is_prime_divisors_in_residue.c

/*=============================================================================

    This file is part of FLINT.

    FLINT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    FLINT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with FLINT; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

=============================================================================*/
/******************************************************************************

    Copyright (C) 2015 Vladimir Glazachev
   
******************************************************************************/

#include "aprcl.h"

int
is_prime_divisors_in_residue(const fmpz_t n, const fmpz_t s, ulong r)
{
    int result;
    ulong i;
    fmpz_t npow, nmul, fac;

    fmpz_init(fac);
    fmpz_init_set(npow, n);
    fmpz_mod(npow, npow, s); /* npow = n mod s */
    fmpz_init_set(nmul, npow);

    result = 1;
    for (i = 1; i < r; i++)
    {
        /* if find divisor then n is composite */
        if (fmpz_divisor_in_residue_class_lenstra(fac, n, npow, s) == 1)
        {
            result = 0;
            break;
        }
        /* npow = n^i mod s */
        fmpz_mul(npow, npow, nmul);
        fmpz_mod(npow, npow, s);
    }

    fmpz_clear(fac);
    fmpz_clear(npow);
    fmpz_clear(nmul);

    return result;
}