001/src/cell.erl

   1 -module(cell).
   2 -behaviour(gen_server).
   3
   4
   5 %% API
   6 -export([start_link/1]).
   7
   8 %% Callbacks
   9 -export([init/1
  10         ,handle_call/3
  11         ,handle_cast/2
  12         ,handle_info/2
  13         ,terminate/2
  14         ,code_change/3
  15         ]).
  16
  17
  18 -record(state, {id              :: integer()
  19                ,name            :: string()
  20                ,cell_state      :: 0 | 1
  21                ,neighbors       :: list(atom())
  22                ,live_neighbors  :: integer()
  23                ,num_neighbors   :: integer()
  24                ,replies_pending :: integer()
  25                }).
  26
  27
  28 %% ============================================================================
  29 %% API
  30 %% ============================================================================
  31
  32 start_link({_ID, Name, _NeighborNames}=Datum) ->
  33     ServerName = {local, Name},
  34     Args = [Datum],
  35     Opts = [],
  36     gen_server:start_link(ServerName, ?MODULE, Args, Opts).
  37
  38
  39 %% ============================================================================
  40 %% Callbacks
  41 %% ============================================================================
  42
  43 init([{ID, Name, NeighborNames}]) ->
  44     State = #state{id=ID
  45                   ,name=Name
  46                   ,cell_state=crypto:rand_uniform(0, 2)
  47                   ,neighbors=NeighborNames
  48                   ,num_neighbors=length(NeighborNames)
  49                   ,live_neighbors=0
  50                   ,replies_pending=0
  51                   },
  52     {ok, State}.
  53
  54
  55 terminate(_Reason, State) ->
  56     {ok, State}.
  57
  58
  59 code_change(_Old, State, _Other) ->
  60     {ok, State}.
  61
  62
  63 handle_call(_Msg, _From, State) ->
  64     {reply, ok, State}.
  65
  66
  67 handle_cast(_Msg, State) ->
  68     {noreply, State}.
  69
  70
  71 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  72
  73 handle_info(tick,
  74     #state{name=Name
  75           ,neighbors=Neighbors
  76           ,num_neighbors=NumNeighbors
  77           }=State) ->
  78
  79     ok = send_all(Neighbors, {request_state, Name}),
  80     {noreply, State#state{replies_pending=NumNeighbors}};
  81
  82
  83 handle_info({request_state, Requester}, State) ->
  84     Requester ! {response_state, State#state.cell_state},
  85     {noreply, State};
  86
  87
  88 handle_info({response_state, NeighborState},
  89     #state{id=ID
  90           ,replies_pending=Pending
  91           ,cell_state=CellState
  92           ,live_neighbors=LiveNeighbors
  93           }=State) ->
  94
  95     NewPending = Pending - 1,
  96     NewLiveNeighbors = LiveNeighbors + NeighborState,
  97
  98     NewState = State#state{replies_pending=NewPending
  99                           ,live_neighbors=NewLiveNeighbors
 100                           },
 101
 102     case NewPending of
 103         0 ->
 104             NewCellState = new_state(CellState, NewLiveNeighbors),
 105             ok = time:cast({tock, {ID, NewCellState}}),
 106
 107             {noreply, NewState#state{live_neighbors=0
 108                                     ,cell_state=NewCellState
 109                                     }};
 110
 111         _N ->
 112             {noreply, NewState}
 113     end;
 114
 115 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 116
 117
 118 handle_info(_Msg, State) ->
 119     {noreply, State}.
 120
 121
 122 %% ============================================================================
 123 %% Internal
 124 %% ============================================================================
 125
 126 send_all([], _) -> ok;
 127 send_all([PID | PIDs], Msg) ->
 128     PID ! Msg,
 129     send_all(PIDs, Msg).
 130
 131
 132 new_state(1, LiveNeighbors) when LiveNeighbors  <  2 -> 0;
 133 new_state(1, LiveNeighbors) when LiveNeighbors  <  4 -> 1;
 134 new_state(1, LiveNeighbors) when LiveNeighbors  >  3 -> 0;
 135 new_state(0, LiveNeighbors) when LiveNeighbors =:= 3 -> 1;
 136 new_state(State, _LiveNeighbors) -> State.