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https://issues.apache.org/jira/browse/SYSTEMML-2073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16326748#comment-16326748
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Matthias Boehm commented on SYSTEMML-2073:
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Related to this bug, we should also improve the performance of nrow and similar
meta data operations because this operation should not be slower than mvvar.
> Lost update on high frequency statistics maintenance
> ----------------------------------------------------
>
> Key: SYSTEMML-2073
> URL: https://issues.apache.org/jira/browse/SYSTEMML-2073
> Project: SystemML
> Issue Type: Bug
> Reporter: Matthias Boehm
> Priority: Major
>
> The recently introduced lock-free statistics maintenance (SYSTEMML-2069) has
> an issue of lost updates under high-frequency updates of hot opcodes. For
> example, the following script
> {code}
> parfor(j in 1:24)
> for(i in 1:10000000)
> q = nrow(Y);
> {code}
>
> gives the following statistics (counts of 240,000,000 are expected here)
> {code}
> # Instruction Time(s) Count
> 1 nrow 95.118 239999993
> 2 mvvar 64.423 239999957
> {code}
>
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