anchor.diff:      let cells = Array.zeroCreate nCells
       let before = GC.GetTotalMemory true
       for i=0 to nCells-1 do
  -      cells.[i] <- create i
  +      cells.[i] <- cell i
       printf "%4d b/c " (max 0L (GC.GetTotalMemory true - before) / int64 nCells)
       seq {1 .. nJobs}
       |> Seq.map (fun _ -> async {
  
positive.code:     let before = GC.GetTotalMemory true
      run <| job {
        do! Job.forUpTo 0 (nCells-1) <| fun i ->
              create i |>> fun cell -> cells.[i] <- cell
        do printf "%4d b/c " (max 0L (GC.GetTotalMemory true - before) / int64 nCells)
        return!
          seq {1 .. nJobs}
  
negative.code: 
    let get (c: Cell<'a>) : Job<'a> = Ch.give c.reqCh Get >>. Ch.take c.replyCh
  
    let cell (x: 'a) : Job<Cell<'a>> = Job.delay <| fun () ->
      let c = {reqCh = Ch.Now.create (); replyCh = Ch.Now.create ()}
      Job.start
       (Job.iterate x (fun x ->
         Ch.take c.reqCh >>= function
          | Get   -> Ch.give c.replyCh x >>% x
          | Put x -> Job.result x)) >>% c
  
    let run nCells nJobs nUpdates =
      printf "HopacReq: "
  