DPO fixes v2 (#1174)

* check for length before trying to remove it

* add validation for sample packing with RLHF

src/axolotl/core/trainer_builder.py

@@ -227,7 +227,8 @@ def _get_eval_sampler(
     def get_train_dataloader(self) -> DataLoader:
         if self.args.sample_packing and not self.args.pretraining:
             train_dataset = self.train_dataset
-            train_dataset = train_dataset.remove_columns(["length"])
+            if "length" in train_dataset.features.keys():
+                train_dataset = train_dataset.remove_columns(["length"])
             data_collator = self.data_collator
             dataloader_params = {
                 "batch_size": self._train_batch_size,

src/axolotl/utils/config.py

@@ -204,6 +204,9 @@ def validate_config(cfg):
     if cfg.max_packed_sequence_len:
         raise DeprecationWarning("`max_packed_sequence_len` is no longer supported")
 
+    if cfg.sample_packing and cfg.rl:
+        raise ValueError("`sample_packing: true` does not work with RLHF training")
+
     if cfg.sample_packing and not cfg.pad_to_sequence_len:
         LOG.warning(
             "`pad_to_sequence_len: true` is recommended when using sample_packing"