Max5 API Reference

00001 /* 
00002     jit.rand.c
00003 
00004     Copyright 2001-2005 - Cycling '74
00005     Joshua Kit Clayton jkc@cycling74.com
00006         
00007 */
00008 
00009 #include "jit.common.h"
00010 
00011 long ran1(long *idum);
00012 long ran2(long *idum);
00013 
00014 /* ---- re-entrant random numbers --------- */
00015 
00016 static long seed = 1, seed2 = 1;
00017 static Boolean in=FALSE;
00018 
00019 /*
00020  *   pseudo-random number generator
00021  *
00022  */
00023  
00024 /**
00025  * Sets global random number generator seed.
00026  *
00027  * @ingroup utilitymod 
00028  *
00029  * @param   n   seed
00030  *
00031  */
00032 void jit_rand_setseed(long n)
00033 {
00034     if (!n) n = systime_ticks();
00035     if (!n) n = -777;
00036     if (n>0) n = -n;
00037     seed = seed2 = n;
00038 }
00039 
00040 /**
00041  * Generates a random value as a signed long integer.
00042  *
00043  * @ingroup utilitymod 
00044  *
00045  * @return  random value
00046  *
00047  */
00048 long jit_rand(void)
00049 {
00050     if (in) {
00051         return (ran2(&seed2));
00052     } else {
00053         in = TRUE;
00054         return (ran1(&seed));
00055         in = FALSE;
00056     }
00057 }
00058 
00059 // random number generator based on Numerical Recipes "ran1" pp. 280
00060 
00061 #define IA 16807
00062 #define IM 2147483647
00063 #define IQ 12773
00064 #define IR 2836
00065 #define NTAB 32
00066 #define NDIV (1+(IM-1)/NTAB)
00067 
00068 long ran1(long *idum)
00069 {
00070     long j,k;
00071     static long iy = 0;
00072     static long iv[NTAB];
00073     
00074     if (*idum <= 0 || !iy) {
00075         if (-(*idum) < 1)
00076             *idum = 1;
00077         else
00078             *idum = -(*idum);
00079         for (j = NTAB + 7; j >= 0; j--) {
00080             k = (*idum)/IQ;
00081             *idum = IA * (*idum - k * IQ) - IR * k;
00082             if (*idum < 0)
00083                 *idum += IM;
00084             if (j < NTAB)
00085                 iv[j] = *idum;
00086         }
00087     }
00088     iy = iv[0];
00089     k = (*idum)/IQ;
00090     *idum = IA * (*idum - k * IQ) - IR * k;
00091     if (*idum < 0)
00092         *idum += IM;
00093     j = iy/NDIV;
00094     iy = iv[j];
00095     iv[j] = *idum;
00096     return (iy);
00097 }
00098 
00099 long ran2(long *idum)
00100 {
00101     long j,k;
00102     static long iy = 0;
00103     static long iv[NTAB];
00104     
00105     if (*idum <= 0 || !iy) {
00106         if (-(*idum) < 1)
00107             *idum = 1;
00108         else
00109             *idum = -(*idum);
00110         for (j = NTAB + 7; j >= 0; j--) {
00111             k = (*idum)/IQ;
00112             *idum = IA * (*idum - k * IQ) - IR * k;
00113             if (*idum < 0)
00114                 *idum += IM;
00115             if (j < NTAB)
00116                 iv[j] = *idum;
00117         }
00118     }
00119     iy = iv[0];
00120     k = (*idum)/IQ;
00121     *idum = IA * (*idum - k * IQ) - IR * k;
00122     if (*idum < 0)
00123         *idum += IM;
00124     j = iy/NDIV;
00125     iy = iv[j];
00126     iv[j] = *idum;
00127     return (iy);
00128 }