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    1: *> \brief \b DASUM
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at
    6: *            http://www.netlib.org/lapack/explore-html/
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *       DOUBLE PRECISION FUNCTION DASUM(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: *>    DASUM takes the sum of the absolute values.
   27: *> \endverbatim
   28: *
   29: *  Arguments:
   30: *  ==========
   31: *
   32: *> \param[in] N
   33: *> \verbatim
   34: *>          N is INTEGER
   35: *>         number of elements in input vector(s)
   36: *> \endverbatim
   37: *>
   38: *> \param[in] DX
   39: *> \verbatim
   40: *>          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
   41: *> \endverbatim
   42: *>
   43: *> \param[in] INCX
   44: *> \verbatim
   45: *>          INCX is INTEGER
   46: *>         storage spacing between elements of DX
   47: *> \endverbatim
   48: *
   49: *  Authors:
   50: *  ========
   51: *
   52: *> \author Univ. of Tennessee
   53: *> \author Univ. of California Berkeley
   54: *> \author Univ. of Colorado Denver
   55: *> \author NAG Ltd.
   56: *
   57: *> \date November 2017
   58: *
   59: *> \ingroup double_blas_level1
   60: *
   61: *> \par Further Details:
   62: *  =====================
   63: *>
   64: *> \verbatim
   65: *>
   66: *>     jack dongarra, linpack, 3/11/78.
   67: *>     modified 3/93 to return if incx .le. 0.
   68: *>     modified 12/3/93, array(1) declarations changed to array(*)
   69: *> \endverbatim
   70: *>
   71: *  =====================================================================
   72:       DOUBLE PRECISION FUNCTION DASUM(N,DX,INCX)
   73: *
   74: *  -- Reference BLAS level1 routine (version 3.8.0) --
   75: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
   76: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   77: *     November 2017
   78: *
   79: *     .. Scalar Arguments ..
   80:       INTEGER INCX,N
   81: *     ..
   82: *     .. Array Arguments ..
   83:       DOUBLE PRECISION DX(*)
   84: *     ..
   85: *
   86: *  =====================================================================
   87: *
   88: *     .. Local Scalars ..
   89:       DOUBLE PRECISION DTEMP
   90:       INTEGER I,M,MP1,NINCX
   91: *     ..
   92: *     .. Intrinsic Functions ..
   93:       INTRINSIC DABS,MOD
   94: *     ..
   95:       DASUM = 0.0d0
   96:       DTEMP = 0.0d0
   97:       IF (N.LE.0 .OR. INCX.LE.0) RETURN
   98:       IF (INCX.EQ.1) THEN
   99: *        code for increment equal to 1
  100: *
  101: *
  102: *        clean-up loop
  103: *
  104:          M = MOD(N,6)
  105:          IF (M.NE.0) THEN
  106:             DO I = 1,M
  107:                DTEMP = DTEMP + DABS(DX(I))
  108:             END DO
  109:             IF (N.LT.6) THEN
  110:                DASUM = DTEMP
  111:                RETURN
  112:             END IF
  113:          END IF
  114:          MP1 = M + 1
  115:          DO I = MP1,N,6
  116:             DTEMP = DTEMP + DABS(DX(I)) + DABS(DX(I+1)) +
  117:      $              DABS(DX(I+2)) + DABS(DX(I+3)) +
  118:      $              DABS(DX(I+4)) + DABS(DX(I+5))
  119:          END DO
  120:       ELSE
  121: *
  122: *        code for increment not equal to 1
  123: *
  124:          NINCX = N*INCX
  125:          DO I = 1,NINCX,INCX
  126:             DTEMP = DTEMP + DABS(DX(I))
  127:          END DO
  128:       END IF
  129:       DASUM = DTEMP
  130:       RETURN
  131:       END