title: colocate_gradients_with_ops argument in TensorFlow?
body: <p>I'm trying to understand what this argument does, the <a href="https://www.tensorflow.org/versions/r1.0/api_docs/python/tf/train/AdamOptimizer#compute_gradients" rel="nofollow noreferrer">TF api docs</a> for AdamOptimizer's <code>compute_gradients</code> method say the following -</p>
  
  <p><code>colocate_gradients_with_ops</code>: If True, try colocating gradients with the corresponding op.</p>
  
  <p>but it is not clear to me. What does colocating gradients mean in this context and what is the said op?</p>