title: How TensorArray and while_loop work together in tensorflow?
body: <p>I am trying to produce a very easy example for combination of TensorArray and while_loop:</p>
  
  <pre><code># 1000 sequence in the length of 100
  matrix = tf.placeholder(tf.int32, shape=(100, 1000), name="input_matrix")
  matrix_rows = tf.shape(matrix)[0]
  ta = tf.TensorArray(tf.float32, size=matrix_rows)
  ta = ta.unstack(matrix)
  
  init_state = (0, ta)
  condition = lambda i, _: i &lt; n
  body = lambda i, ta: (i + 1, ta.write(i,ta.read(i)*2))
  
  # run the graph
  with tf.Session() as sess:
      (n, ta_final) = sess.run(tf.while_loop(condition, body, init_state),feed_dict={matrix: tf.ones(tf.float32, shape=(100,1000))})
      print (ta_final.stack())
  </code></pre>
  
  <p>But I am getting the following error:</p>
  
  <pre><code>ValueError: Tensor("while/LoopCond:0", shape=(), dtype=bool) must be from the same graph as Tensor("Merge:0", shape=(), dtype=float32).
  </code></pre>
  
  <p>Anyone has on idea what is the problem?</p>