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87 lines
2.9 KiB
C
87 lines
2.9 KiB
C
/*
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* IBM Accurate Mathematical Library
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* written by International Business Machines Corp.
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* Copyright (C) 2001-2017 Free Software Foundation, Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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/**************************************************************************/
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/* MODULE_NAME:slowexp.c */
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/* */
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/* FUNCTION:slowexp */
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/* */
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/* FILES NEEDED:mpa.h */
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/* mpa.c mpexp.c */
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/* */
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/*Converting from double precision to Multi-precision and calculating */
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/* e^x */
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/**************************************************************************/
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#include <math_private.h>
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#include <stap-probe.h>
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#ifndef USE_LONG_DOUBLE_FOR_MP
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# include "mpa.h"
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void __mpexp (mp_no *x, mp_no *y, int p);
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#endif
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#ifndef SECTION
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# define SECTION
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#endif
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/*Converting from double precision to Multi-precision and calculating e^x */
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double
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SECTION
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__slowexp (double x)
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{
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#ifndef USE_LONG_DOUBLE_FOR_MP
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double w, z, res, eps = 3.0e-26;
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int p;
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mp_no mpx, mpy, mpz, mpw, mpeps, mpcor;
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/* Use the multiple precision __MPEXP function to compute the exponential
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First at 144 bits and if it is not accurate enough, at 768 bits. */
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p = 6;
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__dbl_mp (x, &mpx, p);
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__mpexp (&mpx, &mpy, p);
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__dbl_mp (eps, &mpeps, p);
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__mul (&mpeps, &mpy, &mpcor, p);
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__add (&mpy, &mpcor, &mpw, p);
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__sub (&mpy, &mpcor, &mpz, p);
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__mp_dbl (&mpw, &w, p);
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__mp_dbl (&mpz, &z, p);
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if (w == z)
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{
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/* Track how often we get to the slow exp code plus
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its input/output values. */
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LIBC_PROBE (slowexp_p6, 2, &x, &w);
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return w;
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}
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else
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{
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p = 32;
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__dbl_mp (x, &mpx, p);
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__mpexp (&mpx, &mpy, p);
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__mp_dbl (&mpy, &res, p);
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/* Track how often we get to the uber-slow exp code plus
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its input/output values. */
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LIBC_PROBE (slowexp_p32, 2, &x, &res);
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return res;
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}
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#else
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return (double) __ieee754_expl((long double)x);
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#endif
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}
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