File: randajtai.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) 2005-2009 Damien Stehle
    Copyright (C) 2007 David Cade
    Copyright (C) 2010 William Hart
   
******************************************************************************/

#include <math.h>
#include "fmpz_mat.h"

void
fmpz_mat_randajtai(fmpz_mat_t mat, flint_rand_t state, double alpha)
{
    const slong c = mat->c, r = mat->r, d = r;

    slong i, j;
    fmpz_t tmp;

    if (c != r)
    {
        flint_printf("Exception (fmpz_mat_ajtai): Non-square matrix.\n");
        abort();
    }

    fmpz_init(tmp);

    for (i = 0; i < d; i++)
    {
        mp_bitcnt_t bits = (mp_bitcnt_t) pow((double) (2 * d - i), alpha);

        fmpz_one(tmp);
        fmpz_mul_2exp(tmp, tmp, bits);
        fmpz_sub_ui(tmp, tmp, 1);
        fmpz_randm(mat->rows[i] + i, state, tmp);
        fmpz_add_ui(mat->rows[i] + i, mat->rows[i] + i, 2);
        fmpz_fdiv_q_2exp(mat->rows[i] + i, mat->rows[i] + i, 1);

        for (j = i + 1; j < d; j++)
        {
            fmpz_randm(mat->rows[j] + i, state, tmp);
            if (n_randint(state, 2))
                fmpz_neg(mat->rows[j] + i, mat->rows[j] + i);
            fmpz_zero(mat->rows[i] + j);
        }
    }

    fmpz_clear(tmp);
}