\Anaconda3\envs\fastai\lib\multiprocessing\reduction.py in dump(obj, file, protocol)
58 def dump(obj, file, protocol=None):
59 '''Replacement for pickle.dump() using ForkingPickler.'''
---> 60 ForkingPickler(file, protocol).dump(obj)
61
62 #

BrokenPipeError: [Errno 32] Broken pipe

[kashyap91]

Adding num_workers here - data = src.databunch(num_workers = 0) - is a workaround I tried. However -
1)The learn.lr_find() completes in under 15 seconds without the progress bar crossing 2%.
2)I also find input[x],targets[x].outputs[x] returning the same record for any value of x.

I am unsure if these issues are related to the BrokenPipeError and this workaround.