How can I compute the gradient w.r.t. a non-variable in TensorFlow's eager execution mode?












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I am trying to compute the gradient of my model's loss with respect to its input in order to create an adversarial example. Since the model's input is non-trainable, I need to compute the gradient with respect to a tensor, not a variable. However, I found that TensorFlow's GradientTape returns None gradients if the tensor is not a trainable variable:



import numpy as np
import tensorflow as tf

tf.enable_eager_execution()

a = tf.convert_to_tensor(np.array([1., 2., 3.]), dtype=tf.float32)
b = tf.constant([1., 2., 3.])
c = tf.Variable([1., 2., 3.], trainable=False)
d = tf.Variable([1., 2., 3.], trainable=True)

with tf.GradientTape() as tape:
result = a + b + c + d

grads = tape.gradient(result, [a, b, c, d])


print(grads) prints:



[None, None, None, <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]


I went through TensorFlow's Eager Execution tutorial and the Eager Execution guide, but couldn't find a solution for calculating the gradient w.r.t. a tensor.










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    0















    I am trying to compute the gradient of my model's loss with respect to its input in order to create an adversarial example. Since the model's input is non-trainable, I need to compute the gradient with respect to a tensor, not a variable. However, I found that TensorFlow's GradientTape returns None gradients if the tensor is not a trainable variable:



    import numpy as np
    import tensorflow as tf

    tf.enable_eager_execution()

    a = tf.convert_to_tensor(np.array([1., 2., 3.]), dtype=tf.float32)
    b = tf.constant([1., 2., 3.])
    c = tf.Variable([1., 2., 3.], trainable=False)
    d = tf.Variable([1., 2., 3.], trainable=True)

    with tf.GradientTape() as tape:
    result = a + b + c + d

    grads = tape.gradient(result, [a, b, c, d])


    print(grads) prints:



    [None, None, None, <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]


    I went through TensorFlow's Eager Execution tutorial and the Eager Execution guide, but couldn't find a solution for calculating the gradient w.r.t. a tensor.










    share|improve this question

























      0












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      0








      I am trying to compute the gradient of my model's loss with respect to its input in order to create an adversarial example. Since the model's input is non-trainable, I need to compute the gradient with respect to a tensor, not a variable. However, I found that TensorFlow's GradientTape returns None gradients if the tensor is not a trainable variable:



      import numpy as np
      import tensorflow as tf

      tf.enable_eager_execution()

      a = tf.convert_to_tensor(np.array([1., 2., 3.]), dtype=tf.float32)
      b = tf.constant([1., 2., 3.])
      c = tf.Variable([1., 2., 3.], trainable=False)
      d = tf.Variable([1., 2., 3.], trainable=True)

      with tf.GradientTape() as tape:
      result = a + b + c + d

      grads = tape.gradient(result, [a, b, c, d])


      print(grads) prints:



      [None, None, None, <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]


      I went through TensorFlow's Eager Execution tutorial and the Eager Execution guide, but couldn't find a solution for calculating the gradient w.r.t. a tensor.










      share|improve this question














      I am trying to compute the gradient of my model's loss with respect to its input in order to create an adversarial example. Since the model's input is non-trainable, I need to compute the gradient with respect to a tensor, not a variable. However, I found that TensorFlow's GradientTape returns None gradients if the tensor is not a trainable variable:



      import numpy as np
      import tensorflow as tf

      tf.enable_eager_execution()

      a = tf.convert_to_tensor(np.array([1., 2., 3.]), dtype=tf.float32)
      b = tf.constant([1., 2., 3.])
      c = tf.Variable([1., 2., 3.], trainable=False)
      d = tf.Variable([1., 2., 3.], trainable=True)

      with tf.GradientTape() as tape:
      result = a + b + c + d

      grads = tape.gradient(result, [a, b, c, d])


      print(grads) prints:



      [None, None, None, <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]


      I went through TensorFlow's Eager Execution tutorial and the Eager Execution guide, but couldn't find a solution for calculating the gradient w.r.t. a tensor.







      python tensorflow






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      asked Nov 19 '18 at 22:27









      Kilian BatznerKilian Batzner

      2,42311832




      2,42311832
























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          The tf.GradientTape documentation reveals the simple solution:




          Trainable variables (created by tf.Variable or tf.get_variable, where trainable=True is default in both cases) are automatically watched. Tensors can be manually watched by invoking the watch method on this context manager.




          In this case,



          with tf.GradientTape() as tape:
          tape.watch(a)
          tape.watch(b)
          tape.watch(c)
          result = a + b + c + d

          grads = tape.gradient(result, [a, b, c, d])


          will result in print(grads):



          [<tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>, 
          <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
          <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
          <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]





          share|improve this answer























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            1 Answer
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            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

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            active

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            active

            oldest

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            0














            The tf.GradientTape documentation reveals the simple solution:




            Trainable variables (created by tf.Variable or tf.get_variable, where trainable=True is default in both cases) are automatically watched. Tensors can be manually watched by invoking the watch method on this context manager.




            In this case,



            with tf.GradientTape() as tape:
            tape.watch(a)
            tape.watch(b)
            tape.watch(c)
            result = a + b + c + d

            grads = tape.gradient(result, [a, b, c, d])


            will result in print(grads):



            [<tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>, 
            <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
            <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
            <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]





            share|improve this answer




























              0














              The tf.GradientTape documentation reveals the simple solution:




              Trainable variables (created by tf.Variable or tf.get_variable, where trainable=True is default in both cases) are automatically watched. Tensors can be manually watched by invoking the watch method on this context manager.




              In this case,



              with tf.GradientTape() as tape:
              tape.watch(a)
              tape.watch(b)
              tape.watch(c)
              result = a + b + c + d

              grads = tape.gradient(result, [a, b, c, d])


              will result in print(grads):



              [<tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>, 
              <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
              <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
              <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]





              share|improve this answer


























                0












                0








                0







                The tf.GradientTape documentation reveals the simple solution:




                Trainable variables (created by tf.Variable or tf.get_variable, where trainable=True is default in both cases) are automatically watched. Tensors can be manually watched by invoking the watch method on this context manager.




                In this case,



                with tf.GradientTape() as tape:
                tape.watch(a)
                tape.watch(b)
                tape.watch(c)
                result = a + b + c + d

                grads = tape.gradient(result, [a, b, c, d])


                will result in print(grads):



                [<tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>, 
                <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
                <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
                <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]





                share|improve this answer













                The tf.GradientTape documentation reveals the simple solution:




                Trainable variables (created by tf.Variable or tf.get_variable, where trainable=True is default in both cases) are automatically watched. Tensors can be manually watched by invoking the watch method on this context manager.




                In this case,



                with tf.GradientTape() as tape:
                tape.watch(a)
                tape.watch(b)
                tape.watch(c)
                result = a + b + c + d

                grads = tape.gradient(result, [a, b, c, d])


                will result in print(grads):



                [<tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>, 
                <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
                <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>,
                <tf.Tensor: id=26, shape=(3,), dtype=float32, numpy=array([1., 1., 1.], dtype=float32)>]






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Nov 19 '18 at 22:27









                Kilian BatznerKilian Batzner

                2,42311832




                2,42311832






























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