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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/s_cbrt.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/s_cbrt.c')
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diff --git a/sysdeps/libm-ieee754/s_cbrt.c b/sysdeps/libm-ieee754/s_cbrt.c
new file mode 100644
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+/* @(#)s_cbrt.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: s_cbrt.c,v 1.8 1995/05/10 20:46:49 jtc Exp $";
+#endif
+
+#include "math.h"
+#include "math_private.h"
+
+/* cbrt(x)
+ * Return cube root of x
+ */
+#ifdef __STDC__
+static const u_int32_t
+#else
+static u_int32_t
+#endif
+ B1 = 715094163, /* B1 = (682-0.03306235651)*2**20 */
+ B2 = 696219795; /* B2 = (664-0.03306235651)*2**20 */
+
+#ifdef __STDC__
+static const double
+#else
+static double
+#endif
+C = 5.42857142857142815906e-01, /* 19/35 = 0x3FE15F15, 0xF15F15F1 */
+D = -7.05306122448979611050e-01, /* -864/1225 = 0xBFE691DE, 0x2532C834 */
+E = 1.41428571428571436819e+00, /* 99/70 = 0x3FF6A0EA, 0x0EA0EA0F */
+F = 1.60714285714285720630e+00, /* 45/28 = 0x3FF9B6DB, 0x6DB6DB6E */
+G = 3.57142857142857150787e-01; /* 5/14 = 0x3FD6DB6D, 0xB6DB6DB7 */
+
+#ifdef __STDC__
+ double __cbrt(double x)
+#else
+ double __cbrt(x)
+ double x;
+#endif
+{
+ int32_t hx;
+ double r,s,t=0.0,w;
+ u_int32_t sign;
+ u_int32_t high,low;
+
+ GET_HIGH_WORD(hx,x);
+ sign=hx&0x80000000; /* sign= sign(x) */
+ hx ^=sign;
+ if(hx>=0x7ff00000) return(x+x); /* cbrt(NaN,INF) is itself */
+ GET_LOW_WORD(low,x);
+ if((hx|low)==0)
+ return(x); /* cbrt(0) is itself */
+
+ SET_HIGH_WORD(x,hx); /* x <- |x| */
+ /* rough cbrt to 5 bits */
+ if(hx<0x00100000) /* subnormal number */
+ {SET_HIGH_WORD(t,0x43500000); /* set t= 2**54 */
+ t*=x; GET_HIGH_WORD(high,t); SET_HIGH_WORD(t,high/3+B2);
+ }
+ else
+ SET_HIGH_WORD(t,hx/3+B1);
+
+
+ /* new cbrt to 23 bits, may be implemented in single precision */
+ r=t*t/x;
+ s=C+r*t;
+ t*=G+F/(s+E+D/s);
+
+ /* chopped to 20 bits and make it larger than cbrt(x) */
+ GET_HIGH_WORD(high,t);
+ INSERT_WORDS(t,high+0x00000001,0);
+
+
+ /* one step newton iteration to 53 bits with error less than 0.667 ulps */
+ s=t*t; /* t*t is exact */
+ r=x/s;
+ w=t+t;
+ r=(r-t)/(w+r); /* r-s is exact */
+ t=t+t*r;
+
+ /* retore the sign bit */
+ GET_HIGH_WORD(high,t);
+ SET_HIGH_WORD(t,high|sign);
+ return(t);
+}
+weak_alias (__cbrt, cbrt)