add back del logits

Author: gau-nernst

recipes/lora_finetune_single_device.py

@@ -543,6 +543,9 @@ def _loss_step(self, batch: Dict[str, torch.Tensor]) -> torch.Tensor:
         logits = logits.transpose(1, 2)
         # Compute loss
         loss = self._loss_fn(logits, labels)
+        # free logits otherwise it peaks backward memory
+        del logits
+
         return loss
 
     def train(self) -> None: