Jump to content
  • Advertisement
Sign in to follow this  
Ronin28

Random Values

This topic is 4635 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Advertisement
Guest Anonymous Poster
I don't think there are any other "standard" functions... If you need anything better, you need to code your own.

Share this post


Link to post
Share on other sites
Taken from Glenn Rhoads' page:

/* linear congruential generator. Generator x[n+1] = a * x[n] mod m */

#define RAND_INT(l,h) (((int)(random() * ((double)(h)-(l)+1))) + (l))
double random (void); /* return the next random number x: 0 <= x < 1*/
void rand_seed (unsigned int); /* seed the generator */

static unsigned int SEED = 93186752;

double random ()
{
/* The following parameters are recommended settings based on research
uncomment the one you want. */


static unsigned int a = 1588635695, m = 4294967291U, q = 2, r = 1117695901;
/* static unsigned int a = 1223106847, m = 4294967291U, q = 3, r = 625646750;*/
/* static unsigned int a = 279470273, m = 4294967291U, q = 15, r = 102913196;*/
/* static unsigned int a = 1583458089, m = 2147483647, q = 1, r = 564025558; */
/* static unsigned int a = 784588716, m = 2147483647, q = 2, r = 578306215; */
/* static unsigned int a = 16807, m = 2147483647, q = 127773, r = 2836; */
/* static unsigned int a = 950706376, m = 2147483647, q = 2, r = 246070895; */

SEED = a*(SEED % q) - r*(SEED / q);
return ((double)SEED / (double)m);
}

void rand_seed (unsigned int init) {if (init != 0) SEED = init;}





This is the simplest version he offers. There are many more implementations on his page. Interesting stuff.

EDIT: If you wish to learn more about linear congruential generators and how they relate to PRNGs, the Wikipedia article is very helpful.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

Participate in the game development conversation and more when you create an account on GameDev.net!

Sign me up!