message: Add a warning message to users who attempt to use MirroredStrategy or MultiWorkerMirroredStrategy in pure eager mode.
diff: @@ -43,6 +43,7 @@ from tensorflow.python.framework import tensor_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import control_flow_ops
  from tensorflow.python.ops import variable_scope
  +from tensorflow.python.platform import tf_logging as logging
  from tensorflow.python.training import coordinator
  from tensorflow.python.util import nest
  from tensorflow.python.util.tf_export import tf_export
  @@ -722,6 +723,14 @@ class MirroredExtended(distribute_lib.StrategyExtendedV1):
  return self._get_cross_device_ops().broadcast(tensor, destinations)
  def _call_for_each_replica(self, fn, args, kwargs):
  + if context.executing_eagerly():
  + logging.log_first_n(logging.WARN, "Using %s eagerly has significant "
  + "overhead currently. We will be working on improving "
  + "this in the future, but for now please wrap "
  + "`call_for_each_replica` or `experimental_run` or "
  + "`experimental_run_v2` inside a tf.function to get "
  + "the best performance." %
  + self._container_strategy().__class__.__name__, 5)
  return _call_for_each_replica(self._container_strategy(), self._device_map,
  fn, args, kwargs)
  