How to resolve the algorithm Metered concurrency step by step in the Erlang programming language

Published on 12 May 2024 09:40 PM
#Erlang

How to resolve the algorithm Metered concurrency step by step in the Erlang programming language

Table of Contents

Problem Statement

The goal of this task is to create a counting semaphore used to control the execution of a set of concurrent units. This task intends to demonstrate coordination of active concurrent units through the use of a passive concurrent unit. The operations for a counting semaphore are acquire, release, and count. Each active concurrent unit should attempt to acquire the counting semaphore before executing its assigned duties. In this case the active concurrent unit should report that it has acquired the semaphore. It should sleep for 2 seconds and then release the semaphore.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Metered concurrency step by step in the Erlang programming language

Source code in the erlang programming language

-module(metered).
-compile(export_all).

create_semaphore(N) ->
    spawn(?MODULE, sem_loop, [N,N]).

sem_loop(0,Max) ->
    io:format("Resources exhausted~n"),
    receive
        {release, PID} ->
            PID ! released,
            sem_loop(1,Max);
        {stop, _PID} ->
            ok
    end;
sem_loop(N,N) ->
    receive
        {acquire, PID} ->
            PID ! acquired,
            sem_loop(N-1,N);
        {stop, _PID} ->
            ok
    end;
sem_loop(N,Max) ->
    receive
        {release, PID} ->
            PID ! released,
            sem_loop(N+1,Max);
        {acquire, PID} ->
            PID ! acquired,
            sem_loop(N-1,Max);
        {stop, _PID} ->
            ok
    end.

release(Sem) ->
    Sem ! {release, self()},
    receive
        released ->
            ok
    end.
acquire(Sem) ->
    Sem ! {acquire, self()},
    receive
        acquired ->
            ok
    end.

start() -> create_semaphore(10).

stop(Sem) -> Sem ! {stop, self()}.

worker(P,N,Sem) ->
    acquire(Sem),
    io:format("Worker ~b has the acquired semaphore~n",[N]),
    timer:sleep(500 * random:uniform(4)),
    release(Sem),
    io:format("Worker ~b has released the semaphore~n",[N]),
    P ! {done, self()}.

test() ->
    Sem = start(),
    Pids = lists:map(fun (N) ->
                             spawn(?MODULE, worker, [self(),N,Sem])
                     end, lists:seq(1,20)),
    lists:foreach(fun (P) -> receive {done, P} -> ok end end, Pids),
    stop(Sem).

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