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/* sf_cbrt.c -- float version of s_cbrt.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */
 
/*
 * ====================================================
 * 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.
 * ====================================================
 *
 */
 
#include "fdlibm.h"
 
/* cbrtf(x)
 * Return cube root of x
 */
#ifdef __STDC__
static const __uint32_t
#else
static __uint32_t
#endif
        B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */
        B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */
 
#ifdef __STDC__
static const float
#else
static float
#endif
C =  5.4285717010e-01, /* 19/35     = 0x3f0af8b0 */
D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
E =  1.4142856598e+00, /* 99/70     = 0x3fb50750 */
F =  1.6071428061e+00, /* 45/28     = 0x3fcdb6db */
G =  3.5714286566e-01; /* 5/14      = 0x3eb6db6e */
 
#ifdef __STDC__
        float cbrtf(float x)
#else
        float cbrtf(x)
        float x;
#endif
{
        __int32_t       hx;
        float r,s,t;
        __uint32_t sign;
        __uint32_t high;
 
        GET_FLOAT_WORD(hx,x);
        sign=hx&0x80000000;             /* sign= sign(x) */
        hx  ^=sign;
        if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */
        if(hx==0)
            return(x);          /* cbrt(0) is itself */
 
        SET_FLOAT_WORD(x,hx);   /* x <- |x| */
    /* rough cbrt to 5 bits */
        if(hx<0x00800000)               /* subnormal number */
          {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
           t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2);
          }
        else
          SET_FLOAT_WORD(t,hx/3+B1);
 
 
    /* new cbrt to 23 bits */
        r=t*t/x;
        s=C+r*t;
        t*=G+F/(s+E+D/s);
 
    /* retore the sign bit */
        GET_FLOAT_WORD(high,t);
        SET_FLOAT_WORD(t,high|sign);
        return(t);
}
 
#ifdef _DOUBLE_IS_32BITS
 
#ifdef __STDC__
        double cbrt(double x)
#else
        double cbrt(x)
        double x;
#endif
{
        return (double) cbrtf((float) x);
}
 
#endif /* defined(_DOUBLE_IS_32BITS) */

Line No.	Rev	Author	Line
1	56	joel	`/* sf_cbrt.c -- float version of s_cbrt.c.`
2			`* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.`
3			`*/`
4
5			`/*`
6			`* ====================================================`
7			`* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.`
8			`*`
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`
12			`* is preserved.`
13			`* ====================================================`
14			`*`
15			`*/`
16
17			`#include "fdlibm.h"`
18
19			`/* cbrtf(x)`
20			`* Return cube root of x`
21			`*/`
22			`#ifdef __STDC__`
23			`static const __uint32_t`
24			`#else`
25			`static __uint32_t`
26			`#endif`
27			`B1 = 709958130, /* B1 = (84+2/3-0.03306235651)223 /`
28			`B2 = 642849266; /* B2 = (76+2/3-0.03306235651)223 /`
29
30			`#ifdef __STDC__`
31			`static const float`
32			`#else`
33			`static float`
34			`#endif`
35			`C = 5.4285717010e-01, /* 19/35 = 0x3f0af8b0 */`
36			`D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */`
37			`E = 1.4142856598e+00, /* 99/70 = 0x3fb50750 */`
38			`F = 1.6071428061e+00, /* 45/28 = 0x3fcdb6db */`
39			`G = 3.5714286566e-01; /* 5/14 = 0x3eb6db6e */`
40
41			`#ifdef __STDC__`
42			`float cbrtf(float x)`
43			`#else`
44			`float cbrtf(x)`
45			`float x;`
46			`#endif`
47			`{`
48			`__int32_t hx;`
49			`float r,s,t;`
50			`__uint32_t sign;`
51			`__uint32_t high;`
52
53			`GET_FLOAT_WORD(hx,x);`
54			`sign=hx&0x80000000; /* sign= sign(x) */`
55			`hx ^=sign;`
56			`if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */`
57			`if(hx==0)`
58			`return(x); /* cbrt(0) is itself */`
59
60			`SET_FLOAT_WORD(x,hx); /* x <- \|x\| */`
61			`/* rough cbrt to 5 bits */`
62			`if(hx<0x00800000) /* subnormal number */`
63			`{SET_FLOAT_WORD(t,0x4b800000); /* set t= 2*24 /`
64			`t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2);`
65			`}`
66			`else`
67			`SET_FLOAT_WORD(t,hx/3+B1);`
68
69
70			`/* new cbrt to 23 bits */`
71			`r=t*t/x;`
72			`s=C+r*t;`
73			`t*=G+F/(s+E+D/s);`
74
75			`/* retore the sign bit */`
76			`GET_FLOAT_WORD(high,t);`
77			`SET_FLOAT_WORD(t,high\|sign);`
78			`return(t);`
79			`}`
80
81			`#ifdef _DOUBLE_IS_32BITS`
82
83			`#ifdef __STDC__`
84			`double cbrt(double x)`
85			`#else`
86			`double cbrt(x)`
87			`double x;`
88			`#endif`
89			`{`
90			`return (double) cbrtf((float) x);`
91			`}`
92
93			`#endif /* defined(_DOUBLE_IS_32BITS) */`

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