lapack/dlapy2.f

*> \brief \b DLAPY2
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at 
*            http://www.netlib.org/lapack/explore-html/ 
*
*> \htmlonly
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*> [TXT]</a>
*> \endhtmlonly 
*
*  Definition:
*  ===========
*
*       DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
* 
*       .. Scalar Arguments ..
*       DOUBLE PRECISION   X, Y
*       ..
*  
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
*> overflow.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] X
*> \verbatim
*>          X is DOUBLE PRECISION
*> \endverbatim
*>
*> \param[in] Y
*> \verbatim
*>          Y is DOUBLE PRECISION
*>          X and Y specify the values x and y.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee 
*> \author Univ. of California Berkeley 
*> \author Univ. of Colorado Denver 
*> \author NAG Ltd. 
*
*> \date November 2011
*
*> \ingroup auxOTHERauxiliary
*
*  =====================================================================
      DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
*
*  -- LAPACK auxiliary routine (version 3.4.0) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2011
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION   X, 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