SimpleDataLoaderMapProvider sample batches without replacement if num_samples is not specified

Summary: Samples batches without replacement if the number of samples is not specified. This makes sure that we always iterate over the whole dataset in each epoch.

Reviewed By: bottler

Differential Revision: D39270786

fbshipit-source-id: 0c983d1f5e0af711463abfb23939bc0d2b5172a0

Author: davnov134

Diff for: pytorch3d/implicitron/dataset/data_loader_map_provider.py

@@ -130,7 +130,14 @@ def _make_data_loader(
             num_samples = self.batch_size * num_batches
         else:
             num_samples = None
-        sampler = RandomSampler(dataset, replacement=True, num_samples=num_samples)
+
+        # sample with replacement only if a custom number of samples is specified
+        sampler = RandomSampler(
+            dataset,
+            replacement=num_samples is not None,
+            num_samples=num_samples,
+        )
+
         batch_sampler = BatchSampler(sampler, self.batch_size, drop_last=True)
         return DataLoader(
             dataset,