1# Copyright 2019 The TensorFlow Authors. All Rights Reserved. 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); 4# you may not use this file except in compliance with the License. 5# You may obtain a copy of the License at 6# 7# http://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, 11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12# See the License for the specific language governing permissions and 13# limitations under the License. 14# ============================================================================== 15 16"""API for enabling v2 control flow.""" 17 18from __future__ import absolute_import 19from __future__ import division 20from __future__ import print_function 21 22from tensorflow.python.framework import ops 23from tensorflow.python.ops import control_flow_util 24from tensorflow.python.ops import control_flow_util_v2 25from tensorflow.python.util.tf_export import tf_export 26 27 28@tf_export(v1=["enable_control_flow_v2"]) 29def enable_control_flow_v2(): # pylint: disable=invalid-name 30 """Use control flow v2. 31 32 control flow v2 (cfv2) is an improved version of control flow in TensorFlow 33 with support for higher order derivatives. Enabling cfv2 will change the 34 graph/function representation of control flow, e.g., `tf.while_loop` and 35 `tf.cond` will generate functional `While` and `If` ops instead of low-level 36 `Switch`, `Merge` etc. ops. Note: Importing and running graphs exported 37 with old control flow will still be supported. 38 39 Calling tf.enable_control_flow_v2() lets you opt-in to this TensorFlow 2.0 40 feature. 41 42 Note: v2 control flow is always enabled inside of tf.function. Calling this 43 function is not required. 44 """ 45 # pylint: disable=protected-access 46 ops._control_flow_api_gauge.get_cell().set(True) 47 control_flow_util.ENABLE_CONTROL_FLOW_V2 = True 48 49 50@tf_export(v1=["disable_control_flow_v2"]) 51def disable_control_flow_v2(): # pylint: disable=invalid-name 52 """Opts out of control flow v2. 53 54 Note: v2 control flow is always enabled inside of tf.function. Calling this 55 function has no effect in that case. 56 57 If your code needs tf.disable_control_flow_v2() to be called to work 58 properly please file a bug. 59 """ 60 # pylint: disable=protected-access 61 ops._control_flow_api_gauge.get_cell().set(False) 62 control_flow_util.ENABLE_CONTROL_FLOW_V2 = False 63 64 65@tf_export(v1=["control_flow_v2_enabled"]) 66def control_flow_v2_enabled(): # pylint: disable=invalid-name 67 """Returns `True` if v2 control flow is enabled. 68 69 Note: v2 control flow is always enabled inside of tf.function. 70 """ 71 return control_flow_util.EnableControlFlowV2(ops.get_default_graph()) 72 73 74@tf_export(v1=["experimental.output_all_intermediates"]) 75def output_all_intermediates(state): # pylint: disable=invalid-name 76 """Whether to output all intermediates from functional control flow ops. 77 78 The "default" behavior to is to output all intermediates when using v2 control 79 flow inside Keras models in graph mode (possibly inside Estimators). This is 80 needed to support taking gradients of v2 control flow. In graph mode, Keras 81 can sometimes freeze the forward graph before the gradient computation which 82 does not work for v2 control flow since it requires updating the forward ops 83 to output the needed intermediates. We work around this by proactively 84 outputting the needed intermediates when building the forward pass itself. 85 Ideally any such extra tensors should be pruned out at runtime. However, if 86 for any reason this doesn't work for you or if you have an inference-only 87 model you can turn this behavior off using 88 `tf.compat.v1.experimental.output_all_intermediates(False)`. 89 90 If with the default behavior you are still seeing errors of the form 91 "Connecting to invalid output X of source node Y which has Z outputs" try 92 setting `tf.compat.v1.experimental.output_all_intermediates(True)` and 93 please file an issue at https://github.com/tensorflow/tensorflow/issues. 94 95 Args: 96 state: True, False or None. None restores the default behavior. 97 """ 98 control_flow_util_v2._EXPERIMENTAL_OUTPUT_ALL_INTERMEDIATES_OVERRIDE = state # pylint: disable=protected-access 99