Mutex: Difference between revisions
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<code>when</code> blocks and <code>Ref.whenResolved</code> return a ''promise'' for the result of the deferred action, so the mutex here waits for the gratuitously complicated increment to complete before becoming available for the next action. |
<code>when</code> blocks and <code>Ref.whenResolved</code> return a ''promise'' for the result of the deferred action, so the mutex here waits for the gratuitously complicated increment to complete before becoming available for the next action. |
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=={{header|Erlang}}== |
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Erlang has no mutexes so this is a super simple one, hand built to allow 3 slowly printing processes to print until done before the next one starts. |
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<lang Erlang> |
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-module( mutex ). |
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-export( [task/0] ). |
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task() -> |
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Mutex = erlang:spawn( fun() -> loop() end ), |
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[erlang:spawn(fun() -> random:seed( X, 0, 0 ), print(Mutex, X, 3) end) || X <- lists:seq(1, 3)]. |
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loop() -> |
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receive |
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{acquire, Pid} -> |
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Pid ! {access, erlang:self()}, |
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receive |
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{release, Pid} -> loop() |
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end |
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end. |
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mutex_acquire( Pid ) -> |
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Pid ! {acquire, erlang:self()}, |
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receive |
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{access, Pid} -> ok |
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end. |
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mutex_release( Pid ) -> Pid ! {release, erlang:self()}. |
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print( _Mutex, _N, 0 ) -> ok; |
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print( Mutex, N, M ) -> |
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timer:sleep( random:uniform(100) ), |
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mutex_acquire( Mutex ), |
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io:fwrite( "Print ~p: ", [N] ), |
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[print_slow(X) || X <- lists:seq(1, 3)], |
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io:nl(), |
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mutex_release( Mutex ), |
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print( Mutex, N, M - 1 ). |
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print_slow( X ) -> |
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io:fwrite( " ~p", [X] ), |
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timer:sleep( 100 ). |
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</lang> |
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{{out}} |
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<pre> |
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27> mutex:task(). |
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Print 2: 1 2 3 |
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Print 1: 1 2 3 |
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Print 3: 1 2 3 |
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Print 2: 1 2 3 |
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Print 1: 1 2 3 |
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Print 3: 1 2 3 |
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Print 2: 1 2 3 |
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Print 1: 1 2 3 |
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Print 3: 1 2 3 |
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</pre> |
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=={{header|Go}}== |
=={{header|Go}}== |
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