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MathGroup Archive 2005

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Still bug in Random

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61742] Still bug in Random
  • From: "Pedrob P.B. de Oliveira" <pedrob at mackenzie.br>
  • Date: Fri, 28 Oct 2005 03:25:21 -0400 (EDT)
  • Reply-to: "Pedrob P.B. de Oliveira" <pedrob at mackenzie.br>
  • Sender: owner-wri-mathgroup at wolfram.com

I've just tried Mathematica 5.2 in respect to an old bug in Random[ ], as
pointed out in the Mathgroup posting

Subject: [mg61742] [mg47333] bug in Random 
From: Veit Elser <ve10 at cornell.edu> 
To: mathgroup at smc.vnet.net

and the bad news is that the bug remains...

The problem is a correlation in the random numbers generated from running
the expressions

r=Table[Random[Integer,{1,2^62}],{10^5}];
Union[Table[r[[i]]+r[[i+24]]-r[[i+20]],{i,10^5-24}]]

which, surprisingly, yields simply

{-2147483647, 1, 2147483649, 4611686016279904256,4611686018427387904, 
4611686020574871552}

By the way, last year I got in touch with WRI's support in respect to the
bug and, after about 2 months awaiting, all I could get as a reply was a
workaround that, disapointingly, had been proposed in Mathgroup in 2000...!!

This is really weird...

..Pedro

Pedro P.B. de Oliveira
Universidade Presbiteriana Mackenzie
Faculdade de Computação e Informática & Pós-Graduação em Engenharia Elétrica
Rua da Consolação 896, Consolação
01302-907 São Paulo, SP - Brazil
Email: pedrob at mackenzie.br
Web: www.mackenzie.br/pedrob
Phone: +55 (0)11 3236-8711
Fax: +55 (0)11 3236-8600




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