source: pacpussensors/trunk/Vislab/lib3dv-1.2.0/lib3dv/eigen/lapack/dlapy2.f

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1*> \brief \b DLAPY2
2*
3* =========== DOCUMENTATION ===========
4*
5* Online html documentation available at
6* http://www.netlib.org/lapack/explore-html/
7*
8*> \htmlonly
9*> Download DLAPY2 + dependencies
10*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlapy2.f">
11*> [TGZ]</a>
12*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlapy2.f">
13*> [ZIP]</a>
14*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlapy2.f">
15*> [TXT]</a>
16*> \endhtmlonly
17*
18* Definition:
19* ===========
20*
21* DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
22*
23* .. Scalar Arguments ..
24* DOUBLE PRECISION X, Y
25* ..
26*
27*
28*> \par Purpose:
29* =============
30*>
31*> \verbatim
32*>
33*> DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
34*> overflow.
35*> \endverbatim
36*
37* Arguments:
38* ==========
39*
40*> \param[in] X
41*> \verbatim
42*> X is DOUBLE PRECISION
43*> \endverbatim
44*>
45*> \param[in] Y
46*> \verbatim
47*> Y is DOUBLE PRECISION
48*> X and Y specify the values x and y.
49*> \endverbatim
50*
51* Authors:
52* ========
53*
54*> \author Univ. of Tennessee
55*> \author Univ. of California Berkeley
56*> \author Univ. of Colorado Denver
57*> \author NAG Ltd.
58*
59*> \date November 2011
60*
61*> \ingroup auxOTHERauxiliary
62*
63* =====================================================================
64 DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
65*
66* -- LAPACK auxiliary routine (version 3.4.0) --
67* -- LAPACK is a software package provided by Univ. of Tennessee, --
68* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
69* November 2011
70*
71* .. Scalar Arguments ..
72 DOUBLE PRECISION X, Y
73* ..
74*
75* =====================================================================
76*
77* .. Parameters ..
78 DOUBLE PRECISION ZERO
79 PARAMETER ( ZERO = 0.0D0 )
80 DOUBLE PRECISION ONE
81 PARAMETER ( ONE = 1.0D0 )
82* ..
83* .. Local Scalars ..
84 DOUBLE PRECISION W, XABS, YABS, Z
85* ..
86* .. Intrinsic Functions ..
87 INTRINSIC ABS, MAX, MIN, SQRT
88* ..
89* .. Executable Statements ..
90*
91 XABS = ABS( X )
92 YABS = ABS( Y )
93 W = MAX( XABS, YABS )
94 Z = MIN( XABS, YABS )
95 IF( Z.EQ.ZERO ) THEN
96 DLAPY2 = W
97 ELSE
98 DLAPY2 = W*SQRT( ONE+( Z / W )**2 )
99 END IF
100 RETURN
101*
102* End of DLAPY2
103*
104 END
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