# Copyright 2019 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
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# ==============================================================================

"""API for enabling v2 control flow."""

from tensorflow.python.framework import ops
from tensorflow.python.ops import control_flow_util
from tensorflow.python.platform import tf_logging as logging
from tensorflow.python.util.tf_export import tf_export


@tf_export(v1=["enable_control_flow_v2"])
def enable_control_flow_v2():  # pylint: disable=invalid-name
  """Use control flow v2.

  control flow v2 (cfv2) is an improved version of control flow in TensorFlow
  with support for higher order derivatives. Enabling cfv2 will change the
  graph/function representation of control flow, e.g., `tf.while_loop` and
  `tf.cond` will generate functional `While` and `If` ops instead of low-level
  `Switch`, `Merge` etc. ops. Note: Importing and running graphs exported
  with old control flow will still be supported.

  Calling tf.enable_control_flow_v2() lets you opt-in to this TensorFlow 2.0
  feature.

  Note: v2 control flow is always enabled inside of tf.function. Calling this
  function is not required.
  """
  # pylint: disable=protected-access
  logging.vlog(1, "Enabling control flow v2")
  ops._control_flow_api_gauge.get_cell().set(True)
  control_flow_util.ENABLE_CONTROL_FLOW_V2 = True


@tf_export(v1=["disable_control_flow_v2"])
def disable_control_flow_v2():  # pylint: disable=invalid-name
  """Opts out of control flow v2.

  Note: v2 control flow is always enabled inside of tf.function. Calling this
  function has no effect in that case.

  If your code needs tf.disable_control_flow_v2() to be called to work
  properly please file a bug.
  """
  # pylint: disable=protected-access
  logging.vlog(1, "Disabling control flow v2")
  ops._control_flow_api_gauge.get_cell().set(False)
  control_flow_util.ENABLE_CONTROL_FLOW_V2 = False


@tf_export(v1=["control_flow_v2_enabled"])
def control_flow_v2_enabled():  # pylint: disable=invalid-name
  """Returns `True` if v2 control flow is enabled.

  Note: v2 control flow is always enabled inside of tf.function.
  """
  return control_flow_util.EnableControlFlowV2(ops.get_default_graph())