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    , tryBalance

-- | Run a balance move

tryBalance :: Table       -- ^ The starting table

           -> Int         -- ^ Remaining length

           -> Bool        -- ^ Allow disk moves

           -> Score       -- ^ Score at which to stop

           -> Maybe Table -- ^ The resulting table and commands

tryBalance ini_tbl max_rounds disk_moves min_score =

    let Table ini_nl ini_il ini_cv ini_plc = ini_tbl

        ini_plc_len = length ini_plc

        allowed_next = (max_rounds < 0 || ini_plc_len < max_rounds) &&

                       ini_cv > min_score

    in

      if allowed_next

      then let all_inst = Container.elems ini_il

               node_idx = map Node.idx . filter (not . Node.offline) $

                          Container.elems ini_nl

               fin_tbl = checkMove node_idx disk_moves ini_tbl all_inst

               (Table _ _ fin_cv _) = fin_tbl

           in

             if fin_cv < ini_cv

             then Just fin_tbl -- this round made success, try deeper

             else Nothing

      else Nothing

    let Cluster.Table ini_nl ini_il _ _ = ini_tbl

        m_fin_tbl = Cluster.tryBalance ini_tbl max_rounds disk_moves min_score

      case m_fin_tbl of

        Just fin_tbl ->

            do

              let

                  (Cluster.Table _ _ _ fin_plc) = fin_tbl

                  fin_plc_len = length fin_plc

                  (sol_line, cmds) = Cluster.printSolutionLine ini_nl ini_il

                                     nmlen imlen (head fin_plc) fin_plc_len

                  upd_cmd_strs = cmds:cmd_strs

              unless oneline $ do

                       putStrLn sol_line

                       hFlush stdout

              iterateDepth fin_tbl max_rounds disk_moves

                           nmlen imlen upd_cmd_strs oneline min_score

        Nothing -> return (ini_tbl, cmd_strs)