Repository: huggingface/transformers
Pull request: Remove call to `.item` in `get_batch_samples`

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Following https://github.com/huggingface/transformers/issues/35086 and https://github.com/huggingface/transformers/pull/35115, fixes were applied to the `get_batch_samples` method. However, a call to `.item` was introduced, which triggers a device synchronisation + device-host communication, leading to significant throughput regression in some cases.

See also https://github.com/huggingface/optimum-habana/pull/1869.


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Changed files:
filename: src/transformers/trainer.py
patch: @@ -2505,7 +2505,7 @@ def _inner_training_loop(
             for _ in range(total_updates):
                 update_step += 1
                 num_batches = args.gradient_accumulation_steps if update_step != (total_updates - 1) else remainder
-                batch_samples, num_items_in_batch = self.get_batch_samples(epoch_iterator, num_batches)
+                batch_samples, num_items_in_batch = self.get_batch_samples(epoch_iterator, num_batches, args.device)
                 for i, inputs in enumerate(batch_samples):
                     step += 1
                     do_sync_step = (step + 1) % args.gradient_accumulation_steps == 0 or (step + 1) == steps_in_epoch
@@ -5216,7 +5216,7 @@ def _fsdp_qlora_plugin_updates(self):
                     self.model.hf_quantizer.quantization_config.bnb_4bit_quant_storage, override=True
                 )
 
-    def get_batch_samples(self, epoch_iterator, num_batches):
+    def get_batch_samples(self, epoch_iterator, num_batches, device):
         batch_samples = []
         num_items_in_batch = None
         for _ in range(num_batches):
@@ -5232,11 +5232,12 @@ def get_batch_samples(self, epoch_iterator, num_batches):
             except (TypeError, AttributeError):
                 pass
 
-        if self.args.average_tokens_across_devices and num_items_in_batch is not None:
-            num_items_in_batch = self.accelerator.gather(num_items_in_batch).sum().item()
+        if num_items_in_batch is not None:
+            if self.args.average_tokens_across_devices:
+                num_items_in_batch = self.accelerator.gather(num_items_in_batch).sum()
 
-        if torch.is_tensor(num_items_in_batch):
-            num_items_in_batch = num_items_in_batch.item()
+            if torch.is_tensor(num_items_in_batch):
+                num_items_in_batch = num_items_in_batch.to(device)
 
         return batch_samples, num_items_in_batch