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ultralytics/utils/callbacks/raytune.py

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+# Ultralytics 🚀 AGPL-3.0 License - https://ultralytics.com/license
+
+from ultralytics.utils import SETTINGS
+
+try:
+    assert SETTINGS["raytune"] is True  # verify integration is enabled
+    import ray
+    from ray import tune
+    from ray.air import session
+
+except (ImportError, AssertionError):
+    tune = None
+
+
+def on_fit_epoch_end(trainer):
+    """
+    Report training metrics to Ray Tune at epoch end when a Ray session is active.
+
+    Captures metrics from the trainer object and sends them to Ray Tune with the current epoch number,
+    enabling hyperparameter tuning optimization. Only executes when within an active Ray Tune session.
+
+    Args:
+        trainer (ultralytics.engine.trainer.BaseTrainer): The Ultralytics trainer object containing metrics and epochs.
+
+    Examples:
+        >>> # Called automatically by the Ultralytics training loop
+        >>> on_fit_epoch_end(trainer)
+
+    References:
+        Ray Tune docs: https://docs.ray.io/en/latest/tune/index.html
+    """
+    if ray.train._internal.session.get_session():  # check if Ray Tune session is active
+        metrics = trainer.metrics
+        session.report({**metrics, **{"epoch": trainer.epoch + 1}})
+
+
+callbacks = (
+    {
+        "on_fit_epoch_end": on_fit_epoch_end,
+    }
+    if tune
+    else {}
+)