Ilya Sutskever：神经网络的目标函数是一种极其复杂的函数。它具有高度的非凸性（non-convex），并且丝毫没有能保证其优化过程必定会成功的数学依据。因此，如果你去和一位从理论角度研究优化的专家交谈，他们会告诉你，没有任何理论上的理由能让人相信这个优化过程会成功。然而，它就是成功了，这是一个经验性事实。 （2015年）
The neural network objective function is a very complicated objective function. It's very non convex, and there are no mathematical guarantees whatsoever about its success. And so if you were to speak to somebody who studies optimization from a theoretical point of view, they would tell you that there is no theoretical reason to believe that the optimization will succeed. And yet it does. And this is an empirical fact.
