Collatz using libgmp.

collatz.c

#include <stdio.h>
#include <stdint.h>
#include <gmp.h>

int main()
{
    //const char* startValue = "45411764953495434350345765765756765750345456565445435436536546545324213324233";
    const char* startValue = "999349349859230394049534503485093452390984540385348304894503459235843908542390482950283945048902849230583496038920385934087";

    // bisection counter
    uint64_t bisections = 0;

    // multiplication counter
    uint64_t multiplications = 0;

    mpz_t x;
    mpz_init_set_str(x, startValue, 10);

    //while(x != 1)
    while(mpz_cmp_ui(x, 1) != 0)
    {
        //if(x % 2 == 0)
        if(mpz_even_p(x))
        {
            //x = x/2;
            mpz_cdiv_q_ui(x, x, 2);
            bisections++;
        }
        else
        {
            //x = x*3 + 1;
            mpz_mul_ui(x, x, 3);
            mpz_add_ui(x, x, 1);

            multiplications++;
        }
    }

    //printf("Finished. Start value was %lld, iterations: %lld, bisections: %lld, multiplications: %lld\n", y, bisections + multiplications, bisections, multiplications);

    printf("Finished. Start value was %s, iterations: %lld, bisections: %lld, multiplications: %lld\n", startValue, bisections + multiplications, bisections, multiplications);
}