DOUBLE PRECISION FUNCTION DSUM(N,DX,INCX)
      IMPLICIT DOUBLE PRECISION (A-H,O-Z)
      DIMENSION DX(*)
      IF (N.LE.0D0) DSUM=0D0
      SUM=0D0
      DO 10 I=1,N,INCX
         SUM=SUM+DX(I)
 10      CONTINUE
      DSUM=SUM
      RETURN
      END