slapy3()

real function slapy3	(	real	x,
		real	y,
		real	z
	)

SLAPY3 returns sqrt(x2+y2+z2).

Download SLAPY3 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 SLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
 unnecessary overflow and unnecessary underflow.

Parameters

[in]	X	X is REAL
[in]	Y	Y is REAL
[in]	Z	Z is REAL X, Y and Z specify the values x, y and z.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 67 of file slapy3.f.

*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      REAL               X, Y, Z
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO
      parameter( zero = 0.0e0 )
*     ..
*     .. Local Scalars ..
      REAL               W, XABS, YABS, ZABS, HUGEVAL
*     ..
*     .. External Subroutines ..
      REAL               SLAMCH
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          abs, max, sqrt
*     ..
*     .. Executable Statements ..
*
      hugeval = slamch( 'Overflow' )
      xabs = abs( x )
      yabs = abs( y )
      zabs = abs( z )
      w = max( xabs, yabs, zabs )
      IF( w.EQ.zero .OR. w.GT.hugeval ) THEN
*     W can be zero for max(0,nan,0)
*     adding all three entries together will make sure
*     NaN will not disappear.
         slapy3 =  xabs + yabs + zabs
      ELSE
         slapy3 = w*sqrt( ( xabs / w )**2+( yabs / w )**2+
     $            ( zabs / w )**2 )
      END IF
      RETURN
*
*     End of SLAPY3
*

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