#include <math.h>
#include <time.h>

/* compute the length for one dimension*/
int length(int N, int i, double* scf, double* ap, double D, int Nvari, int cores) {
    int maxfactor(int n, int cores);
    double temp1, temp2;
    int n, j, k, nmax;
    int nlimit = 13;

    if (N == 1) {
        n = 1;
    } else {

        for (k = 0; k < Nvari; k++) {
            temp1 = fabs(ap[9 * k + i]) * scf[3 * k] * scf[3 * k];
            for (j = 1; j < 3; j++) {
                temp2 = fabs(ap[9 * k + 3 * j + i]) * scf[3 * k + j] * scf[3 * k + j];
                if (temp2 > temp1)
                    temp1 = temp2;
            }
        }
        temp1 = sqrt(temp1);
        temp1 /= (double)D;
        if ((double)N / temp1 < 2.) {
            n = N + (int)(2 * temp1);
        } else {
            n = N + (int)temp1;
        }
        if ((n % 2) != 0)
            n = n + 1;
        nmax = maxfactor(n, cores);
        while (nmax > nlimit) {
            n += 2;
            nmax = maxfactor(n, cores);
        }
    }

    return n;
}