| /* 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); |
| } |
| |
| #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) */ |