1 /* s_cbrtf.c -- float version of s_cbrt.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
4 * $FreeBSD: src/lib/msun/src/s_cbrtf.c,v 1.5 1999/08/28 00:06:44 peter Exp $
5 * $DragonFly: src/lib/msun/src/Attic/s_cbrtf.c,v 1.2 2003/06/17 04:26:53 dillon Exp $
9 * ====================================================
10 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
12 * Developed at SunPro, a Sun Microsystems, Inc. business.
13 * Permission to use, copy, modify, and distribute this
14 * software is freely granted, provided that this notice
16 * ====================================================
20 #include "math_private.h"
23 * Return cube root of x
30 B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */
31 B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */
38 C = 5.4285717010e-01, /* 19/35 = 0x3f0af8b0 */
39 D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
40 E = 1.4142856598e+00, /* 99/70 = 0x3fb50750 */
41 F = 1.6071428061e+00, /* 45/28 = 0x3fcdb6db */
42 G = 3.5714286566e-01; /* 5/14 = 0x3eb6db6e */
57 sign=hx&0x80000000; /* sign= sign(x) */
59 if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */
61 return(x); /* cbrt(0) is itself */
63 SET_FLOAT_WORD(x,hx); /* x <- |x| */
64 /* rough cbrt to 5 bits */
65 if(hx<0x00800000) /* subnormal number */
66 {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
67 t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2);
70 SET_FLOAT_WORD(t,hx/3+B1);
73 /* new cbrt to 23 bits */
78 /* retore the sign bit */
79 GET_FLOAT_WORD(high,t);
80 SET_FLOAT_WORD(t,high|sign);