source: tags/arb_5.5/ARBDB/admath.c

#include <stdlib.h>
#include <stdio.h>
/* #include <malloc.h> */
#include <string.h>
#include <math.h>
#include <time.h>

/*#include <arbdb.h>*/
#include "adlocal.h"

double GB_log_fak(int n){
    /* returns log(n!) */
    static int     max_n = 0;
    static double *res   = 0;
    
    if (n<=1) return 0.0;       /* log 1 = 0 */

    if (n >= max_n){
        double sum = 0;
        int i;
        freeset(res, NULL);
        max_n = n + 100;
        res = (double *)GB_calloc(sizeof(double),max_n);
        for (i=1;i<max_n;i++){
            sum += log((double)i);
            res[i] = sum;
        }
    }
    return res[n];
}

/* ---------------------------------- */
/*      random number generation      */
/* ---------------------------------- */

static int randomSeeded = 0;

double GB_frandom() {
    /* produces a random number in range [0.0 .. 1.0] */
    if (!randomSeeded) {
        srand(time(0));
        randomSeeded = 1;;
    }
    return ((double)rand())/RAND_MAX;
}

int GB_random(int range) {
    /* produces a random number in range [0 .. range-1] */
    if (!randomSeeded) {
        srand(time(0));
        randomSeeded = 1;
    }

#if defined(DEBUG)
    if (range>RAND_MAX) {
        printf("Warning: range to big for random granularity (%i > %i)\n", range, RAND_MAX);
    }
#endif /* DEBUG */

    return (int)(rand()*((double)range) / (RAND_MAX+1.0));
}