slapy2()

real function slapy2	(	real	x,
		real	y )

SLAPY2 returns sqrt(x2+y2).

Download SLAPY2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!> SLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
!> overflow and unnecessary underflow.
!> 

Parameters

[in]	X	!> X is REAL !>
[in]	Y	!> Y is REAL !> X and Y specify the values x and y. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 60 of file slapy2.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
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO
      parameter( zero = 0.0e0 )
      REAL               ONE
      parameter( one = 1.0e0 )
*     ..
*     .. Local Scalars ..
      REAL               W, XABS, YABS, Z, HUGEVAL
      LOGICAL            X_IS_NAN, Y_IS_NAN
*     ..
*     .. External Functions ..
      LOGICAL            SISNAN
      EXTERNAL           sisnan
*     ..
*     .. External Subroutines ..
      REAL               SLAMCH
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          abs, max, min, sqrt
*     ..
*     .. Executable Statements ..
*
      x_is_nan = sisnan( x )
      y_is_nan = sisnan( y )
      IF ( x_is_nan ) slapy2 = x
      IF ( y_is_nan ) slapy2 = y
      hugeval = slamch( 'Overflow' )
*
      IF ( .NOT.( x_is_nan.OR.y_is_nan ) ) THEN
         xabs = abs( x )
         yabs = abs( y )
         w = max( xabs, yabs )
         z = min( xabs, yabs )
         IF( z.EQ.zero .OR. w.GT.hugeval ) THEN
            slapy2 = w
         ELSE
            slapy2 = w*sqrt( one+( z / w )**2 )
         END IF
      END IF
      RETURN
*
*     End of SLAPY2
*

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