| Carlos Hernandez | 7faaa9f | 2014-08-05 17:53:32 -0700 | [diff] [blame] | 1 | *> \brief \b SLAPY3 |
| 2 | * |
| 3 | * =========== DOCUMENTATION =========== |
| 4 | * |
| 5 | * Online html documentation available at |
| 6 | * http://www.netlib.org/lapack/explore-html/ |
| 7 | * |
| 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 |
| 17 | * |
| 18 | * Definition: |
| 19 | * =========== |
| 20 | * |
| 21 | * REAL FUNCTION SLAPY3( X, Y, Z ) |
| 22 | * |
| 23 | * .. Scalar Arguments .. |
| 24 | * REAL X, Y, Z |
| 25 | * .. |
| 26 | * |
| 27 | * |
| 28 | *> \par Purpose: |
| 29 | * ============= |
| 30 | *> |
| 31 | *> \verbatim |
| 32 | *> |
| 33 | *> SLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause |
| 34 | *> unnecessary overflow. |
| 35 | *> \endverbatim |
| 36 | * |
| 37 | * Arguments: |
| 38 | * ========== |
| 39 | * |
| 40 | *> \param[in] X |
| 41 | *> \verbatim |
| 42 | *> X is REAL |
| 43 | *> \endverbatim |
| 44 | *> |
| 45 | *> \param[in] Y |
| 46 | *> \verbatim |
| 47 | *> Y is REAL |
| 48 | *> \endverbatim |
| 49 | *> |
| 50 | *> \param[in] Z |
| 51 | *> \verbatim |
| 52 | *> Z is REAL |
| 53 | *> X, Y and Z specify the values x, y and z. |
| 54 | *> \endverbatim |
| 55 | * |
| 56 | * Authors: |
| 57 | * ======== |
| 58 | * |
| 59 | *> \author Univ. of Tennessee |
| 60 | *> \author Univ. of California Berkeley |
| 61 | *> \author Univ. of Colorado Denver |
| 62 | *> \author NAG Ltd. |
| 63 | * |
| 64 | *> \date November 2011 |
| 65 | * |
| 66 | *> \ingroup auxOTHERauxiliary |
| 67 | * |
| 68 | * ===================================================================== |
| 69 | REAL FUNCTION SLAPY3( X, Y, Z ) |
| 70 | * |
| 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 |
| 75 | * |
| 76 | * .. Scalar Arguments .. |
| 77 | REAL X, Y, Z |
| 78 | * .. |
| 79 | * |
| 80 | * ===================================================================== |
| 81 | * |
| 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 .. |
| 93 | * |
| 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 |
| 108 | * |
| 109 | * End of SLAPY3 |
| 110 | * |
| 111 | END |