pqc/external/flint-2.4.3/fmpz_mat/solve_bound.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
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) 2011 Fredrik Johansson
******************************************************************************/
#include "fmpz_mat.h"
void
fmpz_mat_solve_bound(fmpz_t N, fmpz_t D,
const fmpz_mat_t A, const fmpz_mat_t B)
{
slong i, j, m, n;
fmpz_t t, u;
m = B->r;
n = B->c;
fmpz_mat_det_bound(D, A);
fmpz_init(t);
fmpz_init(u);
fmpz_zero(t);
/* Largest column norm of B */
for (j = 0; j < n; j++)
{
fmpz_zero(u);
for (i = 0; i < m; i++)
fmpz_addmul(u, fmpz_mat_entry(B, i, j), fmpz_mat_entry(B, i, j));
if (fmpz_cmp(t, u) < 0)
fmpz_set(t, u);
}
fmpz_sqrtrem(t, u, t);
if (!fmpz_is_zero(u))
fmpz_add_ui(t, t, UWORD(1));
fmpz_mul(N, D, t);
fmpz_clear(t);
fmpz_clear(u);
}