dlapy3()

double precision function dlapy3	(	double precision	x,
		double precision	y,
		double precision	z )

DLAPY3 returns sqrt(x2+y2+z2).

Download DLAPY3 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!> DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
!> unnecessary overflow and unnecessary underflow.
!> 

Parameters

[in]	X	!> X is DOUBLE PRECISION !>
[in]	Y	!> Y is DOUBLE PRECISION !>
[in]	Z	!> Z is DOUBLE PRECISION !> 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 65 of file dlapy3.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 ..
      DOUBLE PRECISION   X, Y, Z
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   ZERO
      parameter( zero = 0.0d0 )
*     ..
*     .. Local Scalars ..
      DOUBLE PRECISION   W, XABS, YABS, ZABS, HUGEVAL
*     ..
*     .. External Subroutines ..
      DOUBLE PRECISION   DLAMCH
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          abs, max, sqrt
*     ..
*     .. Executable Statements ..
*
      hugeval = dlamch( '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.
         dlapy3 =  xabs + yabs + zabs
      ELSE
         dlapy3 = w*sqrt( ( xabs / w )**2+( yabs / w )**2+
     $            ( zabs / w )**2 )
      END IF
      RETURN
*
*     End of DLAPY3
*

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