tensorflow while_loop: ValueError: None values not supported

Question

I'm trying to use slice a tensor object in my graph. Code is as follows:

        utt_inputs = []
        idx = tf.zeros(shape=(), dtype=tf.int32)
        def add_inputs(idx):
            utt_input = tf.slice(last_outputs, begin=[idx, 0], size=[self.args.uttWindowSize, self.args.wordUnits])
            utt_inputs.append(utt_input)

        def my_cond(idx):
            idx = tf.add(idx, 1)
            return tf.less(idx, self.batchSize)

        tf.while_loop(cond=my_cond, body=add_inputs, loop_vars=[idx])

where self.batchSize is a placeholder of tf.int32. Last_outputs is a 2-d tensor. However, when I run the code, tensorflow gives an error:

Traceback (most recent call last):
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3\helpers\pydev\pydevd.py", line 1596, in <module>
    globals = debugger.run(setup['file'], None, None, is_module)
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3\helpers\pydev\pydevd.py", line 974, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "C:\Program Files (x86)\JetBrains\PyCharm 2016.3\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "C:/Users/v-zhaom/OneDrive/speakerRNN/main.py", line 5, in <module>
    speakerTagger.main()
  File "C:/Users/v-zhaom/OneDrive/speakerRNN\speakerChangeTagger\tagger.py", line 152, in main
    self.model = RecurrentModel(self.args, self.textData)
  File "C:/Users/v-zhaom/OneDrive/speakerRNN\speakerChangeTagger\RecurrentModel.py", line 29, in __init__
    self.buildNetWork()
  File "C:/Users/v-zhaom/OneDrive/speakerRNN\speakerChangeTagger\RecurrentModel.py", line 36, in buildNetWork
    context_vectors = self._buildUttNetwork(last_outputs)
  File "C:/Users/v-zhaom/OneDrive/speakerRNN\speakerChangeTagger\RecurrentModel.py", line 136, in _buildUttNetwork
    tf.while_loop(cond=my_cond, body=add_inputs, loop_vars=[idx])
  File "C:\Python35\lib\site-packages\tensorflow\python\ops\control_flow_ops.py", line 2636, in while_loop
    result = context.BuildLoop(cond, body, loop_vars, shape_invariants)
  File "C:\Python35\lib\site-packages\tensorflow\python\ops\control_flow_ops.py", line 2469, in BuildLoop
    pred, body, original_loop_vars, loop_vars, shape_invariants)
  File "C:\Python35\lib\site-packages\tensorflow\python\ops\control_flow_ops.py", line 2441, in _BuildLoop
    next_vars.append(_AddNextAndBackEdge(m, v))
  File "C:\Python35\lib\site-packages\tensorflow\python\ops\control_flow_ops.py", line 635, in _AddNextAndBackEdge
    v = ops.convert_to_tensor(v)
  File "C:\Python35\lib\site-packages\tensorflow\python\framework\ops.py", line 669, in convert_to_tensor
    ret = conversion_func(value, dtype=dtype, name=name, as_ref=as_ref)
  File "C:\Python35\lib\site-packages\tensorflow\python\framework\constant_op.py", line 176, in _constant_tensor_conversion_function
    return constant(v, dtype=dtype, name=name)
  File "C:\Python35\lib\site-packages\tensorflow\python\framework\constant_op.py", line 165, in constant
    tensor_util.make_tensor_proto(value, dtype=dtype, shape=shape, verify_shape=verify_shape))
  File "C:\Python35\lib\site-packages\tensorflow\python\framework\tensor_util.py", line 360, in make_tensor_proto
    raise ValueError("None values not supported.")
ValueError: None values not supported.

T-32 · Accepted Answer · 2018-02-14 12:16:36Z

1

The function passed to the body parameter should return a tensor value, not None. Try changing the function to the following.

def add_inputs(idx):
    utt_input = tf.slice(last_outputs, begin=[idx, 0],
    size=[self.args.uttWindowSize, self.args.wordUnits])
    utt_inputs.append(utt_input)
    return tf.constant(0 , dtype=tf.int32 , name="ret_val") #Dummy

From the docs,

body is a callable returning a (possibly nested) tuple, namedtuple or list of tensors of the same arity (length and structure) and types as loop_vars.

answered Feb 14, 2018 at 12:16

T-32

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