title: Tensorflow Copy Weights Issue
body: <p>I am using Tensorflow 0.8 to train the Deep Neural Networks. Currently, I encounter an issue that I want to define two exact same Neural Networks N1 and N2, and I train N1, during the training loop, I copy updated weights from N1 to N2 every 4 iterations. In fact, I know there is way using <code>tf.train.saver.save()</code> to save all N1 weights into a <code>.ckpt</code> file on Disk, and using <code>tf.train.saver.restore()</code> to load those weights from .ckpt file, which is equivalent to the copy functionality. However, this load/reload will impact the training speed, and I wonder if there are other more efficient ways to do the copy (For example, do in-memory copy, etc.). Thanks!</p>