pqc/external/flint-2.4.3/fmpz/randtest_mod.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 <stdio.h>
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "ulong_extras.h"
void
fmpz_randtest_mod(fmpz_t f, flint_rand_t state, const fmpz_t m)
{
fmpz_t t;
fmpz_init(t);
fmpz_randtest_unsigned(t, state, fmpz_bits(m) + 2);
fmpz_mod(t, t, m);
if (n_randlimb(state) & UWORD(1))
{
fmpz_sub(t, m, t);
fmpz_sub_ui(t, t, UWORD(1));
}
fmpz_set(f, t);
fmpz_clear(t);
}
void
fmpz_randtest_mod_signed(fmpz_t f, flint_rand_t state, const fmpz_t m)
{
/* Randomly generate m/2 when included in the range */
if ((n_randlimb(state) % 32 == 1) && (fmpz_fdiv_ui(m, 2) == 0))
{
fmpz_fdiv_q_ui(f, m, UWORD(2));
}
else
{
fmpz_t t;
fmpz_init(t);
fmpz_tdiv_q_ui(t, m, UWORD(2));
fmpz_randtest_mod(t, state, t);
if (n_randlimb(state) & UWORD(1))
{
fmpz_neg(t, t);
}
fmpz_set(f, t);
fmpz_clear(t);
}
}