You're in the middle of a saddle shape (see the figure [1]). This is bad because you could be lower (the goal is to be at the lowest point). Moreover, getting o

You're in the middle of a saddle shape (see the figure [1]). This is bad because you could be lower (the goal is to be at the lowest point). Moreover, getting out is apparently slow / difficult. The authors explain "how to escape" the saddle point in an efficient way. [1]: http://bair.berkeley.edu/blog/assets/saddle_eff/strictsaddle.png http://bair.berkeley.edu/blog/assets/saddle_eff/strictsaddle...