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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: *  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 double_blas_level1
   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:       DOUBLE PRECISION FUNCTION DASUM(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 DTEMP
   70:       INTEGER I,M,MP1,NINCX
   71: *     ..
   72: *     .. Intrinsic Functions ..
   73:       INTRINSIC DABS,MOD
   74: *     ..
   75:       DASUM = 0.0d0
   76:       DTEMP = 0.0d0
   77:       IF (N.LE.0 .OR. INCX.LE.0) RETURN
   78:       IF (INCX.EQ.1) THEN
   79: *        code for increment equal to 1
   80: *
   81: *
   82: *        clean-up loop
   83: *
   84:          M = MOD(N,6)
   85:          IF (M.NE.0) THEN
   86:             DO I = 1,M
   87:                DTEMP = DTEMP + DABS(DX(I))
   88:             END DO
   89:             IF (N.LT.6) THEN
   90:                DASUM = DTEMP
   91:                RETURN
   92:             END IF
   93:          END IF
   94:          MP1 = M + 1
   95:          DO I = MP1,N,6
   96:             DTEMP = DTEMP + DABS(DX(I)) + DABS(DX(I+1)) +
   97:      $              DABS(DX(I+2)) + DABS(DX(I+3)) +
   98:      $              DABS(DX(I+4)) + DABS(DX(I+5))
   99:          END DO
  100:       ELSE
  101: *
  102: *        code for increment not equal to 1
  103: *
  104:          NINCX = N*INCX
  105:          DO I = 1,NINCX,INCX
  106:             DTEMP = DTEMP + DABS(DX(I))
  107:          END DO
  108:       END IF
  109:       DASUM = DTEMP
  110:       RETURN
  111:       END