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982ec720 | 1 | -module(life_cell). |
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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 | ||
29199e7e | 18 | -record(state, {cell_id :: integer() |
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19 | ,name :: string() |
20 | ,cell_state :: 0 | 1 | |
21 | ,neighbors :: list(atom()) | |
22 | ,live_neighbors :: integer() | |
23 | ,num_neighbors :: integer() | |
24 | ,replies_pending :: integer() | |
0a9b8c17 | 25 | ,gen_id :: integer() |
b699b8a4 | 26 | ,early_msgs :: list() |
d2a0e2f9 SK |
27 | }). |
28 | ||
29 | ||
30 | %% ============================================================================ | |
31 | %% API | |
32 | %% ============================================================================ | |
33 | ||
29199e7e | 34 | start_link({_, Name, _}=Datum) -> |
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35 | ServerName = {local, Name}, |
36 | Args = [Datum], | |
37 | Opts = [], | |
38 | gen_server:start_link(ServerName, ?MODULE, Args, Opts). | |
39 | ||
40 | ||
41 | %% ============================================================================ | |
42 | %% Callbacks | |
43 | %% ============================================================================ | |
44 | ||
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45 | init([{CellID, Name, NeighborNames}]) -> |
46 | State = #state{cell_id = CellID | |
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47 | ,name = Name |
48 | ,cell_state = crypto:rand_uniform(0, 2) | |
49 | ,neighbors = NeighborNames | |
50 | ,num_neighbors = length(NeighborNames) | |
51 | ,live_neighbors = 0 | |
52 | ,replies_pending = 0 | |
b699b8a4 | 53 | ,early_msgs = [] |
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54 | }, |
55 | {ok, State}. | |
56 | ||
57 | ||
58 | terminate(_Reason, State) -> | |
59 | {ok, State}. | |
60 | ||
61 | ||
62 | code_change(_Old, State, _Other) -> | |
63 | {ok, State}. | |
64 | ||
65 | ||
66 | handle_call(_Msg, _From, State) -> | |
67 | {reply, ok, State}. | |
68 | ||
69 | ||
0a9b8c17 | 70 | handle_cast({next_gen, GenID}, |
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71 | #state{name=Name |
72 | ,cell_state=CellState | |
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73 | ,neighbors=Neighbors |
74 | ,num_neighbors=NumNeighbors | |
b699b8a4 | 75 | ,early_msgs=EarlyMsgs |
d2a0e2f9 | 76 | }=State) -> |
29199e7e | 77 | |
263bc3ae | 78 | ok = cast_one2all(Neighbors, {state_broadcast, GenID, CellState}), |
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79 | |
80 | % Put stashed messages back in the mailbox, | |
81 | % now that we're ready to handle them | |
263bc3ae | 82 | ok = cast_all2one(Name, EarlyMsgs), |
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83 | |
84 | NewState = State#state{replies_pending=NumNeighbors | |
85 | ,gen_id=GenID | |
86 | ,early_msgs=[] | |
87 | }, | |
88 | ||
89 | {noreply, NewState}; | |
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90 | |
91 | ||
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92 | %% If we receive 'state_broadcast' before we receive 'next_gen', |
93 | %% stash it until we do. | |
94 | %% | |
95 | %% Took me a while to realize this, but sometimes it is possible. The more | |
96 | %% there're cells, the more likely this is to happen. | |
97 | %% | |
ad4f7e77 | 98 | handle_cast({state_broadcast, ReceivedGenID, _NeighborState}=Msg, |
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99 | #state{gen_id=GenID |
100 | ,early_msgs=EarlyMsgs | |
101 | }=State) when GenID =/= ReceivedGenID -> | |
102 | ||
103 | {noreply, State#state{early_msgs=[Msg|EarlyMsgs]}}; | |
d2a0e2f9 | 104 | |
ad4f7e77 | 105 | |
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106 | %% Now that we can be sure that this request is for the current generation, we |
107 | %% can handle it | |
ad4f7e77 | 108 | handle_cast({state_broadcast, GenID, NeighborState}, |
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109 | #state{cell_id=CellID |
110 | ,gen_id=GenID | |
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111 | ,replies_pending=Pending |
112 | ,cell_state=CellState | |
113 | ,live_neighbors=LiveNeighbors | |
114 | }=State) -> | |
115 | ||
116 | NewPending = Pending - 1, | |
117 | NewLiveNeighbors = LiveNeighbors + NeighborState, | |
118 | ||
119 | NewState = State#state{replies_pending=NewPending | |
120 | ,live_neighbors=NewLiveNeighbors | |
121 | }, | |
122 | ||
123 | case NewPending of | |
124 | 0 -> | |
125 | NewCellState = new_state(CellState, NewLiveNeighbors), | |
29199e7e | 126 | ok = life_time:report_state(CellID, GenID, NewCellState), |
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127 | |
128 | {noreply, NewState#state{live_neighbors=0 | |
129 | ,cell_state=NewCellState | |
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130 | } |
131 | }; | |
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132 | |
133 | _N -> | |
134 | {noreply, NewState} | |
135 | end; | |
136 | ||
ad4f7e77 | 137 | |
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138 | handle_cast(_Msg, State) -> |
139 | {noreply, State}. | |
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140 | |
141 | ||
142 | handle_info(_Msg, State) -> | |
143 | {noreply, State}. | |
144 | ||
145 | ||
146 | %% ============================================================================ | |
147 | %% Internal | |
148 | %% ============================================================================ | |
149 | ||
263bc3ae SK |
150 | % Cast all messages to one destination |
151 | cast_all2one(_, []) -> ok; | |
152 | cast_all2one(Server, [Msg | Msgs]) -> | |
b699b8a4 | 153 | ok = gen_server:cast(Server, Msg), |
263bc3ae | 154 | cast_all2one(Server, Msgs). |
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155 | |
156 | ||
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157 | % Cast one message to all destinations |
158 | cast_one2all([], _) -> ok; | |
159 | cast_one2all([Server | Servers], Msg) -> | |
172421cb | 160 | ok = gen_server:cast(Server, Msg), |
263bc3ae | 161 | cast_one2all(Servers, Msg). |
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162 | |
163 | ||
164 | new_state(1, LiveNeighbors) when LiveNeighbors < 2 -> 0; | |
165 | new_state(1, LiveNeighbors) when LiveNeighbors < 4 -> 1; | |
166 | new_state(1, LiveNeighbors) when LiveNeighbors > 3 -> 0; | |
167 | new_state(0, LiveNeighbors) when LiveNeighbors =:= 3 -> 1; | |
168 | new_state(State, _LiveNeighbors) -> State. |