Raise errors when num_workers == 0 in DataLoader (#4019)

Erotemic · apaszke · commit 5c13c6962c17 · 2017-12-05T11:07:43.000-08:00
diff --git a/torch/utils/data/dataloader.py b/torch/utils/data/dataloader.py
@@ -361,6 +361,10 @@ def __init__(self, dataset, batch_size=1, shuffle=False, sampler=None, batch_sam
         if sampler is not None and shuffle:
             raise ValueError('sampler is mutually exclusive with shuffle')
 
+        if self.num_workers < 0:
+            raise ValueError('num_workers cannot be negative; '
+                             'use num_workers=0 to disable multiprocessing.')
+
         if batch_sampler is None:
             if sampler is None:
                 if shuffle:
