mirror of
https://gitlab.com/libeigen/eigen.git
synced 2024-12-27 07:29:52 +08:00
112 lines
2.6 KiB
Fortran
112 lines
2.6 KiB
Fortran
*> \brief \b SLAPY3
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
*> \htmlonly
|
|
*> Download SLAPY3 + dependencies
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slapy3.f">
|
|
*> [TGZ]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slapy3.f">
|
|
*> [ZIP]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slapy3.f">
|
|
*> [TXT]</a>
|
|
*> \endhtmlonly
|
|
*
|
|
* Definition:
|
|
* ===========
|
|
*
|
|
* REAL FUNCTION SLAPY3( X, Y, Z )
|
|
*
|
|
* .. Scalar Arguments ..
|
|
* REAL X, Y, Z
|
|
* ..
|
|
*
|
|
*
|
|
*> \par Purpose:
|
|
* =============
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> SLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
|
|
*> unnecessary overflow.
|
|
*> \endverbatim
|
|
*
|
|
* Arguments:
|
|
* ==========
|
|
*
|
|
*> \param[in] X
|
|
*> \verbatim
|
|
*> X is REAL
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] Y
|
|
*> \verbatim
|
|
*> Y is REAL
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] Z
|
|
*> \verbatim
|
|
*> Z is REAL
|
|
*> X, Y and Z specify the values x, y and z.
|
|
*> \endverbatim
|
|
*
|
|
* Authors:
|
|
* ========
|
|
*
|
|
*> \author Univ. of Tennessee
|
|
*> \author Univ. of California Berkeley
|
|
*> \author Univ. of Colorado Denver
|
|
*> \author NAG Ltd.
|
|
*
|
|
*> \date November 2011
|
|
*
|
|
*> \ingroup auxOTHERauxiliary
|
|
*
|
|
* =====================================================================
|
|
REAL FUNCTION SLAPY3( X, Y, Z )
|
|
*
|
|
* -- 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 ..
|
|
REAL X, Y, Z
|
|
* ..
|
|
*
|
|
* =====================================================================
|
|
*
|
|
* .. Parameters ..
|
|
REAL ZERO
|
|
PARAMETER ( ZERO = 0.0E0 )
|
|
* ..
|
|
* .. Local Scalars ..
|
|
REAL W, XABS, YABS, ZABS
|
|
* ..
|
|
* .. Intrinsic Functions ..
|
|
INTRINSIC ABS, MAX, SQRT
|
|
* ..
|
|
* .. Executable Statements ..
|
|
*
|
|
XABS = ABS( X )
|
|
YABS = ABS( Y )
|
|
ZABS = ABS( Z )
|
|
W = MAX( XABS, YABS, ZABS )
|
|
IF( W.EQ.ZERO ) THEN
|
|
* W can be zero for max(0,nan,0)
|
|
* adding all three entries together will make sure
|
|
* NaN will not disappear.
|
|
SLAPY3 = XABS + YABS + ZABS
|
|
ELSE
|
|
SLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
|
|
$ ( ZABS / W )**2 )
|
|
END IF
|
|
RETURN
|
|
*
|
|
* End of SLAPY3
|
|
*
|
|
END
|