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    1: *> \brief \b IDAMAX
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at 
    6: *            http://www.netlib.org/lapack/explore-html/ 
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *       INTEGER FUNCTION IDAMAX(N,DX,INCX)
   12: * 
   13: *       .. Scalar Arguments ..
   14: *       INTEGER INCX,N
   15: *       ..
   16: *       .. Array Arguments ..
   17: *       DOUBLE PRECISION DX(*)
   18: *       ..
   19: *  
   20: *
   21: *> \par Purpose:
   22: *  =============
   23: *>
   24: *> \verbatim
   25: *>
   26: *>    IDAMAX finds the index of element having max. absolute value.
   27: *> \endverbatim
   28: *
   29: *  Authors:
   30: *  ========
   31: *
   32: *> \author Univ. of Tennessee 
   33: *> \author Univ. of California Berkeley 
   34: *> \author Univ. of Colorado Denver 
   35: *> \author NAG Ltd. 
   36: *
   37: *> \date November 2011
   38: *
   39: *> \ingroup aux_blas
   40: *
   41: *> \par Further Details:
   42: *  =====================
   43: *>
   44: *> \verbatim
   45: *>
   46: *>     jack dongarra, linpack, 3/11/78.
   47: *>     modified 3/93 to return if incx .le. 0.
   48: *>     modified 12/3/93, array(1) declarations changed to array(*)
   49: *> \endverbatim
   50: *>
   51: *  =====================================================================
   52:       INTEGER FUNCTION IDAMAX(N,DX,INCX)
   53: *
   54: *  -- Reference BLAS level1 routine (version 3.4.0) --
   55: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
   56: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   57: *     November 2011
   58: *
   59: *     .. Scalar Arguments ..
   60:       INTEGER INCX,N
   61: *     ..
   62: *     .. Array Arguments ..
   63:       DOUBLE PRECISION DX(*)
   64: *     ..
   65: *
   66: *  =====================================================================
   67: *
   68: *     .. Local Scalars ..
   69:       DOUBLE PRECISION DMAX
   70:       INTEGER I,IX
   71: *     ..
   72: *     .. Intrinsic Functions ..
   73:       INTRINSIC DABS
   74: *     ..
   75:       IDAMAX = 0
   76:       IF (N.LT.1 .OR. INCX.LE.0) RETURN
   77:       IDAMAX = 1
   78:       IF (N.EQ.1) RETURN
   79:       IF (INCX.EQ.1) THEN
   80: *
   81: *        code for increment equal to 1
   82: *
   83:          DMAX = DABS(DX(1))
   84:          DO I = 2,N
   85:             IF (DABS(DX(I)).GT.DMAX) THEN
   86:                IDAMAX = I
   87:                DMAX = DABS(DX(I))
   88:             END IF
   89:          END DO
   90:       ELSE
   91: *
   92: *        code for increment not equal to 1
   93: *
   94:          IX = 1
   95:          DMAX = DABS(DX(1))
   96:          IX = IX + INCX
   97:          DO I = 2,N
   98:             IF (DABS(DX(IX)).GT.DMAX) THEN
   99:                IDAMAX = I
  100:                DMAX = DABS(DX(IX))
  101:             END IF
  102:             IX = IX + INCX
  103:          END DO
  104:       END IF
  105:       RETURN
  106:       END