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https://issues.apache.org/jira/browse/SYSTEMML-1644?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matthias Boehm updated SYSTEMML-1644:
-------------------------------------
Description:
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.
was:
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}
> Incorrect results on multi-threaded dense-dense matrix multiply w/ wide rhs
> ---------------------------------------------------------------------------
>
> Key: SYSTEMML-1644
> URL: https://issues.apache.org/jira/browse/SYSTEMML-1644
> Project: SystemML
> Issue Type: Bug
> Reporter: 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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