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1 *> \brief \b SLAPY3
3 * =========== DOCUMENTATION ===========
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
8 *> \htmlonly
9 *> Download SLAPY3 + dependencies
10 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slapy3.f">
11 *> [TGZ]</a>
12 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slapy3.f">
13 *> [ZIP]</a>
14 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slapy3.f">
15 *> [TXT]</a>
16 *> \endhtmlonly
18 * Definition:
19 * ===========
21 * REAL FUNCTION SLAPY3( X, Y, Z )
23 * .. Scalar Arguments ..
24 * REAL X, Y, Z
25 * ..
28 *> \par Purpose:
29 * =============
31 *> \verbatim
33 *> SLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
34 *> unnecessary overflow.
35 *> \endverbatim
37 * Arguments:
38 * ==========
40 *> \param[in] X
41 *> \verbatim
42 *> X is REAL
43 *> \endverbatim
45 *> \param[in] Y
46 *> \verbatim
47 *> Y is REAL
48 *> \endverbatim
50 *> \param[in] Z
51 *> \verbatim
52 *> Z is REAL
53 *> X, Y and Z specify the values x, y and z.
54 *> \endverbatim
56 * Authors:
57 * ========
59 *> \author Univ. of Tennessee
60 *> \author Univ. of California Berkeley
61 *> \author Univ. of Colorado Denver
62 *> \author NAG Ltd.
64 *> \date November 2011
66 *> \ingroup auxOTHERauxiliary
68 * =====================================================================
69 REAL FUNCTION SLAPY3( X, Y, Z )
71 * -- LAPACK auxiliary routine (version 3.4.0) --
72 * -- LAPACK is a software package provided by Univ. of Tennessee, --
73 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
74 * November 2011
76 * .. Scalar Arguments ..
77 REAL X, Y, Z
78 * ..
80 * =====================================================================
82 * .. Parameters ..
83 REAL ZERO
84 PARAMETER ( ZERO = 0.0E0 )
85 * ..
86 * .. Local Scalars ..
87 REAL W, XABS, YABS, ZABS
88 * ..
89 * .. Intrinsic Functions ..
90 INTRINSIC ABS, MAX, SQRT
91 * ..
92 * .. Executable Statements ..
94 XABS = ABS( X )
95 YABS = ABS( Y )
96 ZABS = ABS( Z )
97 W = MAX( XABS, YABS, ZABS )
98 IF( W.EQ.ZERO ) THEN
99 * W can be zero for max(0,nan,0)
100 * adding all three entries together will make sure
101 * NaN will not disappear.
102 SLAPY3 = XABS + YABS + ZABS
103 ELSE
104 SLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
105 $ ( ZABS / W )**2 )
106 END IF
107 RETURN
109 * End of SLAPY3