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https://issues.apache.org/jira/browse/MAHOUT-1190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13628298#comment-13628298
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Robin Anil edited comment on MAHOUT-1190 at 4/10/13 9:42 PM:
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Please add a test case to VectorBenchmarks.java, Most of the code in Mahout are
tuned with RandomAccess and DenseVectors in mind. Sequential access is a slow
format. And really the lower memory requirements does not really justify its
existence. I've always wanted to delete that one from the codebase altogether.
Vector benchmarks tests a lot of combination of things. I wouldnt want other
formats to regress on performance.
was (Author: robinanil):
Please add a test case to VectorBenchmarks.java, Most of the code in Mahout
is runed for RandomAccess and DenseVectors in mind. Sequential access is a slow
format. And really the lower memory requirements does not really justify its
existence. I would have wanted to delete that one from the codebase altogether.
Vector benchmarks tests a lot of combination of things. I wouldnt want other
formats to regress on performance.
> SequentialAccessSparseVector function assignment is very slow
> -------------------------------------------------------------
>
> Key: MAHOUT-1190
> URL: https://issues.apache.org/jira/browse/MAHOUT-1190
> Project: Mahout
> Issue Type: Bug
> Reporter: Dan Filimon
>
> Currently when calling .assign() on a SASV with another vector and a custom
> function, it will iterate through it and assign every single entry while also
> referring it by index.
> This makes the process *hugely* expensive. (on a run of BallKMeans on the 20
> newsgroups data set, profiling reveals that 92% of the runtime was spent
> updating assigning the vectors).
> Here's a prototype patch:
> https://github.com/dfilimon/mahout/commit/63998d82bb750150a6ae09052dadf6c326c62d3d
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