Re: Why not use soft margin SVM everytime?
The remark about using hardmargin SVM in nonseparable cases was not a recommendation. It was to point out that if you use hardmargin SVM and the data turns out to be nonseparable after all, this can be easily detected by checking the solution (if QP returns one) on the training data points. This relieves you from the need to determine linear separability before you apply hardmargin SVM. You can of course use softmargin SVM in all cases.
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