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77 lines
1.8 KiB
77 lines
1.8 KiB
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/* @(#)e_remainder.c 1.3 95/01/18 */ |
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/* |
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* ==================================================== |
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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* |
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* Developed at SunSoft, a Sun Microsystems, Inc. business. |
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* Permission to use, copy, modify, and distribute this |
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* software is freely granted, provided that this notice |
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* is preserved. |
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* ==================================================== |
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*/ |
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/* __ieee754_remainder(x,p) |
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* Return : |
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* returns x REM p = x - [x/p]*p as if in infinite |
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* precise arithmetic, where [x/p] is the (infinite bit) |
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* integer nearest x/p (in half way case choose the even one). |
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* Method : |
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* Based on ieee_fmod() return x-[x/p]chopped*p exactlp. |
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*/ |
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#include "fdlibm.h" |
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#ifdef __STDC__ |
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static const double zero = 0.0; |
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#else |
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static double zero = 0.0; |
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#endif |
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#ifdef __STDC__ |
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double __ieee754_remainder(double x, double p) |
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#else |
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double __ieee754_remainder(x,p) |
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double x,p; |
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#endif |
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{ |
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int hx,hp; |
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unsigned sx,lx,lp; |
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double p_half; |
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hx = __HI(x); /* high word of x */ |
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lx = __LO(x); /* low word of x */ |
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hp = __HI(p); /* high word of p */ |
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lp = __LO(p); /* low word of p */ |
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sx = hx&0x80000000; |
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hp &= 0x7fffffff; |
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hx &= 0x7fffffff; |
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/* purge off exception values */ |
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if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ |
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if((hx>=0x7ff00000)|| /* x not finite */ |
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((hp>=0x7ff00000)&& /* p is NaN */ |
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(((hp-0x7ff00000)|lp)!=0))) |
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return (x*p)/(x*p); |
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if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ |
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if (((hx-hp)|(lx-lp))==0) return zero*x; |
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x = ieee_fabs(x); |
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p = ieee_fabs(p); |
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if (hp<0x00200000) { |
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if(x+x>p) { |
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x-=p; |
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if(x+x>=p) x -= p; |
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} |
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} else { |
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p_half = 0.5*p; |
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if(x>p_half) { |
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x-=p; |
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if(x>=p_half) x -= p; |
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} |
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} |
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__HI(x) ^= sx; |
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return x; |
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}
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