Re: Generating 2 independent random numbers

From:
"Thomas J. Gritzan" <phygon_antispam@gmx.de>
Newsgroups:
comp.lang.c++
Date:
Thu, 29 May 2008 12:22:54 +0200
Message-ID:
<g1m06o$dvr$1@newsreader2.netcologne.de>
James Kanze schrieb:

For example, consider the
following code:

#include <stdlib.h>
#include <iostream>

int main() {
        srand(1);

        int i;

        for (i=0; i<9; i++)
                std::cout << rand() << "\t";
        std::cout << "\n";

        for (; i<RAND_MAX; i++)
                rand();

        for (i=0; i<9; i++)
                std::cout << rand() << "\t";
        std::cout << "\n";
        return 0;
}

According to your statements, the two lines should be
identical (with a possible offset).


If the period of the generator is RAND_MAX, the middle loop
should execute RAND_MAX-9, not RAND_MAX, for the two lines to
be the same.


It will. The middle loop doesn't reset i to 0.

Not that that actually changes the concrete results. As you
say, the period is almost always longer than RAND_MAX. (On a
lot of systems, RAND_MAX is only 32767, presumably for some
obscure historical reason.)


--
Thomas

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