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Bug #6066 shuffle() implementation fails
Submitted: 2000-08-10 05:35 UTC Modified: 2002-10-01 16:22 UTC
From: mbravo at acm dot org Assigned:
Status: Not a bug Package: Misbehaving function
PHP Version: 3.0.16 OS: FreeBSD 4.1-Release
Private report: No CVE-ID: None
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From: mbravo at acm dot org
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 [2000-08-10 05:35 UTC] mbravo at acm dot org 
Detailed description -

an array of 8 elements, being shuffled repeatedly, with 
srand((double)microtime()*100000) being called each time, produces very unrandom results, namely, only 3 elements of 8 ever land in the first row (tested for 3x24hours).

Testing platform was an installation of Tobias Ratschiller phpAds (I will be submitting a patch to it which gets rid of shuffle() RSN)

While the same application (phpAds) using the same shuffle() method worked ok on Linux (2.2.x), I naively believe that actual implementation of shuffle() might be somehow improved, inctead of relying on system's random generator being nicely symmetrical (if I understood the implementation correctly). Replacing usage of system random generator with mt_rand (internally) might also be a good idea.

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AllCommentsChangesGit/SVN commitsRelated reports
 [2000-08-10 05:45 UTC] waldschrott@php.net 
There?s no information in the docs which logic shuffle() uses, should be added....
 [2002-10-01 15:36 UTC] hholzgra@php.net 
there's a more recent report ob php 4 behaviour
 [2002-10-01 16:22 UTC] sniper@php.net 
and it's better to add comments to that one than have this open..
 
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