C# 4 and .NET 4

530 ❘ ChaPTer 20 threAds, tAsks, And synchrOnizAtiOn
}
}
Console.WriteLine("Calculation completed from task {0}. {1} " +
"times a, {2} times z", Task.Current.Id, charCount[0],
charCount[25]);
barrier.RemoveParticipant();
Console.WriteLine("Task {0} removed from barrier, " +
"remaining participants {1}", Task.Current.Id,
barrier.ParticipantsRemaining);
return charCount;
With the Main() method, a Barrier instance is created. In the constructor, you can specify the number of
participants. In the sample, this number is 3 because there are two created tasks, and the Main() method
itself is a participant as well. Using a TaskFactory, two tasks are created to fork the iteration through the
collection into two parts. After starting the tasks, using SignalAndWait(), the main method signals its
completion and waits until all remaining participants either signal the completion or remove themselves as
participants from the barrier. As soon as all participants are ready, the results from the tasks are taken and
zipped together with the Zip() extension method.
static void Main()
{
const int numberTasks = 2;
const int partitionSize = 1000000;
var data = new List(FillData(partitionSize * numberTasks));
readerWriterlockslim
}
var barrier = new Barrier(numberTasks + 1);
var taskFactory = new TaskFactory();
var tasks = new Task[numberTasks];
for (int i = 0; i < participants; i++)
{
tasks[i] = taskFactory.StartNew(CalculationInTask,
Tuple.Create(i, partitionSize, barrier, data));
}
barrier.SignalAndWait();
var resultCollection = tasks[0].Result.Zip(tasks[1].Result, (c1, c2) =
{
return c1 + c2;
});
char ch = 'a';
int sum = 0;
foreach (var x in resultCollection)
{
Console.WriteLine("{0}, count: {1}", ch++, x);
sum += x;
}
Console.WriteLine("main finished {0}", sum);
Console.WriteLine("remaining {0}", barrier.ParticipantsRemaining);
For a locking mechanism to allow multiple readers, but just one writer, for a resource, the class
ReaderWriterLockSlim can be used. This class offers a locking functionality in which multiple readers can
access the resource if no writer locked it, and only a single writer can lock the resource.
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