Subversion Repositories openrisc_2011-10-31

/*

 * ====================================================

 * 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.

 * ====================================================

*/

#ifndef __vax__

static const unsigned long

        B1 = 715094163, /* B1 = (682-0.03306235651)*2**20 */

        B2 = 696219795; /* B2 = (664-0.03306235651)*2**20 */

static const double

        C =  5.42857142857142815906e-01, /* 19/35     = 0x3FE15F15, 0xF15F15F1 */

        D = -7.05306122448979611050e-01, /* -864/1225 = 0xBFE691DE, 0x2532C834 */

        E =  1.41428571428571436819e+00, /* 99/70     = 0x3FF6A0EA, 0x0EA0EA0F */

        F =  1.60714285714285720630e+00, /* 45/28     = 0x3FF9B6DB, 0x6DB6DB6E */

        G =  3.57142857142857150787e-01; /* 5/14      = 0x3FD6DB6D, 0xB6DB6DB7 */

double

cbrtl (double x)

{

  long hx;

  double r,s,w;

  double lt;

  unsigned sign;

  typedef unsigned unsigned32 __attribute__((mode(SI)));

  union {

    double t;

    unsigned32 pt[2];

  } ut, ux;

  int n0;

  ut.t = 1.0;

  n0 = (ut.pt[0] == 0);

  ut.t = 0.0;

  ux.t = x;

  hx = ux.pt[n0];                       /* high word of x */

  sign=hx&0x80000000;                   /* sign= sign(x) */

  hx  ^=sign;

  if(hx>=0x7ff00000) return(x+x);       /* cbrt(NaN,INF) is itself */

  if((hx| ux.pt[1-n0])==0)

    return(ux.t);                       /* cbrt(0) is itself */

  ux.pt[n0] = hx;

  /* rough cbrt to 5 bits */

  if(hx<0x00100000)                     /* subnormal number */

    {ut.pt[n0]=0x43500000;              /* set t= 2**54 */

     ut.t*=x; ut.pt[n0]=ut.pt[n0]/3+B2;

   }

  else

    ut.pt[n0]=hx/3+B1;

  /* new cbrt to 23 bits, may be implemented in single precision */

  r=ut.t*ut.t/ux.t;

  s=C+r*ut.t;

  ut.t*=G+F/(s+E+D/s);

  /* chopped to 20 bits and make it larger than cbrt(x) */

  ut.pt[1-n0]=0; ut.pt[n0]+=0x00000001;

  /* one step newton iteration to 53 bits with error less than 0.667 ulps */

  s=ut.t*ut.t;                          /* t*t is exact */

  r=ux.t/s;

  w=ut.t+ut.t;

  r=(r-ut.t)/(w+r);                     /* r-s is exact */

  ut.t=ut.t+ut.t*r;

  /* restore the sign bit */

  ut.pt[n0] |= sign;

  lt = ut.t;

  lt -= (lt - (x/(lt*lt))) * 0.333333333333333333333;

  return lt;

}

main ()

{

  if ((int) (cbrtl (27.0) + 0.5) != 3)

    abort ();

  exit (0);

}

#else

main () { exit (0); }

#endif