Removal of metrics deepcopy before computing the metrics (mosaicml#3180)

* remove deepcopy of metrics before calling metric.compute()

* update documentation of _compute_and_log_metrics

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Co-authored-by: Grégoire Jauvion <[email protected]>
Co-authored-by: Mihir Patel <[email protected]>

composer/trainer/trainer.py

@@ -2246,14 +2246,12 @@ def _ensure_metrics_device_and_dtype(
         return metrics
 
     def _compute_and_log_metrics(self, dataloader_label: str, metrics: Dict[str, Metric]):
-        """Computes metrics, logs the results, and updates the state with the deep-copied metrics.
+        """Computes metrics, logs the results, and updates the state with the metrics.
 
         Args:
             dataloader_label (str): The dataloader label.
             metrics (Dict[str, Metric]): The metrics to compute.
         """
-        metrics = deepcopy(metrics)
-
         # log computed metrics
         computed_metrics = {}
         for metric_name, metric in metrics.items():