[jira] [Commented] (MAHOUT-673) Stochastic projection (SSVD) to use 64bit murmur hash to produce uniform distribution matrix elements

["Dmitriy Lyubimov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAHOUT-673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13020880#comment-13020880 ] 

Dmitriy Lyubimov commented on MAHOUT-673:
-----------------------------------------

Oh. This of course is not right.

> Stochastic projection (SSVD) to use 64bit murmur hash to produce uniform distribution matrix elements
> -----------------------------------------------------------------------------------------------------
>
>                 Key: MAHOUT-673
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-673
>             Project: Mahout
>          Issue Type: Improvement
>    Affects Versions: 0.4
>            Reporter: Dmitriy Lyubimov
>            Assignee: Dmitriy Lyubimov
>            Priority: Minor
>             Fix For: 0.6
>
>         Attachments: MAHOUT-673-1.patch
>
>
> So, per earlier discussion on the list: for random matrix Omega in stochastic projection, let's use murmur hash to generate uniformly distributed elements in a closed interval (-1,+1] instead of using Random.nextGaussian(). 
> I am not sure if there's really compelling mathematical reason to do this but maybe it's just faster and more inline with practice accepted in Mahout for all this. 
> The murmur 64bit value is already in the code. I just need to figure the optimal way to convert it into a uniform distribution.
> Github url for this issue tree: https://github.com/dlyubimov/mahout-commits/branches/MAHOUT-673, pull requests are welcome.

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