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Annotation of rpl/lapack/lapack/izmax1.f, revision 1.12

1.12    ! bertrand    1: *> \brief \b IZMAX1 finds the index of the vector element whose real part has maximum absolute value.
1.9       bertrand    2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
                      5: * Online html documentation available at 
                      6: *            http://www.netlib.org/lapack/explore-html/ 
                      7: *
                      8: *> \htmlonly
                      9: *> Download IZMAX1 + dependencies 
                     10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/izmax1.f"> 
                     11: *> [TGZ]</a> 
                     12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/izmax1.f"> 
                     13: *> [ZIP]</a> 
                     14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/izmax1.f"> 
                     15: *> [TXT]</a>
                     16: *> \endhtmlonly 
                     17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
                     21: *       INTEGER          FUNCTION IZMAX1( N, CX, INCX )
                     22: * 
                     23: *       .. Scalar Arguments ..
                     24: *       INTEGER            INCX, N
                     25: *       ..
                     26: *       .. Array Arguments ..
                     27: *       COMPLEX*16         CX( * )
                     28: *       ..
                     29: *  
                     30: *
                     31: *> \par Purpose:
                     32: *  =============
                     33: *>
                     34: *> \verbatim
                     35: *>
                     36: *> IZMAX1 finds the index of the element whose real part has maximum
                     37: *> absolute value.
                     38: *>
                     39: *> Based on IZAMAX from Level 1 BLAS.
                     40: *> The change is to use the 'genuine' absolute value.
                     41: *> \endverbatim
                     42: *
                     43: *  Arguments:
                     44: *  ==========
                     45: *
                     46: *> \param[in] N
                     47: *> \verbatim
                     48: *>          N is INTEGER
                     49: *>          The number of elements in the vector CX.
                     50: *> \endverbatim
                     51: *>
                     52: *> \param[in] CX
                     53: *> \verbatim
                     54: *>          CX is COMPLEX*16 array, dimension (N)
                     55: *>          The vector whose elements will be summed.
                     56: *> \endverbatim
                     57: *>
                     58: *> \param[in] INCX
                     59: *> \verbatim
                     60: *>          INCX is INTEGER
                     61: *>          The spacing between successive values of CX.  INCX >= 1.
                     62: *> \endverbatim
                     63: *
                     64: *  Authors:
                     65: *  ========
                     66: *
                     67: *> \author Univ. of Tennessee 
                     68: *> \author Univ. of California Berkeley 
                     69: *> \author Univ. of Colorado Denver 
                     70: *> \author NAG Ltd. 
                     71: *
1.12    ! bertrand   72: *> \date September 2012
1.9       bertrand   73: *
                     74: *> \ingroup complex16OTHERauxiliary
                     75: *
                     76: *> \par Contributors:
                     77: *  ==================
                     78: *>
                     79: *> Nick Higham for use with ZLACON.
                     80: *
                     81: *  =====================================================================
1.1       bertrand   82:       INTEGER          FUNCTION IZMAX1( N, CX, INCX )
                     83: *
1.12    ! bertrand   84: *  -- LAPACK auxiliary routine (version 3.4.2) --
1.1       bertrand   85: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                     86: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.12    ! bertrand   87: *     September 2012
1.1       bertrand   88: *
                     89: *     .. Scalar Arguments ..
                     90:       INTEGER            INCX, N
                     91: *     ..
                     92: *     .. Array Arguments ..
                     93:       COMPLEX*16         CX( * )
                     94: *     ..
                     95: *
                     96: * =====================================================================
                     97: *
                     98: *     .. Local Scalars ..
                     99:       INTEGER            I, IX
                    100:       DOUBLE PRECISION   SMAX
                    101:       COMPLEX*16         ZDUM
                    102: *     ..
                    103: *     .. Intrinsic Functions ..
                    104:       INTRINSIC          ABS
                    105: *     ..
                    106: *     .. Statement Functions ..
                    107:       DOUBLE PRECISION   CABS1
                    108: *     ..
                    109: *     .. Statement Function definitions ..
                    110: *
                    111: *     NEXT LINE IS THE ONLY MODIFICATION.
                    112:       CABS1( ZDUM ) = ABS( ZDUM )
                    113: *     ..
                    114: *     .. Executable Statements ..
                    115: *
                    116:       IZMAX1 = 0
                    117:       IF( N.LT.1 )
                    118:      $   RETURN
                    119:       IZMAX1 = 1
                    120:       IF( N.EQ.1 )
                    121:      $   RETURN
                    122:       IF( INCX.EQ.1 )
                    123:      $   GO TO 30
                    124: *
                    125: *     CODE FOR INCREMENT NOT EQUAL TO 1
                    126: *
                    127:       IX = 1
                    128:       SMAX = CABS1( CX( 1 ) )
                    129:       IX = IX + INCX
                    130:       DO 20 I = 2, N
                    131:          IF( CABS1( CX( IX ) ).LE.SMAX )
                    132:      $      GO TO 10
                    133:          IZMAX1 = I
                    134:          SMAX = CABS1( CX( IX ) )
                    135:    10    CONTINUE
                    136:          IX = IX + INCX
                    137:    20 CONTINUE
                    138:       RETURN
                    139: *
                    140: *     CODE FOR INCREMENT EQUAL TO 1
                    141: *
                    142:    30 CONTINUE
                    143:       SMAX = CABS1( CX( 1 ) )
                    144:       DO 40 I = 2, N
                    145:          IF( CABS1( CX( I ) ).LE.SMAX )
                    146:      $      GO TO 40
                    147:          IZMAX1 = I
                    148:          SMAX = CABS1( CX( I ) )
                    149:    40 CONTINUE
                    150:       RETURN
                    151: *
                    152: *     End of IZMAX1
                    153: *
                    154:       END