09/05/2020
👉Interior Point (IP) methods: IP methods
cast the SVM learning task as a quadratic optimization problem subject to linear constraints.
The constraints are replaced with a barrier function. The result is a sequence of unconstrained problems which can be optimized very efficiently using Newton or Quasi-Newton
methods.
👉Decomposition methods: To overcome the quadratic memory requirement of IP methods,
decomposition methods such as SMO and SVM-Light tackle the dual representation of the SVM optimization problem, and employ an active set of constraints thus workingon a subset of dual variables. In the extreme case, called row-action methods, the activeset consists of a single constraint.
👉Primal optimization: Tackling the
primal objective directly was studied, for example, by Chapelle , who considered using smooth loss functions instead of the hinge loss, in which case the optimization problem
becomes a smooth unconstrained optimization problem. Chapelle then suggested using various optimization approaches such as conjugate gradient descent and Newton’s method. We
take a similar approach here, however we cope with the non-differentiability of the hingeloss directly by using sub-gradients instead of gradients.
Now in next post we'll look into codes and kernels.
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For pegasos, you can read this research paper :
https://www.google.com/url?sa=t&source=web&rct=j&url=https://ttic.uchicago.edu/~nati/Publications/PegasosMPB.pdf&ved=2ahUKEwjny5q586XpAhUr7HMBHTygCO8QFjACegQIAhAB&usg=AOvVaw0NEf9uKZVjxKtrCE7y5KfR
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