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Annotation of rpl/lapack/lapack/dladiv.f, revision 1.12

1.11      bertrand    1: *> \brief \b DLADIV performs complex division in real arithmetic, avoiding unnecessary overflow.
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 DLADIV + dependencies 
                     10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dladiv.f"> 
                     11: *> [TGZ]</a> 
                     12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dladiv.f"> 
                     13: *> [ZIP]</a> 
                     14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dladiv.f"> 
                     15: *> [TXT]</a>
                     16: *> \endhtmlonly 
                     17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
                     21: *       SUBROUTINE DLADIV( A, B, C, D, P, Q )
                     22: * 
                     23: *       .. Scalar Arguments ..
                     24: *       DOUBLE PRECISION   A, B, C, D, P, Q
                     25: *       ..
                     26: *  
                     27: *
                     28: *> \par Purpose:
                     29: *  =============
                     30: *>
                     31: *> \verbatim
                     32: *>
                     33: *> DLADIV performs complex division in  real arithmetic
                     34: *>
                     35: *>                       a + i*b
                     36: *>            p + i*q = ---------
                     37: *>                       c + i*d
                     38: *>
                     39: *> The algorithm is due to Robert L. Smith and can be found
                     40: *> in D. Knuth, The art of Computer Programming, Vol.2, p.195
                     41: *> \endverbatim
                     42: *
                     43: *  Arguments:
                     44: *  ==========
                     45: *
                     46: *> \param[in] A
                     47: *> \verbatim
                     48: *>          A is DOUBLE PRECISION
                     49: *> \endverbatim
                     50: *>
                     51: *> \param[in] B
                     52: *> \verbatim
                     53: *>          B is DOUBLE PRECISION
                     54: *> \endverbatim
                     55: *>
                     56: *> \param[in] C
                     57: *> \verbatim
                     58: *>          C is DOUBLE PRECISION
                     59: *> \endverbatim
                     60: *>
                     61: *> \param[in] D
                     62: *> \verbatim
                     63: *>          D is DOUBLE PRECISION
                     64: *>          The scalars a, b, c, and d in the above expression.
                     65: *> \endverbatim
                     66: *>
                     67: *> \param[out] P
                     68: *> \verbatim
                     69: *>          P is DOUBLE PRECISION
                     70: *> \endverbatim
                     71: *>
                     72: *> \param[out] Q
                     73: *> \verbatim
                     74: *>          Q is DOUBLE PRECISION
                     75: *>          The scalars p and q in the above expression.
                     76: *> \endverbatim
                     77: *
                     78: *  Authors:
                     79: *  ========
                     80: *
                     81: *> \author Univ. of Tennessee 
                     82: *> \author Univ. of California Berkeley 
                     83: *> \author Univ. of Colorado Denver 
                     84: *> \author NAG Ltd. 
                     85: *
1.11      bertrand   86: *> \date September 2012
1.8       bertrand   87: *
                     88: *> \ingroup auxOTHERauxiliary
                     89: *
                     90: *  =====================================================================
1.1       bertrand   91:       SUBROUTINE DLADIV( A, B, C, D, P, Q )
                     92: *
1.11      bertrand   93: *  -- LAPACK auxiliary routine (version 3.4.2) --
1.1       bertrand   94: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                     95: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.11      bertrand   96: *     September 2012
1.1       bertrand   97: *
                     98: *     .. Scalar Arguments ..
                     99:       DOUBLE PRECISION   A, B, C, D, P, Q
                    100: *     ..
                    101: *
                    102: *  =====================================================================
                    103: *
                    104: *     .. Local Scalars ..
                    105:       DOUBLE PRECISION   E, F
                    106: *     ..
                    107: *     .. Intrinsic Functions ..
                    108:       INTRINSIC          ABS
                    109: *     ..
                    110: *     .. Executable Statements ..
                    111: *
                    112:       IF( ABS( D ).LT.ABS( C ) ) THEN
                    113:          E = D / C
                    114:          F = C + D*E
                    115:          P = ( A+B*E ) / F
                    116:          Q = ( B-A*E ) / F
                    117:       ELSE
                    118:          E = C / D
                    119:          F = D + C*E
                    120:          P = ( B+A*E ) / F
                    121:          Q = ( -A+B*E ) / F
                    122:       END IF
                    123: *
                    124:       RETURN
                    125: *
                    126: *     End of DLADIV
                    127: *
                    128:       END