Deep-Learning Nan loss reasons

Question

Perhaps too general a question, but can anyone explain what would cause a Convolutional Neural Network to diverge?

Specifics:

I am using Tensorflow\'s iris_tra

Answer 1

If using integers as targets, makes sure they aren't symmetrical at 0.

I.e., don't use classes -1, 0, 1. Use instead 0, 1, 2.