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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) */