Chimie Théorique » Opt'n Path

      DOUBLE PRECISION FUNCTION DLAPY2( X, Y )

*

*  -- LAPACK auxiliary routine (version 3.2) --

*  -- LAPACK is a software package provided by Univ. of Tennessee,    --

*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--

*     November 2006

*

*     .. Scalar Arguments ..

      DOUBLE PRECISION   X, Y

*     ..

*

*  Purpose

*  =======

*

*  DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary

*  overflow.

*

*  Arguments

*  =========

*

*  X       (input) DOUBLE PRECISION

*  Y       (input) DOUBLE PRECISION

*          X and Y specify the values x and y.

*

*  =====================================================================

*

*     .. Parameters ..

      DOUBLE PRECISION   ZERO

      PARAMETER          ( ZERO = 0.0D0 )

      DOUBLE PRECISION   ONE

      PARAMETER          ( ONE = 1.0D0 )

*     ..

*     .. Local Scalars ..

      DOUBLE PRECISION   W, XABS, YABS, Z

*     ..

*     .. Intrinsic Functions ..

      INTRINSIC          ABS, MAX, MIN, SQRT

*     ..

*     .. Executable Statements ..

*

      XABS = ABS( X )

      YABS = ABS( Y )

      W = MAX( XABS, YABS )

      Z = MIN( XABS, YABS )

      IF( Z.EQ.ZERO ) THEN

         DLAPY2 = W

      ELSE

         DLAPY2 = W*SQRT( ONE+( Z / W )**2 )

      END IF

      RETURN

*

*     End of DLAPY2

*

      END