Return to dlapy2.f CVS log

Up to [local] / rpl / lapack / lapack

Annotation of rpl/lapack/lapack/dlapy2.f, revision 1.14

1.11      bertrand    1: *> \brief \b DLAPY2 returns sqrt(x2+y2).
1.8       bertrand    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: *
1.11      bertrand   59: *> \date September 2012
1.8       bertrand   60: *
                     61: *> \ingroup auxOTHERauxiliary
                     62: *
                     63: *  =====================================================================
1.1       bertrand   64:       DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
                     65: *
1.11      bertrand   66: *  -- LAPACK auxiliary routine (version 3.4.2) --
1.1       bertrand   67: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                     68: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.11      bertrand   69: *     September 2012
1.1       bertrand   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