hypot.c File Reference

#include <precomp.h>

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Macros
#define	__SQRT_DBL_MAX   1.3e+154
#define	__SQRT_DBL_MIN   2.3e-162

Functions
double	_hypot (double x, double y)

Macro Definition Documentation

__SQRT_DBL_MAX

#define __SQRT_DBL_MAX   1.3e+154

Definition at line 27 of file hypot.c.

__SQRT_DBL_MIN

#define __SQRT_DBL_MIN   2.3e-162

Definition at line 28 of file hypot.c.

Function Documentation

_hypot()

double _hypot	(	double	x,
		double	y
	)

Definition at line 34 of file hypot.c.

{
  double abig = fabs(x), asmall = fabs(y);
  double ratio;
 
  /* Make abig = max(|x|, |y|), asmall = min(|x|, |y|).  */
  if (abig < asmall)
    {
      double temp = abig;
 
      abig = asmall;
      asmall = temp;
    }
 
  /* Trivial case.  */
  if (asmall == 0.)
    return abig;
 
  /* Scale the numbers as much as possible by using its ratio.
     For example, if both ABIG and ASMALL are VERY small, then
     X^2 + Y^2 might be VERY inaccurate due to loss of
     significant digits.  Dividing ASMALL by ABIG scales them
     to a certain degree, so that accuracy is better.  */
 
  if ((ratio = asmall / abig) > __SQRT_DBL_MIN && abig < __SQRT_DBL_MAX)
    return abig * sqrt(1.0 + ratio*ratio);
  else
    {
      /* Slower but safer algorithm due to Moler and Morrison.  Never
         produces any intermediate result greater than roughly the
         larger of X and Y.  Should converge to machine-precision
         accuracy in 3 iterations.  */
 
      double r = ratio*ratio, t, s, p = abig, q = asmall;
 
      do {
        t = 4. + r;
        if (t == 4.)
          break;
        s = r / t;
        p += 2. * s * p;
        q *= s;
        r = (q / p) * (q / p);
      } while (1);
 
      return p;
    }
}