internal change

grain/_src/python/dataset/transformations/packing.py

@@ -328,6 +328,35 @@ def __iter__(self) -> dataset.DatasetIterator:
         meta_features=self._meta_features,
     )
 
+  @classmethod
+  def first_row_to_pack_element(
+      cls,
+      element_feature_lengths: PyTree[int],
+      num_packing_bins: int,
+      length_struct: PyTree[int],
+      first_free_cell_per_row: PyTree[int],
+  ) -> int | None:
+    """Returns the first row to pack an element into or None if it can't fit.
+
+    The logic is the same as the one used in the packing iterator.
+
+    Args:
+      element_feature_lengths: The lengths of each feature in the element.
+      num_packing_bins: The number of packing bins.
+      length_struct: The max length of each feature.
+      first_free_cell_per_row: The first free cell per row.
+    """
+    row_or_failing_component = packing_packed_batch.PackedBatch.can_add_at_row(
+        element_feature_lengths,
+        num_packing_bins,
+        length_struct,
+        first_free_cell_per_row,
+    )
+    if row_or_failing_component.row is not None:
+      return row_or_failing_component.row
+    else:
+      return None
+
 
 class FirstFitPackDatasetIterator(dataset.DatasetIterator):
   """Iterator for the first-fit packing transformation."""

grain/_src/python/dataset/transformations/packing_test.py

@@ -1016,6 +1016,24 @@ def test_nested_feature(self, mark_as_meta_feature: bool):
       ):
         _ = next(iter(ld))
 
+  def test_first_row_to_pack_element(self):
+    element = {"a": 1, "b": 1}
+    num_packing_bins = 2
+    length_struct = {"a": 10, "b": 10}
+    first_free_cell_per_row = {
+        "a": np.zeros(num_packing_bins, dtype=np.int64),
+        "b": np.zeros(num_packing_bins, dtype=np.int64),
+    }
+    self.assertEqual(
+        packing.FirstFitPackIterDataset.first_row_to_pack_element(
+            element,
+            num_packing_bins,
+            length_struct,
+            first_free_cell_per_row,
+        ),
+        0,
+    )
+
 
 if __name__ == "__main__":
   absltest.main()