A local minimum is a point whose objective value is no greater than nearby points, even if a lower value exists elsewhere. This differs from the global optimum that convex optimization can guarantee for SVMs. section 2.0
Early doubts about neural-network training treated local minima as inevitable traps for gradient methods. AlexNet challenged that view: high-dimensional loss surfaces differ from simple terrain, and mini-batch gradients can smooth irregularities and support more stable optimization. section 2.5.4








