| 1 | *> \brief \b DLAPY3
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| 2 | *
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| 3 | * =========== DOCUMENTATION ===========
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| 4 | *
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| 5 | * Online html documentation available at
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| 6 | * http://www.netlib.org/lapack/explore-html/
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| 7 | *
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| 8 | *> \htmlonly
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| 9 | *> Download DLAPY3 + dependencies
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| 10 | *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlapy3.f">
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| 11 | *> [TGZ]</a>
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| 12 | *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlapy3.f">
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| 13 | *> [ZIP]</a>
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| 14 | *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlapy3.f">
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| 15 | *> [TXT]</a>
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| 16 | *> \endhtmlonly
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| 17 | *
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| 18 | * Definition:
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| 19 | * ===========
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| 20 | *
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| 21 | * DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z )
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| 22 | *
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| 23 | * .. Scalar Arguments ..
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| 24 | * DOUBLE PRECISION X, Y, Z
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| 25 | * ..
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| 26 | *
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| 27 | *
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| 28 | *> \par Purpose:
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| 29 | * =============
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| 30 | *>
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| 31 | *> \verbatim
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| 32 | *>
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| 33 | *> DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
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| 34 | *> unnecessary overflow.
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| 35 | *> \endverbatim
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| 36 | *
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| 37 | * Arguments:
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| 38 | * ==========
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| 39 | *
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| 40 | *> \param[in] X
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| 41 | *> \verbatim
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| 42 | *> X is DOUBLE PRECISION
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| 43 | *> \endverbatim
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| 44 | *>
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| 45 | *> \param[in] Y
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| 46 | *> \verbatim
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| 47 | *> Y is DOUBLE PRECISION
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| 48 | *> \endverbatim
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| 49 | *>
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| 50 | *> \param[in] Z
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| 51 | *> \verbatim
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| 52 | *> Z is DOUBLE PRECISION
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| 53 | *> X, Y and Z specify the values x, y and z.
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| 54 | *> \endverbatim
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| 55 | *
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| 56 | * Authors:
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| 57 | * ========
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| 58 | *
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| 59 | *> \author Univ. of Tennessee
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| 60 | *> \author Univ. of California Berkeley
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| 61 | *> \author Univ. of Colorado Denver
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| 62 | *> \author NAG Ltd.
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| 63 | *
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| 64 | *> \date November 2011
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| 65 | *
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| 66 | *> \ingroup auxOTHERauxiliary
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| 67 | *
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| 68 | * =====================================================================
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| 69 | DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z )
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| 70 | *
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| 71 | * -- LAPACK auxiliary routine (version 3.4.0) --
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| 72 | * -- LAPACK is a software package provided by Univ. of Tennessee, --
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| 73 | * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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| 74 | * November 2011
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| 75 | *
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| 76 | * .. Scalar Arguments ..
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| 77 | DOUBLE PRECISION X, Y, Z
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| 78 | * ..
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| 79 | *
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| 80 | * =====================================================================
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| 81 | *
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| 82 | * .. Parameters ..
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| 83 | DOUBLE PRECISION ZERO
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| 84 | PARAMETER ( ZERO = 0.0D0 )
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| 85 | * ..
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| 86 | * .. Local Scalars ..
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| 87 | DOUBLE PRECISION W, XABS, YABS, ZABS
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| 88 | * ..
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| 89 | * .. Intrinsic Functions ..
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| 90 | INTRINSIC ABS, MAX, SQRT
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| 91 | * ..
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| 92 | * .. Executable Statements ..
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| 93 | *
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| 94 | XABS = ABS( X )
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| 95 | YABS = ABS( Y )
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| 96 | ZABS = ABS( Z )
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| 97 | W = MAX( XABS, YABS, ZABS )
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| 98 | IF( W.EQ.ZERO ) THEN
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| 99 | * W can be zero for max(0,nan,0)
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| 100 | * adding all three entries together will make sure
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| 101 | * NaN will not disappear.
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| 102 | DLAPY3 = XABS + YABS + ZABS
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| 103 | ELSE
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| 104 | DLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
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| 105 | $ ( ZABS / W )**2 )
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| 106 | END IF
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| 107 | RETURN
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| 108 | *
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| 109 | * End of DLAPY3
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| 110 | *
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| 111 | END
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