File: snf.c

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flint 2.5.2-19
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/*=============================================================================

    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) 2014 Alex J. Best

******************************************************************************/

#include "fmpz_mat.h"

void
fmpz_mat_snf(fmpz_mat_t S, const fmpz_mat_t A)
{
    fmpz_t det;
    slong m = A->r, n = A->c, b = fmpz_mat_max_bits(A), cutoff = 9;

    if (b <= 2)
        cutoff = 15;
    else if (b <= 4)
        cutoff = 13;
    else if (b <= 8)
        cutoff = 13;
    else if (b <= 16)
        cutoff = 11;
    else if (b <= 32)
        cutoff = 11;
    else if (b <= 64)
        cutoff = 10;

    if (FLINT_MAX(m, n) < cutoff || m != n)
        fmpz_mat_snf_kannan_bachem(S, A);
    else
    {
        fmpz_init(det);
        fmpz_mat_det(det, A);
        if (!fmpz_is_zero(det))
        {
            fmpz_abs(det, det);
            fmpz_mat_snf_iliopoulos(S, A, det);
        }
        else
        {
            fmpz_mat_snf_kannan_bachem(S, A);
        }
        fmpz_clear(det);
    }
}