Szymański's algorithm: Difference between revisions
Add C# implementation
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https://en.wikipedia.org/wiki/Szyma%C5%84ski%27s_algorithm
"""
=={{header|C#}}==
{{trans|Julia}}
<syntaxhighlight lang="C#">
using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Threading;
class Program
{
private static ConcurrentDictionary<int, int> dict = new ConcurrentDictionary<int, int>();
private static int criticalValue = 1;
private static readonly object lockObject = new object();
static void Main(string[] args)
{
TestSzymanski(20);
}
static int Flag(int id)
{
return dict.GetOrAdd(id, 0);
}
static void RunSzymanski(int id, int[] allszy)
{
var others = allszy.Where(t => t != id).ToArray();
dict[id] = 1; // Standing outside waiting room
while (others.Any(t => Flag(t) >= 3))
{
Thread.Yield();
}
dict[id] = 3; // Standing in doorway
if (others.Any(t => Flag(t) == 1))
{
dict[id] = 2; // Waiting for other processes to enter
while (!others.Any(t => Flag(t) == 4))
{
Thread.Yield();
}
}
dict[id] = 4; // The door is closed
foreach (var t in others)
{
if (t >= id) continue;
while (Flag(t) > 1)
{
Thread.Yield();
}
}
// critical section
lock (lockObject)
{
criticalValue += id * 3;
criticalValue /= 2;
Console.WriteLine($"Thread {id} changed the critical value to {criticalValue}.");
}
// end critical section
// Exit protocol
foreach (var t in others)
{
if (t <= id) continue;
while (!new[] { 0, 1, 4 }.Contains(Flag(t)))
{
Thread.Yield();
}
}
dict[id] = 0; // Leave. Reopen door if nobody is still in the waiting room
}
static void TestSzymanski(int N)
{
int[] allszy = Enumerable.Range(1, N).ToArray();
var threads = allszy.Select(i => new Thread(() => RunSzymanski(i, allszy))).ToArray();
foreach (var thread in threads)
{
thread.Start();
}
foreach (var thread in threads)
{
thread.Join();
}
}
}
</syntaxhighlight>
{{out}}
<pre>
Thread 1 changed the critical value to 2.
Thread 2 changed the critical value to 4.
Thread 3 changed the critical value to 6.
Thread 4 changed the critical value to 9.
Thread 5 changed the critical value to 12.
Thread 6 changed the critical value to 15.
Thread 7 changed the critical value to 18.
Thread 8 changed the critical value to 21.
Thread 9 changed the critical value to 24.
Thread 10 changed the critical value to 27.
Thread 11 changed the critical value to 30.
Thread 12 changed the critical value to 33.
Thread 13 changed the critical value to 36.
Thread 14 changed the critical value to 39.
Thread 15 changed the critical value to 42.
Thread 16 changed the critical value to 45.
Thread 17 changed the critical value to 48.
Thread 18 changed the critical value to 51.
Thread 19 changed the critical value to 54.
Thread 20 changed the critical value to 57.
</pre>
=={{header|FreeBASIC}}==
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