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pytorch_lightning/metrics/converters.py

@@ -325,23 +325,23 @@ def sync_horovod_if_available(
         reduced value
     """
 
-    if HOROVOD_AVAILABLE and hvd.is_initialized():
-        if group is not None:
-            raise ValueError("Horovod does not support allreduce using a subcommunicator at "
-                             "this time. Unset `group`.")
-
-        if reduce_op is None or reduce_op == "sum":
-            reduce_op = hvd.Sum
-        elif isinstance(reduce_op, str) and reduce_op in ("avg", "mean"):
-            reduce_op = hvd.Average
-        else:
-            raise ValueError(f"unrecognized `reduce_op`: {reduce_op}")
-
-        # sync all processes before reduction
-        hvd.join()
-        result = hvd.allreduce(result, op=reduce_op)
-
-    return result
+    if not (HOROVOD_AVAILABLE and hvd.is_initialized()):
+        return result
+    if group is not None:
+        raise ValueError(
+            "Horovod does not support allreduce using a subcommunicator at this time. Unset `group`."
+        )
+
+    if reduce_op is None or reduce_op == "sum":
+        reduce_op = hvd.Sum
+    elif isinstance(reduce_op, str) and reduce_op in ("avg", "mean"):
+        reduce_op = hvd.Average
+    else:
+        raise ValueError(f"unrecognized `reduce_op`: {reduce_op}")
+
+    # sync all processes before reduction
+    hvd.join()
+    return hvd.allreduce(result, op=reduce_op)
 
 
 def at_least_1d(tensor: Union[np.ndarray, torch.Tensor]) -> Union[np.ndarray, torch.Tensor]: