pqc/external/flint-2.4.3/arith/dedekind_sum_coprime.c
2014-05-24 23:16:06 +02:00

55 lines
1.7 KiB
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) 2011 Fredrik Johansson
******************************************************************************/
#include "arith.h"
/* Small enough that a numerical computation is safe */
#define DOUBLE_CUTOFF (UWORD(1) << 21)
void
arith_dedekind_sum_coprime(fmpq_t s, const fmpz_t h, const fmpz_t k)
{
if (fmpz_cmp_ui(k, DOUBLE_CUTOFF) < 0)
{
double t;
t = arith_dedekind_sum_coprime_d(*h, *k) * (6 * (*k));
/* Round to nearest after truncation */
if (t > 0)
t += 0.5;
else
t -= 0.5;
fmpz_set_d(fmpq_numref(s), t);
fmpz_set_ui(fmpq_denref(s), UWORD(6) * (*k));
fmpq_canonicalise(s);
}
else
{
arith_dedekind_sum_coprime_large(s, h, k);
}
}