Implement functions with saddle points in high dimensions

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How do we construct such functions? (references)

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Pascanu, Razvan, et al. "On the saddle point problem for non-convex optimization." arXiv preprint arXiv:1405.4604 (2014). and Dauphin, Yann N., et al. "Identifying and attacking the saddle point problem in high-dimensional non-convex optimization." Advances in neural information processing systems. 2014. might contain some relevant details.