Remove random sampling

lerobot/common/datasets/abstract.py

@@ -130,13 +130,13 @@ class AbstractDataset(TensorDictReplayBuffer):
         else:
             self._transform = transform
 
-    def compute_or_load_stats(self, num_batch: int | None = None, batch_size: int = 32) -> TensorDict:
+    def compute_or_load_stats(self, batch_size: int = 32) -> TensorDict:
         stats_path = self.data_dir / "stats.pth"
         if stats_path.exists():
             stats = torch.load(stats_path)
         else:
             logging.info(f"compute_stats and save to {stats_path}")
-            stats = self._compute_stats(num_batch, batch_size)
+            stats = self._compute_stats(batch_size)
             torch.save(stats, stats_path)
         return stats
 
@@ -151,18 +151,14 @@ class AbstractDataset(TensorDictReplayBuffer):
             self.data_dir = self.root / self.dataset_id
         return TensorStorage(TensorDict.load_memmap(self.data_dir / "replay_buffer"))
 
-    def _compute_stats(self, num_batch: int | None = None, batch_size: int = 32):
+    def _compute_stats(self, batch_size: int = 32):
-        """Compute dataset statistics including minimum, maximum, mean, and standard deviation.
+        """Compute dataset statistics including minimum, maximum, mean, and standard deviation."""
-
-        If `num_batch` is specified, we draw `num_batch` batches of size `batch_size` to compute the
-        statistics. If `num_batch` is not specified, we just consume the whole dataset (default).
-        """
         rb = TensorDictReplayBuffer(
             storage=self._storage,
             batch_size=32,
             prefetch=True,
             # Note: Due to be refactored soon. The point is that we should go through the whole dataset.
-            sampler=SamplerWithoutReplacement(drop_last=False, shuffle=num_batch is not None),
+            sampler=SamplerWithoutReplacement(drop_last=False, shuffle=False),
         )
 
         # mean and std will be computed incrementally while max and min will track the running value.
@@ -177,7 +173,7 @@ class AbstractDataset(TensorDictReplayBuffer):
         # Note: Due to be refactored soon. The point of storing `first_batch` is to make sure we don't get
         # surprises when rerunning the sampler.
         first_batch = None
-        for _ in tqdm.tqdm(num_batch or range(ceil(len(rb) / batch_size))):
+        for _ in tqdm.tqdm(range(ceil(len(rb) / batch_size))):
             batch = rb.sample()
             if first_batch is None:
                 first_batch = deepcopy(batch)
@@ -193,7 +189,7 @@ class AbstractDataset(TensorDictReplayBuffer):
 
         # Compute std
         first_batch_ = None
-        for _ in tqdm.tqdm(num_batch or range(ceil(len(rb) / batch_size))):
+        for _ in tqdm.tqdm(range(ceil(len(rb) / batch_size))):
             batch = rb.sample()
             # Sanity check to make sure the batches are still in the same order as before.
             if first_batch_ is None:

tests/test_datasets.py

@@ -53,7 +53,9 @@ def test_compute_stats():
             batch_size=len(buffer),
             sampler=SamplerWithoutReplacement(),
     ).sample().float()
-    computed_stats = buffer._compute_stats()
+    # Note: we set the batch size to be smaller than the whole dataset to make sure we are testing batched
+    # computation of the statistics.
+    computed_stats = buffer._compute_stats(batch_size=int(len(all_data) * 0.75))
     for k, pattern in buffer.stats_patterns.items():
         expected_mean = einops.reduce(all_data[k], pattern, "mean")
         assert torch.allclose(computed_stats[k]["mean"], expected_mean)