mirror of
https://gitlab.com/libeigen/eigen.git
synced 2024-12-09 07:00:27 +08:00
105 lines
2.5 KiB
Fortran
105 lines
2.5 KiB
Fortran
*> \brief \b DLAPY2
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
*> \htmlonly
|
|
*> Download DLAPY2 + dependencies
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlapy2.f">
|
|
*> [TGZ]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlapy2.f">
|
|
*> [ZIP]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlapy2.f">
|
|
*> [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
|