1 /* s_cbrtf.c -- float version of s_cbrt.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
13 * ====================================================
17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_cbrtf.c,v 1.5 1999/08/28 00:06:44 peter Exp $";
21 #include "math_private.h"
24 * Return cube root of x
31 B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */
32 B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */
39 C = 5.4285717010e-01, /* 19/35 = 0x3f0af8b0 */
40 D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
41 E = 1.4142856598e+00, /* 99/70 = 0x3fb50750 */
42 F = 1.6071428061e+00, /* 45/28 = 0x3fcdb6db */
43 G = 3.5714286566e-01; /* 5/14 = 0x3eb6db6e */
58 sign=hx&0x80000000; /* sign= sign(x) */
60 if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */
62 return(x); /* cbrt(0) is itself */
64 SET_FLOAT_WORD(x,hx); /* x <- |x| */
65 /* rough cbrt to 5 bits */
66 if(hx<0x00800000) /* subnormal number */
67 {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
68 t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2);
71 SET_FLOAT_WORD(t,hx/3+B1);
74 /* new cbrt to 23 bits */
79 /* retore the sign bit */
80 GET_FLOAT_WORD(high,t);
81 SET_FLOAT_WORD(t,high|sign);