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