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From "Matthias Boehm (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (SYSTEMML-1644) Incorrect results on multi-threaded dense-dense matrix multiply w/ short lhs
Date Mon, 29 May 2017 23:17:04 GMT

     [ https://issues.apache.org/jira/browse/SYSTEMML-1644?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Matthias Boehm reassigned SYSTEMML-1644:
----------------------------------------

    Assignee: Matthias Boehm

> Incorrect results on multi-threaded dense-dense matrix multiply w/ short lhs
> ----------------------------------------------------------------------------
>
>                 Key: SYSTEMML-1644
>                 URL: https://issues.apache.org/jira/browse/SYSTEMML-1644
>             Project: SystemML
>          Issue Type: Bug
>            Reporter: Matthias Boehm
>            Assignee: Matthias Boehm
>
> The following matrix multiply expression yields incorrect results compared to R when
run with multi-threaded operations but correct results with single-threaded operations.
> {code}
> # X is dense 2023 x 1987 matrix
> # t(U) is dense 10 x  2023 matrix
> R = t(U) %*% X;
> {code}
> Note: This affects any dense-dense matrix multiplication with short left-hand-side (of
<=16 rows) and wide right-hand-side (of #features > the cache block size of 1024 columns).
Such operations occur for example in Mlogreg and Kmeans with a number of classes/centroids
1 < x <= 16 and a feature matrix with ncol(X) > 1024.



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