subroutine  dscal(n,da,dx,incx) 8
!
!     scales a vector by a constant.
!     uses unrolled loops for increment equal to one.
!     jack dongarra, linpack, 3/11/78.
!     modified 3/93 to return if incx .le. 0.
!     modified 12/3/93, array(1) declarations changed to array(*)
!
      double precision da,dx(*)
      integer i,incx,m,mp1,n,nincx
!
      if( n.le.0 .or. incx.le.0 )return
      if(incx.eq.1)go to 20
!
!        code for increment not equal to 1
!
      nincx = n*incx
      do 10 i = 1,nincx,incx
        dx(i) = da*dx(i)
   10 continue
      return
!
!        code for increment equal to 1
!
!
!        clean-up loop
!
   20 m = mod(n,5)
      if( m .eq. 0 ) go to 40
      do 30 i = 1,m
        dx(i) = da*dx(i)
   30 continue
      if( n .lt. 5 ) return
   40 mp1 = m + 1
      do 50 i = mp1,n,5
        dx(i) = da*dx(i)
        dx(i + 1) = da*dx(i + 1)
        dx(i + 2) = da*dx(i + 2)
        dx(i + 3) = da*dx(i + 3)
        dx(i + 4) = da*dx(i + 4)
   50 continue
      return
      end subroutine  dscal