/*
    Copyright (C) 2009, 2016 William Hart

    This file is part of FLINT.

    FLINT is free software: you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 2.1 of the License, or
    (at your option) any later version.  See <https://www.gnu.org/licenses/>.
*/

#include <stdio.h>
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"

int
main(void)
{
    int i, result;
    FLINT_TEST_INIT(state);

    flint_printf("mulmod_preinv....");
    fflush(stdout);

    for (i = 0; i < 100000 * flint_test_multiplier(); i++)
    {
        ulong a, b, d, r1, r2, q, p1, p2, dinv, norm;

        d = n_randtest_not_zero(state);
        a = n_randtest(state) % d;
        b = n_randtest(state) % d;

        count_leading_zeros(norm, d);

        dinv = n_preinvert_limb(d << norm);

        r1 = n_mulmod_preinv(a << norm, b << norm, d << norm, dinv,
                             norm) >> norm;

        umul_ppmm(p1, p2, a, b);
        p1 %= d;
        udiv_qrnnd(q, r2, p1, p2, d);

        result = (r1 == r2);
        if (!result)
        {
            flint_printf("FAIL:\n");
            flint_printf("a = %wu, b = %wu, d = %wu, dinv = %wu\n", a, b, d,
                         dinv);
            flint_printf("q = %wu, r1 = %wu, r2 = %wu\n", q, r1, r2);
            abort();
        }
    }

    FLINT_TEST_CLEANUP(state);

    flint_printf("PASS\n");
    return 0;
}