source: tags/initial/ARBDB/admath.c

#include <stdlib.h>
#include <stdio.h>
#include <malloc.h>
#include <string.h>
#include <math.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;
        GB_DELETE(res);
        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];
}