subroutine comp2 (fn, dfn, xstart, xend, xincr, ystart, yend,
       1  yincr, fname)
  c august 1979 edition. w. fullerton, c3, los alamos scientific lab.
        double precision dfn, xstart, xend, xincr, ystart, yend, yincr,
       1  dx, dy, df
        integer fname(1), fmt(23)
        external fn, dfn, i1mach
  c
        call s9comp (39, fmt, nwd)
        iwunit = i1mach(2)
        write (iwunit, 5)
   5    format (1h1)
        write (iwunit, fmt) (fname(i), i=1,nwd), (fname(i), i=1,nwd)
        write (iwunit, 10)
   10   format (1h+, 8x, 1hx, 12x, 1hy, 78x, 4haerr, 8x, 4hrerr)
  c
        aerrmx = 0.0
        rerrmx = 0.0
        do 40 i=1,21
          dx = xstart + dble(float(i-1))*xincr
          if (dx.gt.xend) go to 50
  c
          write (iwunit, 20)
          do 30 j=1,21
            dy = ystart + dble(float(j-1))*yincr
            if (dy.gt.yend) go to 40
  c
            x = dx
            y = dy
            f = fn (x, y)
            df = dfn (dble(x), dble(y))
            aerr = df - dble(f)
            rerr = 0.0
            if (df.ne.0.0d0) rerr = abs (aerr/sngl(df))
  c
            aerrmx = amax1 (abs(aerr), aerrmx)
            rerrmx = amax1 (rerr, rerrmx)
            df = dfn (dx, dy)
  c
            write (iwunit, 20) x, y, f, df, aerr, rerr
   20       format (1x, 2e13.5, e25.15, d40.30, 3x, 2e12.3)
   30     continue
   40   continue
  c
   50   write (iwunit, 60) aerrmx, rerrmx
   60   format (/95x, 2e12.3)
  c
        return
        end