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/*
* C version of Marsaglia's UNI random number generator
* More or less transliterated from the Fortran -- with 1 bug fix
* Hence horrible style
*
* Features:
* ANSI C
* not callable from Fortran (yet)
*/
char uni_id[] = "$Id: random.c,v 1.7 2009/08/28 09:09:17 spb Exp spb $" ;
/*
* Global variables for rstart & uni
*/
#define PARANOID
/* need types and time */
#include <X11/Xos.h>
/* #include <sys/types.h>
* #include <sys/time.h>
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
typedef struct
{
float u[98];
float c;
float cd;
float cm;
int ui;
int uj;
}
Uni_save;
Uni_save uni_data;
float uni()
{
float luni; /* local variable for uni */
luni = uni_data.u[uni_data.ui] - uni_data.u[uni_data.uj];
if (luni < 0.0)
luni += 1.0;
uni_data.u[uni_data.ui] = luni;
if (--uni_data.ui == 0)
uni_data.ui = 97;
if (--uni_data.uj == 0)
uni_data.uj = 97;
if ((uni_data.c -= uni_data.cd) < 0.0)
uni_data.c += uni_data.cm;
if ((luni -= uni_data.c) < 0.0)
luni += 1.0;
return ((float) luni);
}
void rstart(i,j,k,l)
int i;
int j;
int k;
int l;
{
int ii, jj, m;
float s, t;
for (ii = 1; ii <= 97; ii++) {
s = 0.0;
t = 0.5;
for (jj = 1; jj <= 24; jj++) {
m = ((i*j % 179) * k) % 179;
i = j;
j = k;
k = m;
l = (53*l+1) % 169;
if (l*m % 64 >= 32)
s += t;
t *= 0.5;
}
uni_data.u[ii] = s;
}
uni_data.c = 362436.0 / 16777216.0;
uni_data.cd = 7654321.0 / 16777216.0;
uni_data.cm = 16777213.0 / 16777216.0;
uni_data.ui = 97; /* There is a bug in the original Fortran version */
uni_data.uj = 33; /* of UNI -- i and j should be SAVEd in UNI() */
}
/* ~seed_uni: this takes a single integer in the range
* 0 <= ijkl <= 900 000 000
* and produces the four smaller integers needed for rstart. It is
* based on the ideas contained in the RMARIN subroutine in
* F. James, "A Review of Pseudorandom Number Generators",
* Comp. Phys. Commun. Oct 1990, p.340
* To reduce the modifications to the existing code, seed_uni now
* takes the role of a preprocessor for rstart.
*
*/
void seed_uni(ijkl)
int ijkl;
{
int i, j, k, l, ij, kl;
if( ijkl == 0 )
{
ijkl = time((time_t *) 0);
ijkl %= 900000000;
}
/* check ijkl is within range */
if( (ijkl < 0) || (ijkl > 900000000) )
{
fprintf(stderr,"seed_uni: ijkl = %d -- out of range\n\n", ijkl);
exit(3);
}
/* decompose the long integer into the the equivalent four
* integers for rstart. This should be a 1-1 mapping
* ijkl <--> (i, j, k, l)
* though not quite all of the possible sets of (i, j, k, l)
* can be produced.
*/
ij = ijkl/30082;
kl = ijkl - (30082 * ij);
i = ((ij/177) % 177) + 2;
j = (ij % 177) + 2;
k = ((kl/169) % 178) + 1;
l = kl % 169;
#ifdef PARANOID
if( (i <= 0) || (i > 178) )
{
fprintf(stderr,"seed_uni: i = %d -- out of range\n\n", i);
exit(3);
}
if( (j <= 0) || (j > 178) )
{
fprintf(stderr,"seed_uni: j = %d -- out of range\n\n", j);
exit(3);
}
if( (k <= 0) || (k > 178) )
{
fprintf(stderr,"seed_uni: k = %d -- out of range\n\n", k);
exit(3);
}
if( (l < 0) || (l > 168) )
{
fprintf(stderr,"seed_uni: l = %d -- out of range\n\n", l);
exit(3);
}
if (i == 1 && j == 1 && k == 1)
{
fprintf(stderr,"seed_uni: 1 1 1 not allowed for 1st 3 seeds\n\n");
exit(4);
}
#endif
rstart(i, j, k, l);
}
float gaussian()
{
double pi = 3.1415926536, two = 2.0, zero = 0.0;
double ran1, ran2;
do {
ran1 = (double) uni();
} while (ran1 == zero);
ran2 = (double) uni();
return (float) ( sqrt(-two * log(ran1)) * cos(two * pi * ran2) );
}
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