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https://issues.apache.org/jira/browse/SPARK-20790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16014723#comment-16014723
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David Eis commented on SPARK-20790:
-----------------------------------
See
https://github.com/apache/spark/pull/5314/files#diff-be65dd1d6adc53138156641b610fcadaR1118
ls.add is only called if rating > 0, which is not what was done prior to the
commit, nor does it represent what is conveyed in the comment on the previous
line.
To reproduce, you can run with a ratings matrix with any negative values and it
will be identical to running with the same ratings matrix with the negative
values zeroed out.
> ALS with implicit feedback ignores negative values
> --------------------------------------------------
>
> Key: SPARK-20790
> URL: https://issues.apache.org/jira/browse/SPARK-20790
> Project: Spark
> Issue Type: Bug
> Components: ML, MLlib
> Affects Versions: 1.3.1, 1.4.0, 1.4.1, 1.5.0, 1.5.1, 1.5.2, 1.6.0, 1.6.1,
> 1.6.2, 1.6.3, 2.0.0, 2.0.1, 2.0.2, 2.1.0, 2.1.1
> Reporter: David Eis
>
> The refactorization that was done in
> https://github.com/apache/spark/pull/5314/files introduced a bug, whereby for
> implicit feedback negative ratings just get ignored. Prior to that commit
> they were not ignored, but the absolute value was used as the confidence and
> the preference was set to 0. The preservation of comments and absolute value
> indicate that this was unintentional.
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