1 /* lran2.h

     2  * by Wolfram Gloger 1996.

     3  *

     4  * A small, portable pseudo-random number generator.

     5  */

     6 

     7 #ifndef _LRAN2_H

     8 #define _LRAN2_H

     9 

    10 #define LRAN2_MAX 714025l /* constants for portable */

    11 #define IA	  1366l	  /* random number generator */

    12 #define IC	  150889l /* (see e.g. `Numerical Recipes') */

    13 

    14 struct lran2_st {

    15     long x, y, v[97];

    16 };

    17 

    18 static void

    19 lran2_init(struct lran2_st* d, long seed)

    20 {

    21     long x;

    22     int j;

    23 

    24     x = (IC - seed) % LRAN2_MAX;

    25     if(x < 0) x = -x;

    26     for(j=0; j<97; j++) {

    27 	x = (IA*x + IC) % LRAN2_MAX;

    28 	d->v[j] = x;

    29     }

    30     d->x = (IA*x + IC) % LRAN2_MAX;

    31     d->y = d->x;

    32 }

    33 

    34 #ifdef __GNUC__

    35 __inline__

    36 #endif

    37 static long

    38 lran2(struct lran2_st* d)

    39 {

    40     int j = (d->y % 97);

    41 

    42     d->y = d->v[j];

    43     d->x = (IA*d->x + IC) % LRAN2_MAX;

    44     d->v[j] = d->x;

    45     return d->y;

    46 }

    47 

    48 #undef IA

    49 #undef IC

    50 

    51 #endif