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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1322) Negative integer seed for MersenneTwister is not working.
Date Tue, 09 Feb 2016 13:46:18 GMT

    [ https://issues.apache.org/jira/browse/MATH-1322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15138953#comment-15138953
] 

Gilles commented on MATH-1322:
------------------------------

bq. If seed is negative, longMT also becomes negative.

I'd rather expect that both types result in the same value.
Why is it a problem?

The documentation does not seem to imply any constraint on the argument.

Do I understand correctly that if your patch were applied, each of the following calls would
result in the generator being in a different state:
{code}
rng.setSeed(-1);
rng.setSeed((long) -1);
{code}
?

> Negative integer seed for MersenneTwister is not working.
> ---------------------------------------------------------
>
>                 Key: MATH-1322
>                 URL: https://issues.apache.org/jira/browse/MATH-1322
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.6
>            Reporter: Morikawa Joe
>              Labels: patch
>         Attachments: MersenneTwister.patch
>
>
> MersenneTwister.setSeed(int seed) has a bug.
> If seed is negative, longMT also becomes negative.
> First 32 bits are filled by 0xFFFFFFFF.
> But it should be positive. First 32 bits should be filled by 0x00000000.
> Ex) Integer -1 is 0xffffffff. 
> Long -1 is 0xffffffffffffffff.
> Long 0xffffffff is 4294967295.
> I created simple patch. 



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