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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-248) Multiplying sparse matrices is slow
Date Sun, 22 Feb 2009 20:37:02 GMT

    [ https://issues.apache.org/jira/browse/MATH-248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12675704#action_12675704
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Luc Maisonobe commented on MATH-248:
------------------------------------

You are right. It is probably even worse when compared to DenseRealMatrix which should be
more cache-friendly than RealMatrixImpl.

It is also possible to walk through non-zero elements of both matrices.

Could you provide a patch for this ?

> Multiplying sparse matrices is slow
> -----------------------------------
>
>                 Key: MATH-248
>                 URL: https://issues.apache.org/jira/browse/MATH-248
>             Project: Commons Math
>          Issue Type: Improvement
>            Reporter: Christian Semrau
>            Priority: Minor
>
> The multiplication of sparse real matrices is very slow compared to real matrices: Ten
times as slow for size 200, four times as slow for size 400. The time is independent of the
number of nonzero entries, because the general algorithm inherited from AbstractRealMatrix
is used. I suggest using a specialized multiplication algorithm for matrices that are "sparse
enough", walking only over the nonzero entries in one of the matrices.

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