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Old 02-22-2013, 04:17 PM
ilya239 ilya239 is offline
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Join Date: Jul 2012
Posts: 58
Default Re: Odd results using LibSVM on Prob 8

I'm using a different package (python and cvxopt), but had the same issue (some points would occasionally be misclassified). Turned out to be a bug in my code, in the way I was computing b once the \alpha have been returned from the quadratic programming call.

Try checking whether the returned solution satisfies the constraints, and whether it is at least a local minimum (small changes in \alpha lead to small increases in \cal L(\alpha). Also, that all but a few of the \alpha_i are near-zero. If all that is true, the error is downstream from there, else upstream.
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