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    1: *> \brief \b IZMAX1 finds the index of the first vector element of maximum absolute value.
    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, ZX, INCX )
   22: *
   23: *       .. Scalar Arguments ..
   24: *       INTEGER            INCX, N
   25: *       ..
   26: *       .. Array Arguments ..
   27: *       COMPLEX*16         ZX( * )
   28: *       ..
   29: *
   30: *
   31: *> \par Purpose:
   32: *  =============
   33: *>
   34: *> \verbatim
   35: *>
   36: *> IZMAX1 finds the index of the first vector element of maximum absolute value.
   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
   48: *>          The number of elements in the vector ZX.
   49: *> \endverbatim
   50: *>
   51: *> \param[in] ZX
   52: *> \verbatim
   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.
   56: *> \endverbatim
   57: *>
   58: *> \param[in] INCX
   59: *> \verbatim
   60: *>          INCX is INTEGER
   61: *>          The spacing between successive values of ZX.  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: *
   72: *> \ingroup complexOTHERauxiliary
   73: *
   74: *> \par Contributors:
   75: *  ==================
   76: *>
   77: *> Nick Higham for use with ZLACON.
   78: *
   79: *  =====================================================================
   80:       INTEGER FUNCTION IZMAX1( N, ZX, INCX )
   81: *
   82: *  -- LAPACK auxiliary routine --
   83: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
   84: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   85: *
   86: *     .. Scalar Arguments ..
   87:       INTEGER            INCX, N
   88: *     ..
   89: *     .. Array Arguments ..
   90:       COMPLEX*16         ZX(*)
   91: *     ..
   92: *
   93: *  =====================================================================
   94: *
   95: *     .. Local Scalars ..
   96:       DOUBLE PRECISION   DMAX
   97:       INTEGER            I, IX
   98: *     ..
   99: *     .. Intrinsic Functions ..
  100:       INTRINSIC          ABS
  101: *     ..
  102: *     .. Executable Statements ..
  103: *
  104:       IZMAX1 = 0
  105:       IF (N.LT.1 .OR. INCX.LE.0) RETURN
  106:       IZMAX1 = 1
  107:       IF (N.EQ.1) RETURN
  108:       IF (INCX.EQ.1) THEN
  109: *
  110: *        code for increment equal to 1
  111: *
  112:          DMAX = ABS(ZX(1))
  113:          DO I = 2,N
  114:             IF (ABS(ZX(I)).GT.DMAX) THEN
  115:                IZMAX1 = I
  116:                DMAX = ABS(ZX(I))
  117:             END IF
  118:          END DO
  119:       ELSE
  120: *
  121: *        code for increment not equal to 1
  122: *
  123:          IX = 1
  124:          DMAX = ABS(ZX(1))
  125:          IX = IX + INCX
  126:          DO I = 2,N
  127:             IF (ABS(ZX(IX)).GT.DMAX) THEN
  128:                IZMAX1 = I
  129:                DMAX = ABS(ZX(IX))
  130:             END IF
  131:             IX = IX + INCX
  132:          END DO
  133:       END IF
  134:       RETURN
  135: *
  136: *     End of IZMAX1
  137: *
  138:       END