]).
--record(state, {id :: integer()
+-record(state, {cell_id :: integer()
,name :: string()
,cell_state :: 0 | 1
,neighbors :: list(atom())
,live_neighbors :: integer()
,num_neighbors :: integer()
,replies_pending :: integer()
+ ,gen_id :: integer()
+ ,early_msgs :: list()
}).
%% API
%% ============================================================================
-start_link({_ID, Name, _NeighborNames}=Datum) ->
+start_link({_, Name, _}=Datum) ->
ServerName = {local, Name},
Args = [Datum],
Opts = [],
%% ============================================================================
-%% Callbacks
+%% Callbacks (unused)
%% ============================================================================
-init([{ID, Name, NeighborNames}]) ->
- State = #state{id=ID
- ,name=Name
- ,cell_state=crypto:rand_uniform(0, 2)
- ,neighbors=NeighborNames
- ,num_neighbors=length(NeighborNames)
- ,live_neighbors=0
- ,replies_pending=0
- },
- {ok, State}.
-
+handle_call(_Msg, _From, State) -> {reply, ok, State}.
+handle_info(_Msg, State) -> {noreply, State}.
+code_change(_Old, State, _Other) -> {ok, State}.
+terminate(_Reason, State) -> {ok, State}.
-terminate(_Reason, State) ->
- {ok, State}.
+%% ============================================================================
+%% Callbacks
+%% ============================================================================
-code_change(_Old, State, _Other) ->
+init([{CellID, Name, NeighborNames}]) ->
+ State = #state{cell_id = CellID
+ ,name = Name
+ ,cell_state = crypto:rand_uniform(0, 2)
+ ,neighbors = NeighborNames
+ ,num_neighbors = length(NeighborNames)
+ ,live_neighbors = 0
+ ,replies_pending = 0
+ ,early_msgs = []
+ },
{ok, State}.
-handle_call(_Msg, _From, State) ->
- {reply, ok, State}.
-
-
-handle_cast(tick,
+handle_cast({next_gen, GenID},
#state{name=Name
+ ,cell_state=CellState
,neighbors=Neighbors
,num_neighbors=NumNeighbors
+ ,early_msgs=EarlyMsgs
}=State) ->
- ok = cast_all(Neighbors, {request_state, Name}),
- {noreply, State#state{replies_pending=NumNeighbors}};
+ ok = life_lib:cast_one2all(Neighbors, {state_broadcast, GenID, CellState}),
-handle_cast({request_state, Requester}, State) ->
- ok = gen_server:cast(Requester, {response_state, State#state.cell_state}),
- {noreply, State};
+ % Put stashed messages back in the mailbox,
+ % now that we're ready to handle them
+ ok = life_lib:cast_all2one(Name, EarlyMsgs),
+
+ NewState = State#state{replies_pending=NumNeighbors
+ ,gen_id=GenID
+ ,early_msgs=[]
+ },
+
+ {noreply, NewState};
+
+
+%% If we receive 'state_broadcast' before we receive 'next_gen',
+%% stash it until we do.
+%%
+%% Took me a while to realize this, but sometimes it is possible. The more
+%% there're cells, the more likely this is to happen.
+%%
+handle_cast({state_broadcast, ReceivedGenID, _NeighborState}=Msg,
+ #state{gen_id=GenID
+ ,early_msgs=EarlyMsgs
+ }=State) when GenID =/= ReceivedGenID ->
+
+ {noreply, State#state{early_msgs=[Msg|EarlyMsgs]}};
-handle_cast({response_state, NeighborState},
- #state{id=ID
+%% Now that we can be sure that this request is for the current generation, we
+%% can handle it
+handle_cast({state_broadcast, GenID, NeighborState},
+ #state{cell_id=CellID
+ ,gen_id=GenID
,replies_pending=Pending
,cell_state=CellState
,live_neighbors=LiveNeighbors
case NewPending of
0 ->
NewCellState = new_state(CellState, NewLiveNeighbors),
- ok = life_time:tock(ID, NewCellState),
+ ok = life_time:report_state(CellID, GenID, NewCellState),
{noreply, NewState#state{live_neighbors=0
,cell_state=NewCellState
{noreply, State}.
-handle_info(_Msg, State) ->
- {noreply, State}.
-
-
%% ============================================================================
%% Internal
%% ============================================================================
-cast_all([], _) -> ok;
-cast_all([Server | Servers], Msg) ->
- ok = gen_server:cast(Server, Msg),
- cast_all(Servers, Msg).
-
-
new_state(1, LiveNeighbors) when LiveNeighbors < 2 -> 0;
new_state(1, LiveNeighbors) when LiveNeighbors < 4 -> 1;
new_state(1, LiveNeighbors) when LiveNeighbors > 3 -> 0;