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From: henseler@uniol.UUCP (Herwig Henseler)
Newsgroups: comp.lang.c
Subject: Re: Random long-number generator
Keywords: random maxint
Message-ID: <1540@uniol.UUCP>
Date: 22 Dec 89 12:04:12 GMT
References: <83943@linus.UUCP> <1486@skye.ed.ac.uk>
Organization: University of Oldenburg, W-Germany
Lines: 45

Hello World,

There seems to be no regular posting 'Answers to frequently asked questions'
in comp.lang.c. Here is the _best_ (!) random number generator dealing with
(long). (You can find the proof in 'Communications of ACM' 1988; I don't
know the exact number, sorry)

-------------------------------- cut here -----------------------------------
#define a_random        (long) 16807
#define m_random        (long) 2147483647
#define q_random        (long) 127773           /* m div a */
#define r_random        (long) 2836             /* m mod a */

long seed;

/* Return random value [0..1) */

double
random()
{
	seed = a_random * (seed % q_random) - r_random * (seed / q_random);
	if( seed <= 0 )
		seed += m_random;
	return( (double) seed / (double) m_random );
}

main()
{
	/* Initialize seed */
	(void) time(&seed);
	seed += getpid();
	random();

	while(1) {
		printf( "%lf\n", random() );
	}
}
-------------------------------- cut here -----------------------------------

I hope this will prevent further questions for a few months.

	bye, Herwig
--
## Herwig Henseler (CS-Student) D-2930 Varel, Tweehoernweg 69 | Brain fault- ##
## EMail: henseler@uniol.UUCP (..!uunet!unido!uniol!henseler) | core dumped  ##