Quelle s_rint.cpp Sprache: C

/* @(#)s_rint.c 5.1 93/09/24 */
/*
* ====================================================
* 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 <sys/cdefs.h>
//__FBSDID("$FreeBSD$");

/*
* rint(x)
* Return x rounded to integral value according to the prevailing
* rounding mode.
* Method:
* Using floating addition.
* Exception:
* Inexact flag raised if x not equal to rint(x).
*/

#include <float.h>

#include "math_private.h"

static const double
TWO52[2]={
  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
};

double
rint(double x)
{
int32_t i0,j0,sx;
u_int32_t i,i1;
double w,t;
EXTRACT_WORDS(i0,i1,x);
sx = (i0>>31)&1;
j0 = ((i0>>20)&0x7ff)-0x3ff;
if(j0<20) {
     if(j0<0) {
  if(((i0&0x7fffffff)|i1)==0) return x;
  i1 |= (i0&0x0fffff);
  i0 &= 0xfffe0000;
  i0 |= ((i1|-i1)>>12)&0x80000;
  SET_HIGH_WORD(x,i0);
         STRICT_ASSIGN(double,w,TWO52[sx]+x);
         t =  w-TWO52[sx];
  GET_HIGH_WORD(i0,t);
  SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
         return t;
     } else {
  i = (0x000fffff)>>j0;
  if(((i0&i)|i1)==0) return x; /* x is integral */
  i>>=1;
  if(((i0&i)|i1)!=0) {
      /*
     * Some bit is set after the 0.5 bit.  To avoid the
     * possibility of errors from double rounding in
     * w = TWO52[sx]+x, adjust the 0.25 bit to a lower
     * guard bit.  We do this for all j0<=51.  The
     * adjustment is trickiest for j0==18 and j0==19
     * since then it spans the word boundary.
     */
      if(j0==19) i1 = 0x40000000; else
      if(j0==18) i1 = 0x80000000; else
      i0 = (i0&(~i))|((0x20000)>>j0);
  }
     }
} else if (j0>51) {
     if(j0==0x400) return x+x; /* inf or NaN */
     else return x;  /* x is integral */
} else {
     i = ((u_int32_t)(0xffffffff))>>(j0-20);
     if((i1&i)==0) return x; /* x is integral */
     i>>=1;
     if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
}
INSERT_WORDS(x,i0,i1);
STRICT_ASSIGN(double,w,TWO52[sx]+x);
return w-TWO52[sx];
}

quality100%

¤ Dauer der Verarbeitung: 0.1 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.