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72 lines
2.6 KiB
C
72 lines
2.6 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, 2011 Free Software Foundation
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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 "mpa.h"
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#include <math_private.h>
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#ifndef SECTION
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# define SECTION
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#endif
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void __mpexp(mp_no *x, mp_no *y, int p);
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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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double w,z,res,eps=3.0e-26;
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#if 0
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double y;
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#endif
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int p;
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#if 0
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int orig,i;
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#endif
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mp_no mpx, mpy, mpz,mpw,mpeps,mpcor;
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p=6;
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__dbl_mp(x,&mpx,p); /* Convert a double precision number x */
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/* into a multiple precision number mpx with prec. p. */
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__mpexp(&mpx, &mpy, p); /* Multi-Precision exponential function */
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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) return w;
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else { /* if calculating is not exactly */
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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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return res;
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}
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}
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