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December 15, 2015 00:49
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-module(coin). | |
-export([start/1, stop/0, coin/2, gather/2, gatherStatus/2]). | |
start(N) -> | |
Gatherpid = spawn(?MODULE, gather, [0, now()]), | |
register(gather, Gatherpid), | |
spawn(?MODULE, gatherStatus, [Gatherpid, 0]), | |
coin(N, Gatherpid). | |
stop() -> | |
whereis(gather) ! {quit}. | |
gatherStatus(Pid, Prevx) -> | |
timer:send_after(300, Pid, {status, Prevx}). | |
gather(X, Start) -> | |
receive | |
{status, Prevx} -> | |
if Prevx==X -> | |
End = now(), | |
io:format("Reached solution: ~w in ~w~n", [X, timer:now_diff(End, Start)/1000000]), | |
spawn(?MODULE, stop, []), | |
gather(X, Start); | |
true-> | |
spawn(?MODULE, gatherStatus, [self(), X]), | |
gather(X, Start) | |
end; | |
{result, N} -> | |
gather(X+N, Start); | |
{quit} -> | |
io:format("Stopping.~n"), | |
ok | |
end. | |
coin(0, Pid) -> | |
Pid ! {result, 1}; | |
coin(N, Pid) -> | |
coin(trunc(N/2), Pid), | |
coin(trunc(N/3), Pid), | |
coin(trunc(N/4), Pid). |
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-module(coin2). | |
-export([coin/2]). | |
coin(0) -> | |
1; | |
coin(N) -> | |
coin(trunc(N/2))+ | |
coin(trunc(N/3))+ | |
coin(trunc(N/4)). | |
coin(N, _) -> | |
Start=now(), | |
Res=coin(N), | |
End=now(), | |
[Res, timer:now_diff(End, Start)/1000000]. |
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-module(coin3). | |
-export([start/1, stop/0, coincal/1, gather/0]). | |
start(N) -> | |
Gatherpid = spawn(?MODULE, gather, []), | |
register(gather, Gatherpid). | |
stop() -> | |
whereis(gather) ! {quit}. | |
gather() -> | |
receive | |
{result, N, Start, End} -> | |
io:format("Reached solution: ~w in ~w~n", [N, timer:now_diff(End, Start)/1000000]), | |
gather(); | |
{quit} -> | |
io:format("Stopping.~n"), | |
ok | |
end. | |
coin(0) -> | |
1; | |
coin(N) -> | |
coin(trunc(N/2))+ | |
coin(trunc(N/3))+ | |
coin(trunc(N/4)). | |
coincal(N) -> | |
Start = now(), | |
Res = coin(N), | |
End = now(), | |
whereis(gather) ! { result, Res, Start, End }. |
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What if you just spawned on the first call, giving you three threads of execution calculating, and only a little bit of startup and messaging overhead?