From 96d92a1ffb6de1687849dd3895d6d13783404db0 Mon Sep 17 00:00:00 2001
From: "A. Unique TensorFlower" <gardener@tensorflow.org>
Date: Thu, 28 Jun 2018 11:39:35 -0700
Subject: Replace Keras clip by value and clip by norm in Keras Optimizers with
 native TF clip_ops, also added user input check for clipnorm and clipvalue >=
 0 if set

PiperOrigin-RevId: 202516320
---
 tensorflow/python/keras/optimizers.py      | 53 +++++++-----------------------
 tensorflow/python/keras/optimizers_test.py |  6 ++++
 2 files changed, 17 insertions(+), 42 deletions(-)

diff --git a/tensorflow/python/keras/optimizers.py b/tensorflow/python/keras/optimizers.py
index 34951791b5..b02cafcf61 100644
--- a/tensorflow/python/keras/optimizers.py
+++ b/tensorflow/python/keras/optimizers.py
@@ -19,17 +19,13 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
-import copy
-
 import six
 from six.moves import zip  # pylint: disable=redefined-builtin
 
-from tensorflow.python.framework import dtypes as dtypes_module
-from tensorflow.python.framework import ops
 from tensorflow.python.keras import backend as K
 from tensorflow.python.keras.utils.generic_utils import deserialize_keras_object
 from tensorflow.python.keras.utils.generic_utils import serialize_keras_object
-from tensorflow.python.ops import control_flow_ops
+from tensorflow.python.ops import clip_ops
 from tensorflow.python.ops import math_ops
 from tensorflow.python.ops import state_ops
 from tensorflow.python.training import distribute as distribute_lib
@@ -39,37 +35,6 @@ from tensorflow.python.training.checkpointable import tracking as checkpointable
 from tensorflow.python.util.tf_export import tf_export
 
 
-def clip_norm(g, c, n):
-  """Clip a tensor by norm.
-
-  Arguments:
-    g: gradient tensor to clip.
-    c: clipping threshold.
-    n: norm of gradient tensor.
-
-  Returns:
-    Clipped gradient tensor.
-  """
-  if c > 0:
-    condition = n >= c
-    then_expression = lambda: math_ops.scalar_mul(c / n, g)
-    else_expression = lambda: g
-
-    # saving the shape to avoid converting sparse tensor to dense
-    if isinstance(g, ops.Tensor):
-      g_shape = copy.copy(g.get_shape())
-    elif isinstance(g, ops.IndexedSlices):
-      g_shape = copy.copy(g.dense_shape)
-    if condition.dtype != dtypes_module.bool:
-      condition = math_ops.cast(condition, 'bool')
-    g = control_flow_ops.cond(condition, then_expression, else_expression)
-    if isinstance(g, ops.Tensor):
-      g.set_shape(g_shape)
-    elif isinstance(g, ops.IndexedSlices):
-      g._dense_shape = g_shape  # pylint: disable=protected-access
-  return g
-
-
 @tf_export('keras.optimizers.Optimizer')
 class Optimizer(object):
   """Abstract optimizer base class.
@@ -91,6 +56,9 @@ class Optimizer(object):
       if k not in allowed_kwargs:
         raise TypeError('Unexpected keyword argument '
                         'passed to optimizer: ' + str(k))
+      # checks that clipnorm >= 0 and clipvalue >= 0
+      if kwargs[k] < 0:
+        raise ValueError('Expected {} >= 0, received: {}'.format(k, kwargs[k]))
     self.__dict__.update(kwargs)
     self.updates = []
     self.weights = []
@@ -119,12 +87,13 @@ class Optimizer(object):
                        'gradient defined (i.e. are differentiable). '
                        'Common ops without gradient: '
                        'K.argmax, K.round, K.eval.')
-    if hasattr(self, 'clipnorm') and self.clipnorm > 0:
-      norm = K.sqrt(
-          sum([math_ops.reduce_sum(math_ops.square(g)) for g in grads]))
-      grads = [clip_norm(g, self.clipnorm, norm) for g in grads]
-    if hasattr(self, 'clipvalue') and self.clipvalue > 0:
-      grads = [K.clip(g, -self.clipvalue, self.clipvalue) for g in grads]
+    if hasattr(self, 'clipnorm'):
+      grads = [clip_ops.clip_by_norm(g, self.clipnorm) for g in grads]
+    if hasattr(self, 'clipvalue'):
+      grads = [
+          clip_ops.clip_by_value(g, -self.clipvalue, self.clipvalue)
+          for g in grads
+      ]
     return grads
 
   def set_weights(self, weights):
diff --git a/tensorflow/python/keras/optimizers_test.py b/tensorflow/python/keras/optimizers_test.py
index 92b0cf3261..55fc3fdcf4 100644
--- a/tensorflow/python/keras/optimizers_test.py
+++ b/tensorflow/python/keras/optimizers_test.py
@@ -145,6 +145,12 @@ class KerasOptimizersTest(test.TestCase):
     with self.assertRaises(NotImplementedError):
       optimizer.from_config(None)
 
+  def test_negative_clipvalue_or_clipnorm(self):
+    with self.assertRaises(ValueError):
+      _ = keras.optimizers.SGD(lr=0.01, clipvalue=-0.5)
+    with self.assertRaises(ValueError):
+      _ = keras.optimizers.Adam(clipnorm=-2.0)
+
 
 if __name__ == '__main__':
   test.main()
-- 
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