GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libm/src/e_hypot.c Lines: 0 47 0.0 %
Date: 2017-11-13 Branches: 0 24 0.0 %

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/* @(#)e_hypot.c 5.1 93/09/24 */
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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 SunPro, 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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/* hypot(x,y)
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 *
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 * Method :
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 *	If (assume round-to-nearest) z=x*x+y*y
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 *	has error less than sqrt(2)/2 ulp, than
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 *	sqrt(z) has error less than 1 ulp (exercise).
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 *
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 *	So, compute sqrt(x*x+y*y) with some care as
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 *	follows to get the error below 1 ulp:
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 *
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 *	Assume x>y>0;
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 *	(if possible, set rounding to round-to-nearest)
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 *	1. if x > 2y  use
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 *		x1*x1+(y*y+(x2*(x+x1))) for x*x+y*y
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 *	where x1 = x with lower 32 bits cleared, x2 = x-x1; else
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 *	2. if x <= 2y use
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 *		t1*yy1+((x-y)*(x-y)+(t1*y2+t2*y))
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 *	where t1 = 2x with lower 32 bits cleared, t2 = 2x-t1,
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 *	yy1= y with lower 32 bits chopped, y2 = y-yy1.
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 *
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 *	NOTE: scaling may be necessary if some argument is too
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 *	      large or too tiny
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 *
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 * Special cases:
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 *	hypot(x,y) is INF if x or y is +INF or -INF; else
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 *	hypot(x,y) is NAN if x or y is NAN.
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 *
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 * Accuracy:
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 * 	hypot(x,y) returns sqrt(x^2+y^2) with error less
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 * 	than 1 ulps (units in the last place)
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 */
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#include <float.h>
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#include <math.h>
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#include "math_private.h"
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double
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hypot(double x, double y)
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{
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	double a=x,b=y,t1,t2,yy1,y2,w;
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	int32_t j,k,ha,hb;
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	GET_HIGH_WORD(ha,x);
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	ha &= 0x7fffffff;
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	GET_HIGH_WORD(hb,y);
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	hb &= 0x7fffffff;
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	if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
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	SET_HIGH_WORD(a,ha);	/* a <- |a| */
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	SET_HIGH_WORD(b,hb);	/* b <- |b| */
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	if((ha-hb)>0x3c00000) {return a+b;} /* x/y > 2**60 */
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	k=0;
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	if(ha > 0x5f300000) {	/* a>2**500 */
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	   if(ha >= 0x7ff00000) {	/* Inf or NaN */
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	       u_int32_t low;
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	       w = a+b;			/* for sNaN */
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	       GET_LOW_WORD(low,a);
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	       if(((ha&0xfffff)|low)==0) w = a;
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	       GET_LOW_WORD(low,b);
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	       if(((hb^0x7ff00000)|low)==0) w = b;
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	       return w;
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	   }
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	   /* scale a and b by 2**-600 */
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	   ha -= 0x25800000; hb -= 0x25800000;	k += 600;
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	   SET_HIGH_WORD(a,ha);
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	   SET_HIGH_WORD(b,hb);
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	}
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	if(hb < 0x20b00000) {	/* b < 2**-500 */
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	    if(hb <= 0x000fffff) {	/* subnormal b or 0 */
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	        u_int32_t low;
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		GET_LOW_WORD(low,b);
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		if((hb|low)==0) return a;
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		t1=0;
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		SET_HIGH_WORD(t1,0x7fd00000);	/* t1=2^1022 */
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		b *= t1;
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		a *= t1;
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		k -= 1022;
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	    } else {		/* scale a and b by 2^600 */
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	        ha += 0x25800000; 	/* a *= 2^600 */
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		hb += 0x25800000;	/* b *= 2^600 */
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		k -= 600;
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		SET_HIGH_WORD(a,ha);
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		SET_HIGH_WORD(b,hb);
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	    }
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	}
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    /* medium size a and b */
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	w = a-b;
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	if (w>b) {
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	    t1 = 0;
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	    SET_HIGH_WORD(t1,ha);
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	    t2 = a-t1;
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	    w  = sqrt(t1*t1-(b*(-b)-t2*(a+t1)));
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	} else {
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	    a  = a+a;
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	    yy1 = 0;
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	    SET_HIGH_WORD(yy1,hb);
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	    y2 = b - yy1;
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	    t1 = 0;
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	    SET_HIGH_WORD(t1,ha+0x00100000);
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	    t2 = a - t1;
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	    w  = sqrt(t1*yy1-(w*(-w)-(t1*y2+t2*b)));
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	}
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	if(k!=0) {
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	    u_int32_t high;
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	    t1 = 1.0;
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	    GET_HIGH_WORD(high,t1);
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	    SET_HIGH_WORD(t1,high+(k<<20));
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	    return t1*w;
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	} else return w;
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}
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DEF_STD(hypot);
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LDBL_MAYBE_CLONE(hypot);