Add an experimental API to control behavior of outputting all intermediates when using v2 control flow inside Keras models in graph.

PiperOrigin-RevId: 261394829

tensorflow/core/graph/graph_constructor.cc

@@ -1180,10 +1180,19 @@ Status GraphConstructor::Convert() {
       }
 
       if (src_node != nullptr && src_index >= src_node->num_outputs()) {
-        return errors::InvalidArgument(
-            "Node '", node_def.name(), "': Connecting to invalid output ",
-            tensor_id.index(), " of source node ", tensor_id.node(),
-            " which has ", src_node->num_outputs(), " outputs");
+        std::ostringstream out;
+        out << "Node '" << node_def.name() << "': Connecting to invalid output "
+            << tensor_id.index() << " of source node " << tensor_id.node()
+            << " which has " << src_node->num_outputs() << " outputs.";
+
+        if (src_node->type_string() == "If" ||
+            src_node->type_string() == "StatelessIf" ||
+            src_node->type_string() == "While" ||
+            src_node->type_string() == "StatelessWhile") {
+          out << " Try using "
+              << "tf.compat.v1.experimental.output_all_intermediates(True).";
+        }
+        return errors::InvalidArgument(out.str());
       }
 
       inputs.emplace_back(string(tensor_id.node()), src_node, src_index);

tensorflow/python/BUILD

@@ -2591,11 +2591,24 @@ py_library(
     srcs_version = "PY2AND3",
     deps = [
         ":control_flow_util",
+        ":control_flow_util_v2",
         ":framework_ops",
         ":util",
     ],
 )
 
+tf_py_test(
+    name = "control_flow_v2_toggles_test",
+    size = "small",
+    srcs = ["ops/control_flow_v2_toggles_test.py"],
+    additional_deps = [
+        ":control_flow_v2_toggles",
+        ":control_flow_util_v2",
+        ":client_testlib",
+        ":platform_test",
+    ],
+)
+
 py_library(
     name = "cond_v2",
     srcs = [

tensorflow/python/kernel_tests/control_flow_ops_py_test.py

@@ -1007,6 +1007,31 @@ class ControlFlowTest(test.TestCase, parameterized.TestCase):
       grad = gradients_impl.gradients(r, [x])[0]
       self.assertAllEqual(1.0, self.evaluate(grad))
 
+  @test_util.run_deprecated_v1
+  @test_util.enable_control_flow_v2
+  def testCondComputeGradAfterSessRunFails(self):
+    with self.cached_session():
+      x = constant_op.constant(10.0, name="x")
+      pred = math_ops.less(1, 2)
+
+      def true_fn():
+        a = x * x
+        return a * a
+
+      def false_fn():
+        return x * x
+
+      r = control_flow_ops.cond(pred, true_fn, false_fn)
+
+      self.assertAllEqual(r, 10000.)
+      grad = gradients_impl.gradients(r, [x])[0]
+      with self.assertRaisesRegexp(
+          errors_impl.InvalidArgumentError,
+          r"Connecting to invalid output 1 of source node cond which has 1 "
+          r"outputs. Try using "
+          "tf.compat.v1.experimental.output_all_intermediates\(True\)."):
+        self.evaluate(grad)
+
   @test_util.run_deprecated_v1
   @test_util.enable_output_all_intermediates
   def testCondComputeGradAfterSessRun(self):

tensorflow/python/ops/control_flow_v2_toggles.py

@@ -21,6 +21,7 @@ from __future__ import print_function
 
 from tensorflow.python.framework import ops
 from tensorflow.python.ops import control_flow_util
+from tensorflow.python.ops import control_flow_util_v2
 from tensorflow.python.util.tf_export import tf_export
 
 
@@ -64,3 +65,30 @@ def control_flow_v2_enabled():  # pylint: disable=invalid-name
   Note: v2 control flow is always enabled inside of tf.function.
   """
   return control_flow_util.EnableControlFlowV2(ops.get_default_graph())
+
+
+@tf_export(v1=["experimental.output_all_intermediates"])
+def output_all_intermediates(state):  # pylint: disable=invalid-name
+  """Whether to output all intermediates from functional control flow ops.
+
+  The "default" behavior to is to output all intermediates when using v2 control
+  flow inside Keras models in graph mode (possibly inside Estimators). This is
+  needed to support taking gradients of v2 control flow. In graph mode, Keras
+  can sometimes freeze the forward graph before the gradient computation which
+  does not work for v2 control flow since it requires updating the forward ops
+  to output the needed intermediates. We work around this by proactively
+  outputting the needed intermediates when building the forward pass itself.
+  Ideally any such extra tensors should be pruned out at runtime. However, if
+  for any reason this doesn't work for you or if you have an infernce-only model
+  you can turn this behavior off using
+  `tf.compat.v1.experimental.output_all_intermediates(False)`.
+
+  If with the default behavior you are still seeing errors of the form
+  "Connecting to invalid output X of source node Y which has Z outputs" try
+  setting `tf.compat.v1.experimental.output_all_intermediates(True)` and
+  please file an issue at https://github.com/tensorflow/tensorflow/issues.
+
+  Args:
+    state: True, False or None. None restores the default behavior.
+  """
+  control_flow_util_v2._EXPERIMENTAL_OUTPUT_ALL_INTERMEDIATES_OVERRIDE = state  # pylint: disable=protected-access

tensorflow/python/ops/control_flow_v2_toggles_test.py

@@ -0,0 +1,44 @@
+# 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
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Tests for control_flow_v2_toggles.py."""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from tensorflow.python.ops import control_flow_util_v2
+from tensorflow.python.ops import control_flow_v2_toggles
+from tensorflow.python.platform import googletest
+from tensorflow.python.platform import test
+
+
+class ControlFlowV2TogglesTest(test.TestCase):
+
+  def testOutputAllIntermediates(self):
+    self.assertIsNone(
+        control_flow_util_v2._EXPERIMENTAL_OUTPUT_ALL_INTERMEDIATES_OVERRIDE)
+    control_flow_v2_toggles.output_all_intermediates(True)
+    self.assertTrue(
+        control_flow_util_v2._EXPERIMENTAL_OUTPUT_ALL_INTERMEDIATES_OVERRIDE)
+    control_flow_v2_toggles.output_all_intermediates(False)
+    self.assertFalse(
+        control_flow_util_v2._EXPERIMENTAL_OUTPUT_ALL_INTERMEDIATES_OVERRIDE)
+    control_flow_v2_toggles.output_all_intermediates(None)
+    self.assertIsNone(
+        control_flow_util_v2._EXPERIMENTAL_OUTPUT_ALL_INTERMEDIATES_OVERRIDE)
+
+
+if __name__ == '__main__':
+  googletest.main()

tensorflow/tools/api/golden/v1/tensorflow.experimental.pbtxt

@@ -4,4 +4,8 @@ tf_module {
     name: "function_executor_type"
     argspec: "args=[\'executor_type\'], varargs=None, keywords=None, defaults=None"
   }
+  member_method {
+    name: "output_all_intermediates"
+    argspec: "args=[\'state\'], varargs=None, keywords=None, defaults=None"
+  }
 }

tensorflow/tools/compatibility/renames_v2.py

@@ -363,6 +363,8 @@ renames = {
         'tf.compat.v1.estimator.tpu.TPUEstimatorSpec',
     'tf.estimator.tpu.experimental.EmbeddingSpec':
         'tf.compat.v1.estimator.tpu.experimental.EmbeddingSpec',
+    'tf.experimental.output_all_intermediates':
+        'tf.compat.v1.experimental.output_all_intermediates',
     'tf.expm1':
         'tf.math.expm1',
     'tf.fake_quant_with_min_max_args':