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110 lines
4.3 KiB
C
110 lines
4.3 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:mpexp.c */
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/* */
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/* FUNCTIONS: mpexp */
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/* */
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/* FILES NEEDED: mpa.h endian.h mpexp.h */
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/* mpa.c */
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/* */
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/* Multi-Precision exponential function subroutine */
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/* ( for p >= 4, 2**(-55) <= abs(x) <= 1024 ). */
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/*************************************************************************/
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#include "endian.h"
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#include "mpa.h"
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#include "mpexp.h"
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#ifndef SECTION
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# define SECTION
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#endif
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/* Multi-Precision exponential function subroutine (for p >= 4, */
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/* 2**(-55) <= abs(x) <= 1024). */
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void
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SECTION
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__mpexp(mp_no *x, mp_no *y, int p) {
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int i,j,k,m,m1,m2,n;
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double a,b;
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static const int np[33] = {0,0,0,0,3,3,4,4,5,4,4,5,5,5,6,6,6,6,6,6,
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6,6,6,6,7,7,7,7,8,8,8,8,8};
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static const int m1p[33]= {0,0,0,0,17,23,23,28,27,38,42,39,43,47,43,47,50,54,
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57,60,64,67,71,74,68,71,74,77,70,73,76,78,81};
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static const int m1np[7][18] = {
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
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{ 0, 0, 0, 0,36,48,60,72, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
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{ 0, 0, 0, 0,24,32,40,48,56,64,72, 0, 0, 0, 0, 0, 0, 0},
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{ 0, 0, 0, 0,17,23,29,35,41,47,53,59,65, 0, 0, 0, 0, 0},
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{ 0, 0, 0, 0, 0, 0,23,28,33,38,42,47,52,57,62,66, 0, 0},
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{ 0, 0, 0, 0, 0, 0, 0, 0,27, 0, 0,39,43,47,51,55,59,63},
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,43,47,50,54}};
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mp_no mpone = {0,{0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
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0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
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0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0}};
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mp_no mpk = {0,{0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
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0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
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0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0}};
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mp_no mps,mpak,mpt1,mpt2;
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/* Choose m,n and compute a=2**(-m) */
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n = np[p]; m1 = m1p[p]; a = __mpexp_twomm1[p].d;
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for (i=0; i<EX; i++) a *= RADIXI;
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for ( ; i>EX; i--) a *= RADIX;
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b = X[1]*RADIXI; m2 = 24*EX;
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for (; b<HALF; m2--) { a *= TWO; b *= TWO; }
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if (b == HALF) {
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for (i=2; i<=p; i++) { if (X[i]!=ZERO) break; }
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if (i==p+1) { m2--; a *= TWO; }
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}
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if ((m=m1+m2) <= 0) {
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m=0; a=ONE;
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for (i=n-1; i>0; i--,n--) { if (m1np[i][p]+m2>0) break; }
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}
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/* Compute s=x*2**(-m). Put result in mps */
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__dbl_mp(a,&mpt1,p);
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__mul(x,&mpt1,&mps,p);
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/* Evaluate the polynomial. Put result in mpt2 */
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mpone.e=1; mpone.d[0]=ONE; mpone.d[1]=ONE;
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mpk.e = 1; mpk.d[0] = ONE; mpk.d[1]=__mpexp_nn[n].d;
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__dvd(&mps,&mpk,&mpt1,p);
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__add(&mpone,&mpt1,&mpak,p);
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for (k=n-1; k>1; k--) {
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__mul(&mps,&mpak,&mpt1,p);
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mpk.d[1]=__mpexp_nn[k].d;
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__dvd(&mpt1,&mpk,&mpt2,p);
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__add(&mpone,&mpt2,&mpak,p);
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}
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__mul(&mps,&mpak,&mpt1,p);
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__add(&mpone,&mpt1,&mpt2,p);
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/* Raise polynomial value to the power of 2**m. Put result in y */
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for (k=0,j=0; k<m; ) {
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__mul(&mpt2,&mpt2,&mpt1,p); k++;
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if (k==m) { j=1; break; }
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__mul(&mpt1,&mpt1,&mpt2,p); k++;
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}
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if (j) __cpy(&mpt1,y,p);
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else __cpy(&mpt2,y,p);
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return;
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}
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