pqc/external/flint-2.4.3/fmpz/dlog.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 <math.h>
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "ulong_extras.h"
double
fmpz_dlog(const fmpz_t x)
{
if (!COEFF_IS_MPZ(*x))
{
return log(*x);
}
else
{
double s;
slong e;
#if defined(__MPIR_VERSION)
s = mpz_get_d_2exp(&e, COEFF_TO_PTR(*x));
#else
s = mpz_get_d_2exp((long *) &e, COEFF_TO_PTR(*x));
#endif
return log(s) + e * 0.69314718055994530942;
}
}