simulacion-permeabilidad/fftma_module/gen/lib_src/maxfactor.c

#include "genlib.h"
#include "log.h"

/*determines the greatest prime factor of an integer*/
int maxfactor(int n) {
    clock_t t = clock();

    log_info("RESULT = in progress, n = %d", n);

    int test_fact(int* pnum, int fact, int* pmaxfac);
    int lnum, fact;
    int maxfac;

    maxfac = 1;
    lnum = n;

    if (lnum != 0 && lnum != 1) {
        fact = 2;
        if (test_fact(&lnum, fact, &maxfac)) {
            fact = 3;
            if (test_fact(&lnum, fact, &maxfac)) {
                fact = 5;
                for (;;) {
                    if (!test_fact(&lnum, fact, &maxfac))
                        break;
                    fact += 2;
                    if (!test_fact(&lnum, fact, &maxfac))
                        break;
                    fact += 4;
                }
            }
        }
        if (lnum != 1) {
            if (lnum > maxfac)
                maxfac = lnum;
        }
    }

    t = clock() - t;
    double time_taken = ((double)t)/CLOCKS_PER_SEC; // calculate the elapsed time

    log_info("RESULT = success, maxfac = %d, ELAPSED = %f seconds", maxfac, time_taken);
    return maxfac;
}