mpir/gmp exp(1) benchmark

gistfile1.c

#include <stdio.h>
#include <math.h>
#include "gmp.h"
#include "time.h"
#define ulong unsigned long

void
mpz_bsplit(mpz_t p, mpz_t q, ulong a, ulong b)
{
    if (b - a == 1)
    {
        mpz_set_ui(p, 1);
        mpz_set_ui(q, b);
    }
    else
    {
        ulong m;

        mpz_t p1, q2;

        mpz_init(p1);
        mpz_init(q2);

        m = a + (b - a) / 2;

        mpz_bsplit(p1, q, a, m);
        mpz_bsplit(p, q2, m, b);

        mpz_mul(p1, p1, q2);
        mpz_add(p, p, p1);
        mpz_mul(q, q, q2);

        mpz_clear(p1);
        mpz_clear(q2);
    }
}

void mpz_e(mpz_t y, ulong prec)
{
    ulong N;
    mpz_t p, q;

    N = 1.1 * prec / log(prec) + 20;

    mpz_init(p);
    mpz_init(q);

    mpz_bsplit(p, q, 0, N);

    mpz_add(p, p, q);
    mpz_mul_2exp(p, p, prec);
    mpz_tdiv_q(y, p, q);

    mpz_clear(p);
    mpz_clear(q);
}

void time_e(void)
{
    ulong digits, prec, count, iter;
    clock_t t;

    mpz_t y;
    mpz_init(y);

    printf("\n");

    for (digits = 100; digits <= 10000000; digits *= 10)
    {
        prec = digits * 3.333;

        printf("digits = %lu: ", digits);
        fflush(stdout);

        iter = 1;
        if (digits == 100) iter = 100000;
        if (digits == 1000) iter = 10000;
        if (digits == 10000) iter = 100;
        if (digits == 100000) iter = 10;
        if (digits == 1000000) iter = 1;

        t = clock();
        for (count = 0; count < iter; count++)
            mpz_e(y, prec);
        t = clock() - t;

        printf("%g s\n", ((double) t) / CLOCKS_PER_SEC / iter);

    }

    mpz_clear(y);
}

int main()
{
    time_e();
}