0,0 → 1,94 |
/* 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(!FLT_UWORD_IS_FINITE(hx)) |
return(x+x); /* cbrt(NaN,INF) is itself */ |
if(FLT_UWORD_IS_ZERO(hx)) |
return(x); /* cbrt(0) is itself */ |
|
SET_FLOAT_WORD(x,hx); /* x <- |x| */ |
/* rough cbrt to 5 bits */ |
if(FLT_UWORD_IS_SUBNORMAL(hx)) /* 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); |
} |
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#ifdef _DOUBLE_IS_32BITS |
|
#ifdef __STDC__ |
double cbrt(double x) |
#else |
double cbrt(x) |
double x; |
#endif |
{ |
return (double) cbrtf((float) x); |
} |
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#endif /* defined(_DOUBLE_IS_32BITS) */ |