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Annotation of rpl/lapack/lapack/izmax1.f, revision 1.17

1.15      bertrand    1: *> \brief \b IZMAX1 finds the index of the first vector element of maximum absolute value.
1.9       bertrand    2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
1.17    ! bertrand    5: * Online html documentation available at
        !             6: *            http://www.netlib.org/lapack/explore-html/
1.9       bertrand    7: *
                      8: *> \htmlonly
1.17    ! bertrand    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">
1.9       bertrand   15: *> [TXT]</a>
1.17    ! bertrand   16: *> \endhtmlonly
1.9       bertrand   17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
1.15      bertrand   21: *       INTEGER          FUNCTION IZMAX1( N, ZX, INCX )
1.17    ! bertrand   22: *
1.9       bertrand   23: *       .. Scalar Arguments ..
                     24: *       INTEGER            INCX, N
                     25: *       ..
                     26: *       .. Array Arguments ..
1.15      bertrand   27: *       COMPLEX*16         ZX( * )
1.9       bertrand   28: *       ..
1.17    ! bertrand   29: *
1.9       bertrand   30: *
                     31: *> \par Purpose:
                     32: *  =============
                     33: *>
                     34: *> \verbatim
                     35: *>
1.15      bertrand   36: *> IZMAX1 finds the index of the first vector element of maximum absolute value.
1.9       bertrand   37: *>
                     38: *> Based on IZAMAX from Level 1 BLAS.
                     39: *> The change is to use the 'genuine' absolute value.
                     40: *> \endverbatim
                     41: *
                     42: *  Arguments:
                     43: *  ==========
                     44: *
                     45: *> \param[in] N
                     46: *> \verbatim
                     47: *>          N is INTEGER
1.15      bertrand   48: *>          The number of elements in the vector ZX.
1.9       bertrand   49: *> \endverbatim
                     50: *>
1.15      bertrand   51: *> \param[in] ZX
1.9       bertrand   52: *> \verbatim
1.15      bertrand   53: *>          ZX is COMPLEX*16 array, dimension (N)
                     54: *>          The vector ZX. The IZMAX1 function returns the index of its first
                     55: *>          element of maximum absolute value.
1.9       bertrand   56: *> \endverbatim
                     57: *>
                     58: *> \param[in] INCX
                     59: *> \verbatim
                     60: *>          INCX is INTEGER
1.15      bertrand   61: *>          The spacing between successive values of ZX.  INCX >= 1.
1.9       bertrand   62: *> \endverbatim
                     63: *
                     64: *  Authors:
                     65: *  ========
                     66: *
1.17    ! bertrand   67: *> \author Univ. of Tennessee
        !            68: *> \author Univ. of California Berkeley
        !            69: *> \author Univ. of Colorado Denver
        !            70: *> \author NAG Ltd.
1.9       bertrand   71: *
1.15      bertrand   72: *> \date February 2014
1.9       bertrand   73: *
1.15      bertrand   74: *> \ingroup complexOTHERauxiliary
1.9       bertrand   75: *
                     76: *> \par Contributors:
                     77: *  ==================
                     78: *>
                     79: *> Nick Higham for use with ZLACON.
                     80: *
                     81: *  =====================================================================
1.15      bertrand   82:       INTEGER FUNCTION IZMAX1( N, ZX, INCX )
1.1       bertrand   83: *
1.17    ! bertrand   84: *  -- LAPACK auxiliary routine (version 3.7.0) --
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..--
1.15      bertrand   87: *     February 2014
1.1       bertrand   88: *
                     89: *     .. Scalar Arguments ..
                     90:       INTEGER            INCX, N
                     91: *     ..
                     92: *     .. Array Arguments ..
1.15      bertrand   93:       COMPLEX*16         ZX(*)
1.1       bertrand   94: *     ..
                     95: *
1.15      bertrand   96: *  =====================================================================
1.1       bertrand   97: *
                     98: *     .. Local Scalars ..
1.15      bertrand   99:       DOUBLE PRECISION   DMAX
1.1       bertrand  100:       INTEGER            I, IX
                    101: *     ..
                    102: *     .. Intrinsic Functions ..
                    103:       INTRINSIC          ABS
                    104: *     ..
                    105: *     .. Executable Statements ..
                    106: *
                    107:       IZMAX1 = 0
1.15      bertrand  108:       IF (N.LT.1 .OR. INCX.LE.0) RETURN
1.1       bertrand  109:       IZMAX1 = 1
1.15      bertrand  110:       IF (N.EQ.1) RETURN
                    111:       IF (INCX.EQ.1) THEN
                    112: *
                    113: *        code for increment equal to 1
                    114: *
                    115:          DMAX = ABS(ZX(1))
                    116:          DO I = 2,N
                    117:             IF (ABS(ZX(I)).GT.DMAX) THEN
                    118:                IZMAX1 = I
                    119:                DMAX = ABS(ZX(I))
                    120:             END IF
                    121:          END DO
                    122:       ELSE
1.1       bertrand  123: *
1.15      bertrand  124: *        code for increment not equal to 1
1.1       bertrand  125: *
1.15      bertrand  126:          IX = 1
                    127:          DMAX = ABS(ZX(1))
                    128:          IX = IX + INCX
                    129:          DO I = 2,N
                    130:             IF (ABS(ZX(IX)).GT.DMAX) THEN
                    131:                IZMAX1 = I
                    132:                DMAX = ABS(ZX(IX))
                    133:             END IF
                    134:             IX = IX + INCX
                    135:          END DO
                    136:       END IF
1.1       bertrand  137:       RETURN
                    138: *
                    139: *     End of IZMAX1
                    140: *
                    141:       END