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Posted to dev@mahout.apache.org by "Robin Anil (JIRA)" <ji...@apache.org> on 2013/04/10 23:43:16 UTC
[jira] [Commented] (MAHOUT-1190) SequentialAccessSparseVector
function assignment is very slow
[ https://issues.apache.org/jira/browse/MAHOUT-1190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13628298#comment-13628298 ]
Robin Anil commented on MAHOUT-1190:
------------------------------------
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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