X-Git-Url: https://git.xandkar.net/?a=blobdiff_plain;f=001%2Fsrc%2Flife_cell.erl;h=9f7b1717d3fd6eafd0f713bb13ac103a1d052c63;hb=90456d0857c0e6ac3f9550cc18f27ad158fa8dd8;hp=2ffda4b369076d96f90ed20d1e50abbb605f3904;hpb=0a9b8c1755fb6126d79e3c51b84df9ff90fbbf6a;p=cellular-automata.git

diff --git a/001/src/life_cell.erl b/001/src/life_cell.erl
index 2ffda4b..9f7b171 100644
--- a/001/src/life_cell.erl
+++ b/001/src/life_cell.erl
@@ -15,7 +15,7 @@
         ]).
 
 
--record(state, {id              :: integer()
+-record(state, {cell_id         :: integer()
                ,name            :: string()
                ,cell_state      :: 0 | 1
                ,neighbors       :: list(atom())
@@ -23,6 +23,7 @@
                ,num_neighbors   :: integer()
                ,replies_pending :: integer()
                ,gen_id          :: integer()
+               ,early_msgs      :: list()
                }).
 
 
@@ -30,57 +31,81 @@
 %% API
 %% ============================================================================
 
-start_link({_ID, Name, _NeighborNames}=Datum) ->
+start_link({_, Name, _}=Datum) ->
     ServerName = {local, Name},
     Args = [Datum],
     Opts = [],
     gen_server:start_link(ServerName, ?MODULE, Args, Opts).
 
 
+%% ============================================================================
+%% Callbacks (unused)
+%% ============================================================================
+
+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}.
+
+
 %% ============================================================================
 %% Callbacks
 %% ============================================================================
 
-init([{ID, Name, NeighborNames}]) ->
-    State = #state{id              = ID
+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}.
 
 
-terminate(_Reason, State) ->
-    {ok, State}.
-
-
-code_change(_Old, State, _Other) ->
-    {ok, State}.
-
-
-handle_call(_Msg, _From, State) ->
-    {reply, ok, State}.
-
-
 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, gen_id=GenID}};
 
+    ok = cast_one2all(Neighbors, {state_broadcast, GenID, CellState}),
+
+    % Put stashed messages back in the mailbox,
+    % now that we're ready to handle them
+    ok = 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 ->
 
-handle_cast({request_state, Requester}, State) ->
-    ok = gen_server:cast(Requester, {response_state, State#state.cell_state}),
-    {noreply, State};
+    {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
@@ -96,7 +121,7 @@ handle_cast({response_state, NeighborState},
     case NewPending of
         0 ->
             NewCellState = new_state(CellState, NewLiveNeighbors),
-            ok = life_time:report_state(ID, NewCellState),
+            ok = life_time:report_state(CellID, GenID, NewCellState),
 
             {noreply, NewState#state{live_neighbors=0
                                     ,cell_state=NewCellState
@@ -112,18 +137,22 @@ handle_cast(_Msg, State) ->
     {noreply, State}.
 
 
-handle_info(_Msg, State) ->
-    {noreply, State}.
-
-
 %% ============================================================================
 %% Internal
 %% ============================================================================
 
-cast_all([], _) -> ok;
-cast_all([Server | Servers], Msg) ->
+% Cast all messages to one destination
+cast_all2one(_, []) -> ok;
+cast_all2one(Server, [Msg | Msgs]) ->
+    ok = gen_server:cast(Server, Msg),
+    cast_all2one(Server, Msgs).
+
+
+% Cast one message to all destinations
+cast_one2all([], _) -> ok;
+cast_one2all([Server | Servers], Msg) ->
     ok = gen_server:cast(Server, Msg),
-    cast_all(Servers, Msg).
+    cast_one2all(Servers, Msg).
 
 
 new_state(1, LiveNeighbors) when LiveNeighbors  <  2 -> 0;