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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: *> \date February 2014
   73: *
   74: *> \ingroup complexOTHERauxiliary
   75: *
   76: *> \par Contributors:
   77: *  ==================
   78: *>
   79: *> Nick Higham for use with ZLACON.
   80: *
   81: *  =====================================================================
   82:       INTEGER FUNCTION IZMAX1( N, ZX, INCX )
   83: *
   84: *  -- LAPACK auxiliary routine (version 3.7.0) --
   85: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
   86: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   87: *     February 2014
   88: *
   89: *     .. Scalar Arguments ..
   90:       INTEGER            INCX, N
   91: *     ..
   92: *     .. Array Arguments ..
   93:       COMPLEX*16         ZX(*)
   94: *     ..
   95: *
   96: *  =====================================================================
   97: *
   98: *     .. Local Scalars ..
   99:       DOUBLE PRECISION   DMAX
  100:       INTEGER            I, IX
  101: *     ..
  102: *     .. Intrinsic Functions ..
  103:       INTRINSIC          ABS
  104: *     ..
  105: *     .. Executable Statements ..
  106: *
  107:       IZMAX1 = 0
  108:       IF (N.LT.1 .OR. INCX.LE.0) RETURN
  109:       IZMAX1 = 1
  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
  123: *
  124: *        code for increment not equal to 1
  125: *
  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
  137:       RETURN
  138: *
  139: *     End of IZMAX1
  140: *
  141:       END