Add support for freezing the Exit and Enter op when it is used with resource variables.

PiperOrigin-RevId: 260570736

tensorflow/python/framework/graph_util_impl.py

@@ -45,6 +45,13 @@ _VARIABLE_OPS = {
     "VariableV2",
 }
 
+_CONTROL_FLOW_OP_NAMES_OR_IDENTITY = [
+    "Switch",
+    "Enter",
+    "Exit",
+    "Identity",
+]
+
 
 def _is_variable_op(op):
   """Returns true if 'op' refers to a Variable node."""
@@ -290,11 +297,12 @@ def convert_variables_to_constants(sess,
       else:
         variable_names.append(variable_name + ":0")
     elif node.op in ["ReadVariableOp", "ResourceGather"]:
-      # There can be one or more Identity or Switch ops in between the
+      # There can be one or more Identity or control flow ops in between the
       # ReadVariableOp and VarHandleOp. Store the ops with the associated
       # dtypes.
       source_op_name = get_input_name(node)
-      while map_name_to_node[source_op_name].op in ["Identity", "Switch"]:
+      while (map_name_to_node[source_op_name].op in
+             _CONTROL_FLOW_OP_NAMES_OR_IDENTITY):
         resource_op_types[source_op_name] = node.attr["dtype"]
         source_op_name = get_input_name(map_name_to_node[source_op_name])
       if map_name_to_node[source_op_name].op != "VarHandleOp":

tensorflow/python/framework/graph_util_test.py

@@ -327,6 +327,10 @@ class ConvertVariablesToConstantsTest(test.TestCase):
         sess.graph.get_tensor_by_name(tensor.name) for tensor in tensor_list
     ]
 
+  def _get_tensor_names(self, tensors):
+    """Returns a list of string names for the tensors specified."""
+    return [tensor.name.split(":")[0] for tensor in tensors]
+
   def _evaluate_graph_def(self, graph_def, inputs, outputs, input_data):
     """Evaluates the GraphDef using Sessions."""
     with ops.Graph().as_default() as graph:
@@ -338,6 +342,19 @@ class ConvertVariablesToConstantsTest(test.TestCase):
     return sess.run(
         output_tensors, feed_dict=dict(zip(input_tensors, input_data)))
 
+  def _ensure_no_variables_in_graph(self, graph_def):
+    """Ensures there are no variables in the graph."""
+    for node in graph_def.node:
+      self.assertNotIn(
+          node.op, ["Variable", "VariableV2", "VarHandleOp", "ReadVariableOp"])
+
+  def _test_converted_keras_model(self, model, constant_graph_def, input_data):
+    """Compares the converted Keras model."""
+    expected_value = model.predict(input_data)
+    actual_value = self._evaluate_graph_def(constant_graph_def, model.inputs,
+                                            model.outputs, [input_data])
+    np.testing.assert_almost_equal(np.array([expected_value]), actual_value, 5)
+
   def _test_variable_to_const_conversion(self, use_resource):
     with ops.Graph().as_default():
       with variable_scope.variable_scope("", use_resource=use_resource):
@@ -395,10 +412,7 @@ class ConvertVariablesToConstantsTest(test.TestCase):
     with ops.Graph().as_default():
       _ = importer.import_graph_def(constant_graph_def, name="")
       self.assertEqual(4, len(constant_graph_def.node))
-      for node in constant_graph_def.node:
-        self.assertNotIn(
-            node.op,
-            ["Variable", "VariableV2", "VarHandleOp", "ReadVariableOp"])
+      self._ensure_no_variables_in_graph(constant_graph_def)
       with session.Session() as sess:
         output_node = sess.graph.get_tensor_by_name("output_node:0")
         output = self.evaluate(output_node)
@@ -440,10 +454,7 @@ class ConvertVariablesToConstantsTest(test.TestCase):
         constant_graph_def = graph_util.convert_variables_to_constants(
             sess, variable_graph_def, ["output_node"])
 
-    # Ensure there are no variables after freezing.
-    for node in constant_graph_def.node:
-      self.assertNotIn(
-          node.op, ["Variable", "VariableV2", "VarHandleOp", "ReadVariableOp"])
+    self._ensure_no_variables_in_graph(constant_graph_def)
 
   def testReferenceVariables(self):
     """Freezes a graph with reference variables."""
@@ -464,9 +475,6 @@ class ConvertVariablesToConstantsTest(test.TestCase):
   @test_util.run_v1_only("Incompatible with TF 2.0")
   def testWithEmbeddings(self):
     """Freezes a graph with embeddings."""
-    input_data = np.array(np.random.random_sample([1, 1]), dtype=np.int32)
-
-    # Make model.
     state_input = keras.layers.Input(
         shape=(1,), name="state_input", dtype="int32")
     output = keras.layers.Embedding(
@@ -476,25 +484,19 @@ class ConvertVariablesToConstantsTest(test.TestCase):
     model.compile(
         loss={"state": "sparse_categorical_crossentropy"}, optimizer="adam")
 
-    # Get associated session.
+    # Freeze the graph.
     sess = keras.backend.get_session()
     variable_graph_def = sess.graph_def
-    output_tensor = [tensor.name.split(":")[0] for tensor in model.outputs]
+    output_tensor = self._get_tensor_names(model.outputs)
     constant_graph_def = graph_util.convert_variables_to_constants(
         sess, variable_graph_def, output_tensor)
 
-    # Ensure graph has no variables.
-    for node in constant_graph_def.node:
-      self.assertNotIn(
-          node.op, ["Variable", "VariableV2", "VarHandleOp", "ReadVariableOp"])
+    # Validate converted graph.
+    input_data = np.array(np.random.random_sample([1, 1]), dtype=np.int32)
+    self._ensure_no_variables_in_graph(constant_graph_def)
+    self._test_converted_keras_model(model, constant_graph_def, input_data)
 
-    # Compare the value of the graphs.
-    expected_value = model.predict(input_data)
-    actual_value = self._evaluate_graph_def(constant_graph_def, model.inputs,
-                                            model.outputs, [input_data])
-    np.testing.assert_almost_equal(np.array([expected_value]), actual_value, 5)
-
-  def testWithSwitch(self):
+  def testGraphWithSwitch(self):
     """Freezes a graph which contains a Switch with type RESOURCE_DT."""
     with ops.Graph().as_default():
       with variable_scope.variable_scope("", use_resource=True):
@@ -513,10 +515,25 @@ class ConvertVariablesToConstantsTest(test.TestCase):
           constant_graph_def = graph_util.convert_variables_to_constants(
               sess, variable_graph_def, ["output_node"])
 
-    # Ensure there are no variables after freezing.
-    for node in constant_graph_def.node:
-      self.assertNotIn(
-          node.op, ["Variable", "VariableV2", "VarHandleOp", "ReadVariableOp"])
+    self._ensure_no_variables_in_graph(constant_graph_def)
+
+  @test_util.run_v1_only("Incompatible with TF 2.0")
+  def testLSTM(self):
+    """Freezes a Keras LSTM."""
+    model = keras.models.Sequential(
+        [keras.layers.LSTM(units=10, input_shape=(10, 10))])
+
+    # Freeze the model.
+    sess = keras.backend.get_session()
+    variable_graph_def = sess.graph_def
+    output_tensor = self._get_tensor_names(model.outputs)
+    constant_graph_def = graph_util.convert_variables_to_constants(
+        sess, variable_graph_def, output_tensor)
+
+    # Validate converted graph.
+    input_data = np.array(np.random.random_sample([10, 10, 10]), dtype=np.int32)
+    self._ensure_no_variables_in_graph(constant_graph_def)
+    self._test_converted_keras_model(model, constant_graph_def, input_data)
 
 
 if __name__ == "__main__":