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authorRoland McGrath <roland@gnu.org>1996-03-05 21:41:30 +0000
committerRoland McGrath <roland@gnu.org>1996-03-05 21:41:30 +0000
commitf7eac6eb504f4baf13dbb4d26717942df050ebe6 (patch)
tree95ff129c06c7f6f246a5e2bfa489ba6382659d19 /sysdeps/libm-ieee754/e_hypot.c
parent1521668f2afae1dc2ef5d7ffaeb84353b36874dd (diff)
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Mon Mar 4 20:54:40 1996 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>
	* Makeconfig ($(common-objpfx)config.make): Depend on config.h.in.


Mon Mar  4 17:35:09 1996  Roland McGrath  <roland@charlie-brown.gnu.ai.mit.edu>

	* hurd/catch-signal.c (hurd_safe_memmove): New function.
	(hurd_safe_copyin, hurd_safe_copyout): New functions.
	* hurd/hurd/sigpreempt.h: Declare them.

Sun Mar  3 08:43:44 1996  Roland McGrath  <roland@charlie-brown.gnu.ai.mit.edu>

	Replace math code with fdlibm from Sun as modified for netbsd by
	JT Conklin and Ian Taylor, including x86 FPU support.
	* sysdeps/libm-ieee754, sysdeps/libm-i387: New directories.
	* math/math_private.h: New file.
	* sysdeps/i386/fpu/Implies: New file.
	* sysdeps/ieee754/Implies: New file.
	* math/machine/asm.h, math/machine/endian.h: New files.
	* math/Makefile, math/math.h: Rewritten.
	* mathcalls.h, math/mathcalls.h: New file, broken out of math.h.
	* math/finite.c: File removed.
	* sysdeps/generic/Makefile [$(subdir)=math]: Frobnication removed.

	* math/test-math.c: Include errno.h and string.h.

	* sysdeps/unix/bsd/dirstream.h: File removed.
	* sysdeps/unix/bsd/readdir.c: File removed.
Diffstat (limited to 'sysdeps/libm-ieee754/e_hypot.c')
-rw-r--r--sysdeps/libm-ieee754/e_hypot.c128
1 files changed, 128 insertions, 0 deletions
diff --git a/sysdeps/libm-ieee754/e_hypot.c b/sysdeps/libm-ieee754/e_hypot.c
new file mode 100644
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+++ b/sysdeps/libm-ieee754/e_hypot.c
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+/* @(#)e_hypot.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: e_hypot.c,v 1.9 1995/05/12 04:57:27 jtc Exp $";
+#endif
+
+/* __ieee754_hypot(x,y)
+ *
+ * Method :                  
+ *	If (assume round-to-nearest) z=x*x+y*y 
+ *	has error less than sqrt(2)/2 ulp, than 
+ *	sqrt(z) has error less than 1 ulp (exercise).
+ *
+ *	So, compute sqrt(x*x+y*y) with some care as 
+ *	follows to get the error below 1 ulp:
+ *
+ *	Assume x>y>0;
+ *	(if possible, set rounding to round-to-nearest)
+ *	1. if x > 2y  use
+ *		x1*x1+(y*y+(x2*(x+x1))) for x*x+y*y
+ *	where x1 = x with lower 32 bits cleared, x2 = x-x1; else
+ *	2. if x <= 2y use
+ *		t1*y1+((x-y)*(x-y)+(t1*y2+t2*y))
+ *	where t1 = 2x with lower 32 bits cleared, t2 = 2x-t1, 
+ *	y1= y with lower 32 bits chopped, y2 = y-y1.
+ *		
+ *	NOTE: scaling may be necessary if some argument is too 
+ *	      large or too tiny
+ *
+ * Special cases:
+ *	hypot(x,y) is INF if x or y is +INF or -INF; else
+ *	hypot(x,y) is NAN if x or y is NAN.
+ *
+ * Accuracy:
+ * 	hypot(x,y) returns sqrt(x^2+y^2) with error less 
+ * 	than 1 ulps (units in the last place) 
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+	double __ieee754_hypot(double x, double y)
+#else
+	double __ieee754_hypot(x,y)
+	double x, y;
+#endif
+{
+	double a=x,b=y,t1,t2,y1,y2,w;
+	int32_t j,k,ha,hb;
+
+	GET_HIGH_WORD(ha,x);
+	ha &= 0x7fffffff;
+	GET_HIGH_WORD(hb,y);
+	hb &= 0x7fffffff;
+	if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
+	SET_HIGH_WORD(a,ha);	/* a <- |a| */
+	SET_HIGH_WORD(b,hb);	/* b <- |b| */
+	if((ha-hb)>0x3c00000) {return a+b;} /* x/y > 2**60 */
+	k=0;
+	if(ha > 0x5f300000) {	/* a>2**500 */
+	   if(ha >= 0x7ff00000) {	/* Inf or NaN */
+	       u_int32_t low;
+	       w = a+b;			/* for sNaN */
+	       GET_LOW_WORD(low,a);
+	       if(((ha&0xfffff)|low)==0) w = a;
+	       GET_LOW_WORD(low,b);
+	       if(((hb^0x7ff00000)|low)==0) w = b;
+	       return w;
+	   }
+	   /* scale a and b by 2**-600 */
+	   ha -= 0x25800000; hb -= 0x25800000;	k += 600;
+	   SET_HIGH_WORD(a,ha);
+	   SET_HIGH_WORD(b,hb);
+	}
+	if(hb < 0x20b00000) {	/* b < 2**-500 */
+	    if(hb <= 0x000fffff) {	/* subnormal b or 0 */	
+	        u_int32_t low;
+		GET_LOW_WORD(low,b);
+		if((hb|low)==0) return a;
+		t1=0;
+		SET_HIGH_WORD(t1,0x7fd00000);	/* t1=2^1022 */
+		b *= t1;
+		a *= t1;
+		k -= 1022;
+	    } else {		/* scale a and b by 2^600 */
+	        ha += 0x25800000; 	/* a *= 2^600 */
+		hb += 0x25800000;	/* b *= 2^600 */
+		k -= 600;
+		SET_HIGH_WORD(a,ha);
+		SET_HIGH_WORD(b,hb);
+	    }
+	}
+    /* medium size a and b */
+	w = a-b;
+	if (w>b) {
+	    t1 = 0;
+	    SET_HIGH_WORD(t1,ha);
+	    t2 = a-t1;
+	    w  = __ieee754_sqrt(t1*t1-(b*(-b)-t2*(a+t1)));
+	} else {
+	    a  = a+a;
+	    y1 = 0;
+	    SET_HIGH_WORD(y1,hb);
+	    y2 = b - y1;
+	    t1 = 0;
+	    SET_HIGH_WORD(t1,ha+0x00100000);
+	    t2 = a - t1;
+	    w  = __ieee754_sqrt(t1*y1-(w*(-w)-(t1*y2+t2*b)));
+	}
+	if(k!=0) {
+	    u_int32_t high;
+	    t1 = 1.0;
+	    GET_HIGH_WORD(high,t1);
+	    SET_HIGH_WORD(t1,high+(k<<20));
+	    return t1*w;
+	} else return w;
+}