[jira] Resolved: (MAHOUT-557) Bug in Auc computation

["Ted Dunning (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAHOUT-557?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ted Dunning resolved MAHOUT-557.
--------------------------------

    Resolution: Fixed

Thanks to Anil for pointing out this oversight.

Fixed now with a test to match.


> Bug in Auc computation
> ----------------------
>
>                 Key: MAHOUT-557
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-557
>             Project: Mahout
>          Issue Type: Bug
>          Components: Classification
>    Affects Versions: 0.4
>            Reporter: Ted Dunning
>             Fix For: 0.5
>
>
> From Anil:
> Another bug: in Auc.java
> Classifier Evaluation :
> when the scores are tied -
> ...
> {quote}
>        // how many negatives are tied?
>        int k0 = 0;
>        while (i0 < n0 && v0 == tieScore) {
>          k0++;
>          i0++;
>          v0 = scores[0].get(i0);
>        }
>        // and how many positives
>        int k1 = 0;
>        while (i1 < n1 && v1 == tieScore) {
>          k1++;
>          i1++;
>          v1 = scores[1].get(i1);
>        }
> {quote}
> It sometimes goes Index out of bounds: Increment operation should be after accessing it
> {quote}
>  while (i0 < n0 && v0 == tieScore) {
>          v0 = scores[0].get(i0);
>          k0++;
>          i0++;
>        }
>        // and how many positives
>        int k1 = 0;
>        while (i1 < n1 && v1 == tieScore) {
>          v1 = scores[1].get(i1);
>          k1++;
>          i1++;
>        }
> {quote}
> Verily, he speaks truth.

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