Parallelisation Talk Examples – ConcurrentDictionary

The example used in the talk was one I had already blogged about. The original blog entry the example was based upon is here: Parallelisation in .NET 4.0 – The ConcurrentDictionary.

Code Example

class Program
{
    private static ConcurrentDictionary<string, int> wordCounts =
        new ConcurrentDictionary<string, int>();

    static void Main(string[] args)
    {
        string[] lines = File.ReadAllLines("grimms-fairy-tales.txt");
        Parallel.ForEach(lines, ProcessLine);

        Console.WriteLine("There are {0} distinct words", wordCounts.Count);
        var topForty = wordCounts.OrderByDescending(kvp => kvp.Value).Take(40);
        foreach (KeyValuePair word in topForty)
        {
            Console.WriteLine("{0}: {1}", word.Key, word.Value);
        }
        Console.ReadLine();
    }

    private static void ProcessLine(string line)
    {
        var words = line.Split(' ')
            .Select(w => w.Trim().ToLowerInvariant())
            .Where(w => !string.IsNullOrEmpty(w));
        foreach (string word in words)
            CountWord(word);
    }

    private static void CountWord(string word)
    {
        if (!wordCounts.TryAdd(word, 1))
            UpdateCount(word);
    }

    private static void UpdateCount(string word)
    {
        int value = wordCounts[word];
        if (!wordCounts.TryUpdate(word, value + 1, value))
        {
            Console.WriteLine("Failed to count '{0}' (was {1}), trying again...",
                word, value);

            UpdateCount(word);
        }
    }
}

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