default to dropping last batch in multipack batch sampler

src/axolotl/core/trainers/base.py

@@ -33,6 +33,7 @@ from axolotl.core.trainers.utils import (
     sanitize_kwargs_for_ds_tagging,
     sanitize_kwargs_for_tagging,
 )
+from axolotl.utils import get_not_null
 from axolotl.utils.logging import get_logger
 from axolotl.utils.samplers import MultipackBatchSampler, get_dataset_lengths
 
@@ -220,7 +221,9 @@ class AxolotlTrainer(SchedulerMixin, OptimizerMixin, RngLoaderMixin, Trainer):
         }
 
         if not isinstance(dataset, torch.utils.data.IterableDataset):
-            dataloader_params["drop_last"] = self.args.dataloader_drop_last
+            dataloader_params["drop_last"] = get_not_null(
+                self.args.dataloader_drop_last, True
+            )
             if sampler_fn is not None:
                 sampler = sampler_fn(dataset)
                 if isinstance(sampler, BatchSampler):

src/axolotl/utils/__init__.py

@@ -52,3 +52,10 @@ def patch_optimized_env():
     if os.getenv("HF_HUB_ENABLE_HF_TRANSFER") is None:
         os.environ["HF_HUB_ENABLE_HF_TRANSFER"] = "1"
     set_pytorch_cuda_alloc_conf()
+
+
+def get_not_null(value, default=None):
+    """
+    return the value if it's not None, otherwise return the default value
+    """
+    return value if value is not None else default

src/axolotl/utils/samplers/multipack.py

@@ -258,7 +258,7 @@ class MultipackBatchSampler(BatchSampler):
         batch_max_len: int,  # Maximum sequence length (bin capacity)
         lengths: np.ndarray,  # Sequence lengths
         packing_efficiency_estimate: float = 1.0,  # Initial efficiency estimate
-        drop_last: bool = False,  # Whether to drop final batches (might be incomplete)
+        drop_last: bool = True,  # Whether to drop final batches (might be incomplete)
         num_count_samples: int = 16,  # Number of times to estimate batch count
         sequential: bool = False,  # Whether to use sequential packing
         group_size: int = 100_000,  # Size of groups for parallel packing