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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAHOUT-1573) More explicit parallelism adjustments in math-scala DRM apis; elements of automatic re-adjustments
Date Wed, 18 Jun 2014 00:59:02 GMT

    [ https://issues.apache.org/jira/browse/MAHOUT-1573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14034677#comment-14034677
] 

ASF GitHub Bot commented on MAHOUT-1573:
----------------------------------------

Github user dlyubimov commented on the pull request:

    https://github.com/apache/mahout/pull/13#issuecomment-46384722
  
    e.g. one can write things like `A.t.%*%(A).exact_||(100)`


> More explicit parallelism adjustments in math-scala DRM apis; elements of automatic re-adjustments
> --------------------------------------------------------------------------------------------------
>
>                 Key: MAHOUT-1573
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1573
>             Project: Mahout
>          Issue Type: Task
>    Affects Versions: 0.9
>            Reporter: Dmitriy Lyubimov
>            Assignee: Dmitriy Lyubimov
>             Fix For: 1.0
>
>
> (1) add minSplit parameter pass-thru to drmFromHDFS to be able to explicitly increase
parallelism. 
> (2) add parrallelism readjustment parameter to a checkpoint() call. This implies shuffle-less
coalesce() translation to the data set before it is requested to be cached (if specified).
> Going forward, we probably should try and figure how we can automate it,  at least a
little bit. For example, the simplest automatic adjustment might include re-adjust parallelims
on load to simply fit cluster size (95% or 180% of cluster size, for example), with some rule-of-thumb
safeguards here, e.g. we cannot exceed a factor of say 8 (or whatever we configure) in splitting
each original hdfs split. We should be able to get a reasonable parallelism performance out
of the box on simple heuristics like that.



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