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131 lines
4.5 KiB
C
131 lines
4.5 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 urem.c */
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/* */
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/* FUNCTION: uremainder */
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/* */
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/* An ultimate remainder routine. Given two IEEE double machine numbers x */
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/* ,y it computes the correctly rounded (to nearest) value of remainder */
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/* of dividing x by y. */
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/* Assumption: Machine arithmetic operations are performed in */
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/* round to nearest mode of IEEE 754 standard. */
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/* */
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/* ************************************************************************/
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#include "endian.h"
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#include "mydefs.h"
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#include "urem.h"
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#include "MathLib.h"
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#include <math_private.h>
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/**************************************************************************/
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/* An ultimate remainder routine. Given two IEEE double machine numbers x */
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/* ,y it computes the correctly rounded (to nearest) value of remainder */
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/**************************************************************************/
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double __ieee754_remainder(double x, double y)
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{
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double z,d,xx;
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#if 0
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double yy;
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#endif
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int4 kx,ky,n,nn,n1,m1,l;
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#if 0
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int4 m;
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#endif
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mynumber u,t,w={{0,0}},v={{0,0}},ww={{0,0}},r;
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u.x=x;
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t.x=y;
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kx=u.i[HIGH_HALF]&0x7fffffff; /* no sign for x*/
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t.i[HIGH_HALF]&=0x7fffffff; /*no sign for y */
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ky=t.i[HIGH_HALF];
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/*------ |x| < 2^1023 and 2^-970 < |y| < 2^1024 ------------------*/
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if (kx<0x7fe00000 && ky<0x7ff00000 && ky>=0x03500000) {
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if (kx+0x00100000<ky) return x;
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if ((kx-0x01500000)<ky) {
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z=x/t.x;
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v.i[HIGH_HALF]=t.i[HIGH_HALF];
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d=(z+big.x)-big.x;
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xx=(x-d*v.x)-d*(t.x-v.x);
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if (d-z!=0.5&&d-z!=-0.5) return (xx!=0)?xx:((x>0)?ZERO.x:nZERO.x);
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else {
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if (ABS(xx)>0.5*t.x) return (z>d)?xx-t.x:xx+t.x;
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else return xx;
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}
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} /* (kx<(ky+0x01500000)) */
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else {
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r.x=1.0/t.x;
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n=t.i[HIGH_HALF];
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nn=(n&0x7ff00000)+0x01400000;
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w.i[HIGH_HALF]=n;
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ww.x=t.x-w.x;
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l=(kx-nn)&0xfff00000;
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n1=ww.i[HIGH_HALF];
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m1=r.i[HIGH_HALF];
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while (l>0) {
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r.i[HIGH_HALF]=m1-l;
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z=u.x*r.x;
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w.i[HIGH_HALF]=n+l;
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ww.i[HIGH_HALF]=(n1)?n1+l:n1;
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d=(z+big.x)-big.x;
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u.x=(u.x-d*w.x)-d*ww.x;
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l=(u.i[HIGH_HALF]&0x7ff00000)-nn;
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}
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r.i[HIGH_HALF]=m1;
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w.i[HIGH_HALF]=n;
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ww.i[HIGH_HALF]=n1;
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z=u.x*r.x;
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d=(z+big.x)-big.x;
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u.x=(u.x-d*w.x)-d*ww.x;
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if (ABS(u.x)<0.5*t.x) return (u.x!=0)?u.x:((x>0)?ZERO.x:nZERO.x);
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else
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if (ABS(u.x)>0.5*t.x) return (d>z)?u.x+t.x:u.x-t.x;
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else
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{z=u.x/t.x; d=(z+big.x)-big.x; return ((u.x-d*w.x)-d*ww.x);}
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}
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} /* (kx<0x7fe00000&&ky<0x7ff00000&&ky>=0x03500000) */
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else {
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if (kx<0x7fe00000&&ky<0x7ff00000&&(ky>0||t.i[LOW_HALF]!=0)) {
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y=ABS(y)*t128.x;
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z=__ieee754_remainder(x,y)*t128.x;
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z=__ieee754_remainder(z,y)*tm128.x;
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return z;
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}
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else {
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if ((kx&0x7ff00000)==0x7fe00000&&ky<0x7ff00000&&(ky>0||t.i[LOW_HALF]!=0)) {
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y=ABS(y);
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z=2.0*__ieee754_remainder(0.5*x,y);
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d = ABS(z);
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if (d <= ABS(d-y)) return z;
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else return (z>0)?z-y:z+y;
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}
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else { /* if x is too big */
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if (kx == 0x7ff00000 && u.i[LOW_HALF] == 0 && y == 1.0)
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return x / x;
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if (kx>=0x7ff00000||(ky==0&&t.i[LOW_HALF]==0)||ky>0x7ff00000||
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(ky==0x7ff00000&&t.i[LOW_HALF]!=0))
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return (u.i[HIGH_HALF]&0x80000000)?nNAN.x:NAN.x;
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else return x;
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}
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}
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}
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}
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strong_alias (__ieee754_remainder, __remainder_finite)
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