Computer Chess Club Archives




Subject: Re: random book moves/ random generator

Author: Thorsten Greiner

Date: 08:29:25 01/13/00

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On January 13, 2000 at 11:22:20, Vincent Diepeveen wrote:

>number = rand()%total;

rand() is evil. It uses a linear congruency method like

	new random number = (old random number * constant + constant) % constant

Information in low bits of 'old random number' is lost in this formula. Since
the number of seconds since 1970 is pretty much constant in lets say January
2000, the random numbers produced will be quite similar...

Also, never use modulo on the results of rand() - use something like

	rand() / (RAND_MAX / total)

since the low bits of rand() are not as random as the high bits. Or use a real
random generator - here is a good one:


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