fix

Author: awaelchli

src/lightning/fabric/utilities/distributed.py

@@ -119,11 +119,11 @@ def _sync_ddp(result: Tensor, group: Optional[Any] = None, reduce_op: Optional[U
  The reduced value.
  """
  divide_by_world_size = False
- reduce_op = "avg" if reduce_op == "mean" else reduce_op
  group = torch.distributed.group.WORLD if group is None else group
 
  op: Optional[ReduceOp]
  if isinstance(reduce_op, str):
+ reduce_op = "avg" if reduce_op == "mean" else reduce_op
  if reduce_op.lower() == "avg" and torch.distributed.get_backend(group) == "gloo":
  # The GLOO backend does not support the `ReduceOp.AVG` operation
  op = ReduceOp.SUM # type: ignore[assignment]