118 lines
2.9 KiB
Fortran
118 lines
2.9 KiB
Fortran
*> \brief \b SLAPY2 returns sqrt(x2+y2).
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
*> \htmlonly
|
|
*> Download SLAPY2 + dependencies
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slapy2.f">
|
|
*> [TGZ]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slapy2.f">
|
|
*> [ZIP]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slapy2.f">
|
|
*> [TXT]</a>
|
|
*> \endhtmlonly
|
|
*
|
|
* Definition:
|
|
* ===========
|
|
*
|
|
* REAL FUNCTION SLAPY2( X, Y )
|
|
*
|
|
* .. Scalar Arguments ..
|
|
* REAL X, Y
|
|
* ..
|
|
*
|
|
*
|
|
*> \par Purpose:
|
|
* =============
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> SLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
|
|
*> overflow and unnecessary underflow.
|
|
*> \endverbatim
|
|
*
|
|
* Arguments:
|
|
* ==========
|
|
*
|
|
*> \param[in] X
|
|
*> \verbatim
|
|
*> X is REAL
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] Y
|
|
*> \verbatim
|
|
*> Y is REAL
|
|
*> 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.
|
|
*
|
|
*> \ingroup OTHERauxiliary
|
|
*
|
|
* =====================================================================
|
|
REAL FUNCTION SLAPY2( X, Y )
|
|
*
|
|
* -- 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
|
|
*
|
|
END
|