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/*
* IBM Accurate Mathematical Library
* written by International Business Machines Corp.
* Copyright (C) 2001-2013 Free Software Foundation, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
/**************************************************************************/
/* MODULE_NAME:slowexp.c */
/* */
/* FUNCTION:slowexp */
/* */
/* FILES NEEDED:mpa.h */
/* mpa.c mpexp.c */
/* */
/*Converting from double precision to Multi-precision and calculating */
/* e^x */
/**************************************************************************/
#include <math_private.h>
#ifndef USE_LONG_DOUBLE_FOR_MP
# include "mpa.h"
void __mpexp (mp_no *x, mp_no *y, int p);
#endif
#ifndef SECTION
# define SECTION
#endif
/*Converting from double precision to Multi-precision and calculating e^x */
double
SECTION
__slowexp (double x)
{
#ifndef USE_LONG_DOUBLE_FOR_MP
double w, z, res, eps = 3.0e-26;
int p;
mp_no mpx, mpy, mpz, mpw, mpeps, mpcor;
/* Use the multiple precision __MPEXP function to compute the exponential
First at 144 bits and if it is not accurate enough, at 768 bits. */
p = 6;
__dbl_mp (x, &mpx, p);
__mpexp (&mpx, &mpy, p);
__dbl_mp (eps, &mpeps, p);
__mul (&mpeps, &mpy, &mpcor, p);
__add (&mpy, &mpcor, &mpw, p);
__sub (&mpy, &mpcor, &mpz, p);
__mp_dbl (&mpw, &w, p);
__mp_dbl (&mpz, &z, p);
if (w == z)
return w;
else
{
p = 32;
__dbl_mp (x, &mpx, p);
__mpexp (&mpx, &mpy, p);
__mp_dbl (&mpy, &res, p);
return res;
}
#else
return (double) __ieee754_expl((long double)x);
#endif
}
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