How does one debug NaN values in TensorFlow?

Question

I was running TensorFlow and I happen to have something yielding a NaN. I\'d like to know what it is but I do not know how to do this. The main issue is that in a \"normal\"

Answer 1

First of all, you need to check you input data properly. In most cases this is the reason. But not always, of course.

I usually use Tensorboard to see whats happening while training. So you can see the values on each step with

Z = tf.pow(Z, 2.0)    
summary_z = tf.scalar_summary('z', Z) 
#etc..
summary_merge = tf.merge_all_summaries()
#on each desired step save: 
    summary_str = sess.run(summary_merge)
    summary_writer.add_summary(summary_str, i)

Also you can simply eval and print the current value:

 print(sess.run(Z))