DOUBLE PRECISION FUNCTION DASUM(N,DX,INCX)
C***BEGIN PROLOGUE  DASUM
C***DATE WRITTEN   791001   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  D1A3A
C***KEYWORDS  ADD,BLAS,DOUBLE PRECISION,LINEAR ALGEBRA,MAGNITUDE,SUM,
C             VECTOR
C***AUTHOR  LAWSON, C. L., (JPL)
C           HANSON, R. J., (SNLA)
C           KINCAID, D. R., (U. OF TEXAS)
C           KROGH, F. T., (JPL)
C***PURPOSE  Sum of magnitudes of d.p. vector components
C***DESCRIPTION
C
C                B L A S  Subprogram
C    Description of Parameters
C
C     --Input--
C        N  number of elements in input vector(s)
C       DX  double precision vector with N elements
C     INCX  storage spacing between elements of DX
C
C     --Output--
C    DASUM  double precision result (zero if N .LE. 0)
C
C     Returns sum of magnitudes of double precision DX.
C     DASUM = sum from 0 to N-1 of DABS(DX(1+I*INCX))
C***REFERENCES  LAWSON C.L., HANSON R.J., KINCAID D.R., KROGH F.T.,
C                 *BASIC LINEAR ALGEBRA SUBPROGRAMS FOR FORTRAN USAGE*,
C                 ALGORITHM NO. 539, TRANSACTIONS ON MATHEMATICAL
C                 SOFTWARE, VOLUME 5, NUMBER 3, SEPTEMBER 1979, 308-323
C***ROUTINES CALLED  (NONE)
C***END PROLOGUE  DASUM