anchor.diff:        return x + y
     }
   
  -  let run () =
  +  let run n =
       printf "SerJob: "
       let timer = Stopwatch.StartNew ()
       let r = run (fib n)
  
positive.code:       fib (n-2L) <*> fib (n-1L) |>> fun (x, y) ->
        x + y
  
    let run () =
      printf "ParOpt: "
      let timer = Stopwatch.StartNew ()
      let r = run (fib n)
  
negative.code:     if n < 2L then
        return n
      else
        let! x = Async.StartChild (fib (n-2L))
        let! y = fib (n-1L)
        let! x = x
        return x + y
    }
  
    let run n =
      printf "ParAsc: "
      let timer = Stopwatch.StartNew ()
      let r = Async.RunSynchronously (fib n)
  