ThomasDelteil commented on a change in pull request #10628: [MXNET-342] Fix the
multi worker Dataloader
URL: https://github.com/apache/incubator-mxnet/pull/10628#discussion_r183161704
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File path: python/mxnet/gluon/data/dataset.py
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@@ -173,8 +173,15 @@ class RecordFileDataset(Dataset):
Path to rec file.
"""
def __init__(self, filename):
- idx_file = os.path.splitext(filename)[0] + '.idx'
- self._record = recordio.MXIndexedRecordIO(idx_file, filename, 'r')
+ self._filename = filename
+ self.reload_recordfile()
+
+ def reload_recordfile(self):
+ """
+ Reload the record file.
+ """
+ idx_file = os.path.splitext(self._filename)[0] + '.idx'
+ self._record = recordio.MXIndexedRecordIO(idx_file, self._filename,
'r')
Review comment:
Ok digging a bit more, it seems that the `multiprocessing` package does not
close file descriptors since it is simply calling `os.fork()`. I have updated
the description of the PR to reflect the issue. tldr: file descriptors keep
track of the position they are in the file. When forking, all process refer to
the same file descriptor and try to move the current position at the same time,
causing a crash.
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