Move NaFlexCollate with dataset, remove stand alone collate_fn and remove redundancy

Author: rwightman

timm/data/naflex_dataset.py

@@ -59,63 +59,65 @@ def calculate_batch_size(
     return batch_size
 
 
-def _collate_batch(
-    batch_samples: List[Tuple[Dict[str, torch.Tensor], Any]],
-    target_seq_len: int
-    ) -> Tuple[Dict[str, torch.Tensor], torch.Tensor]:
-    """Collates processed samples into a batch, padding/truncating to target_seq_len."""
-    batch_patch_data = [item[0] for item in batch_samples]
-    batch_labels = [item[1] for item in batch_samples]
-
-    if not batch_patch_data:
-         return {}, torch.empty(0)
-
-    batch_size = len(batch_patch_data)
-    patch_dim = batch_patch_data[0]['patches'].shape[1]
-
-    # Initialize tensors with target sequence length
-    patches_batch = torch.zeros((batch_size, target_seq_len, patch_dim), dtype=torch.float32)
-    patch_coord_batch = torch.zeros((batch_size, target_seq_len, 2), dtype=torch.int64)
-    patch_valid_batch = torch.zeros((batch_size, target_seq_len), dtype=torch.bool) # Use bool
-
-    for i, data in enumerate(batch_patch_data):
-        num_patches = data['patches'].shape[0]
-        # Take min(num_patches, target_seq_len) patches
-        n_copy = min(num_patches, target_seq_len)
-
-        patches_batch[i, :n_copy] = data['patches'][:n_copy]
-        patch_coord_batch[i, :n_copy] = data['patch_coord'][:n_copy]
-        patch_valid_batch[i, :n_copy] = data['patch_valid'][:n_copy] # Copy validity flags
-
-    # Create the final input dict
-    input_dict = {
-        'patches': patches_batch,
-        'patch_coord': patch_coord_batch,
-        'patch_valid': patch_valid_batch, # Boolean mask
-        # Note: 'seq_length' might be ambiguous. The target length is target_seq_len.
-        # The actual number of valid patches per sample varies.
-        # 'patch_valid' mask is the most reliable source of truth.
-    }
-
-    # Attempt to stack labels if they are tensors, otherwise return list
-    try:
-        if isinstance(batch_labels[0], torch.Tensor):
-            labels_tensor = torch.stack(batch_labels)
+class NaFlexCollator:
+    """Custom collator for batching NaFlex-style variable-resolution images."""
+
+    def __init__(
+            self,
+            max_seq_len=None,
+    ):
+        self.max_seq_len = max_seq_len or 576  # Default ViT-B/16 sequence length (577 = 24*24)
+
+    def __call__(self, batch):
+        """
+        Args:
+            batch: List of tuples (patch_dict, target)
+
+        Returns:
+            A tuple of (input_dict, targets) where input_dict contains:
+                - patches: Padded tensor of patches
+                - patch_coord: Coordinates for each patch (y, x)
+                - patch_valid: Valid indicators
+        """
+        assert isinstance(batch[0], tuple)
+        batch_size = len(batch)
+
+        # Extract targets
+        # FIXME need to handle dense (float) targets or always done downstream of this?
+        targets = torch.tensor([item[1] for item in batch], dtype=torch.int64)
+
+        # Get patch dictionaries
+        patch_dicts = [item[0] for item in batch]
+
+        # If we have a maximum sequence length constraint, ensure we don't exceed it
+        if self.max_seq_len is not None:
+            max_patches = self.max_seq_len
         else:
-            # Convert numerical types to tensor, keep others as list (or handle specific types)
-            if isinstance(batch_labels[0], (int, float)):
-                 labels_tensor = torch.tensor(batch_labels)
-            else:
-                 # Cannot convert non-numerical labels easily, return as list
-                 # Or handle specific conversion if needed
-                 # For FakeDataset, labels are ints, so this works
-                 labels_tensor = torch.tensor(batch_labels) # Assuming labels are numerical
-    except Exception:
-        # Fallback if stacking fails (e.g., different shapes, types)
-        print("Warning: Could not stack labels into a tensor. Returning list of labels.")
-        labels_tensor = batch_labels # Return as list
+            # Find the maximum number of patches in this batch
+            max_patches = max(item['patches'].shape[0] for item in patch_dicts)
+
+        # Get patch dimensionality
+        patch_dim = patch_dicts[0]['patches'].shape[1]
+
+        # Prepare tensors for the batch
+        patches = torch.zeros((batch_size, max_patches, patch_dim), dtype=torch.float32)
+        patch_coord = torch.zeros((batch_size, max_patches, 2), dtype=torch.int64)  # [B, N, 2] for (y, x)
+        patch_valid = torch.zeros((batch_size, max_patches), dtype=torch.bool)
+
+        # Fill in the tensors
+        for i, patch_dict in enumerate(patch_dicts):
+            num_patches = min(patch_dict['patches'].shape[0], max_patches)
 
-    return input_dict, labels_tensor
+            patches[i, :num_patches] = patch_dict['patches'][:num_patches]
+            patch_coord[i, :num_patches] = patch_dict['patch_coord'][:num_patches]
+            patch_valid[i, :num_patches] = patch_dict['patch_valid'][:num_patches]
+
+        return {
+            'patches': patches,
+            'patch_coord': patch_coord,
+            'patch_valid': patch_valid,
+            'seq_len': max_patches,
+        }, targets
 
 
 class VariableSeqMapWrapper(IterableDataset):
@@ -161,15 +163,15 @@ def __init__(
         self.epoch = epoch
         self.batch_divisor = batch_divisor
 
-        # Pre-initialize transforms for each sequence length
+        # Pre-initialize transforms and collate fns for each sequence length
         self.transforms: Dict[int, Optional[Callable]] = {}
-        if transform_factory:
-            for seq_len in self.seq_lens:
+        self.collate_fns: Dict[int, Callable] = {}
+        for seq_len in self.seq_lens:
+            if transform_factory:
                 self.transforms[seq_len] = transform_factory(max_seq_len=seq_len, patch_size=self.patch_size)
-        else:
-             for seq_len in self.seq_lens:
-                 self.transforms[seq_len] = None # No transform
-
+            else:
+                self.transforms[seq_len] = None # No transform
+            self.collate_fns[seq_len] = NaFlexCollator(seq_len)
         self.patchifier = Patchify(self.patch_size)
 
         # --- Canonical Schedule Calculation (Done Once) ---
@@ -417,6 +419,6 @@ def __iter__(self) -> Iterator[Tuple[Dict[str, torch.Tensor], torch.Tensor]]:
 
             # Collate the processed samples into a batch
             if batch_samples: # Only yield if we successfully processed samples
-                yield _collate_batch(batch_samples, seq_len)
+                yield self.collate_fns[seq_len](batch_samples)
 
             # If batch_samples is empty after processing 'indices', an empty batch is skipped.

timm/data/naflex_loader.py

@@ -7,74 +7,10 @@
 
 from .constants import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
 from .loader import _worker_init
-from .naflex_dataset import VariableSeqMapWrapper
+from .naflex_dataset import VariableSeqMapWrapper, NaFlexCollator
 from .transforms_factory import create_transform
 
 
-class NaFlexCollator:
-    """Custom collator for batching NaFlex-style variable-resolution images."""
-
-    def __init__(
-            self,
-            patch_size=16,
-            max_seq_len=None,
-    ):
-        self.patch_size = patch_size
-        self.max_seq_len = max_seq_len or 576  # Default ViT-B/16 sequence length (577 = 24*24)
-
-    def __call__(self, batch):
-        """
-        Args:
-            batch: List of tuples (patch_dict, target)
-
-        Returns:
-            A tuple of (input_dict, targets) where input_dict contains:
-                - patches: Padded tensor of patches
-                - patch_coord: Coordinates for each patch (y, x)
-                - patch_valid: Valid indicators
-        """
-        assert isinstance(batch[0], tuple)
-        batch_size = len(batch)
-
-        # Resize to final size based on seq_len and patchify
-
-        # Extract targets
-        targets = torch.tensor([item[1] for item in batch], dtype=torch.int64)
-
-        # Get patch dictionaries
-        patch_dicts = [item[0] for item in batch]
-
-        # If we have a maximum sequence length constraint, ensure we don't exceed it
-        if self.max_seq_len is not None:
-            max_patches = self.max_seq_len
-        else:
-            # Find the maximum number of patches in this batch
-            max_patches = max(item['patches'].shape[0] for item in patch_dicts)
-
-        # Get patch dimensionality
-        patch_dim = patch_dicts[0]['patches'].shape[1]
-
-        # Prepare tensors for the batch
-        patches = torch.zeros((batch_size, max_patches, patch_dim), dtype=torch.float32)
-        patch_coord = torch.zeros((batch_size, max_patches, 2), dtype=torch.int64)  # [B, N, 2] for (y, x)
-        patch_valid = torch.zeros((batch_size, max_patches), dtype=torch.bool)
-
-        # Fill in the tensors
-        for i, patch_dict in enumerate(patch_dicts):
-            num_patches = min(patch_dict['patches'].shape[0], max_patches)
-
-            patches[i, :num_patches] = patch_dict['patches'][:num_patches]
-            patch_coord[i, :num_patches] = patch_dict['patch_coord'][:num_patches]
-            patch_valid[i, :num_patches] = patch_dict['patch_valid'][:num_patches]
-
-        return {
-            'patches': patches,
-            'patch_coord': patch_coord,
-            'patch_valid': patch_valid,
-            'seq_len': max_patches,
-        }, targets
-
-
 class NaFlexPrefetchLoader:
     """Data prefetcher for NaFlex format which normalizes patches."""
 
@@ -261,9 +197,7 @@ def create_naflex_loader(
         # NOTE: Collation is handled by the dataset wrapper for training
         # Create the collator (handles fixed-size collation)
         # collate_fn = NaFlexCollator(
-        #     patch_size=patch_size,
         #     max_seq_len=max(seq_lens) + 1,  # +1 for class token
-        #     use_prefetcher=use_prefetcher
         # )
 
         loader = torch.utils.data.DataLoader(
@@ -303,10 +237,7 @@ def create_naflex_loader(
         )
 
         # Create the collator
-        collate_fn = NaFlexCollator(
-            patch_size=patch_size,
-            max_seq_len=max_seq_len,
-        )
+        collate_fn = NaFlexCollator(max_seq_len=max_seq_len)
 
         # Handle distributed training
         sampler = None