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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.17.0/] [newlib/] [libm/] [common/] [sf_cbrt.c] - Rev 527
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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(!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) */
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