c @(#)Copyright (c), 1987, 1993 StatSci, Inc.  All rights reserved.
        subroutine arsim(x, n, phi)
        integer n, i
        real*8 x(n), phi
        do 10 i = 2, n
                x(i) = phi * x(i-1) + x(i)
10      continue
        return
        end