Simple demo of Parallel LINQ

output.txt

Parallel took:    00:00:00.4485898
Sequential took:  00:00:11.0775119
Parallel speedup: 24.69x

parallel-map-demo.cs

using System.Diagnostics;
namespace test_thread;

class Program
{
    static void Main()
    {
        var p = new Program();
        var goal = 100;
        var parallelTime = p.TimeParallel(Integers(), goal);
        Console.WriteLine($"Parallel took:    {parallelTime}");
        var sequentialTime = p.TimeSequential(Integers(), goal);
        Console.WriteLine($"Sequential took:  {sequentialTime}");
        var speedup = sequentialTime / parallelTime;
        Console.WriteLine($"Parallel speedup: {speedup:F2}x");
    }

    private TimeSpan TimeParallel(IEnumerable<int> inputData, int goal)
    {
        var mappedValues = inputData
            .AsParallel()
            .Select(SlowFunction);
        var sw = Stopwatch.StartNew();
        var found = mappedValues.Contains(goal);
        sw.Stop();
        Debug.Assert(found);
        return sw.Elapsed;
    }
    
    private TimeSpan TimeSequential(IEnumerable<int> inputData, int goal)
    {
        var mappedValues = inputData
            .Select(SlowFunction);
        var sw = Stopwatch.StartNew();
        var found = mappedValues.Contains(goal);
        sw.Stop();
        Debug.Assert(found);
        return sw.Elapsed;
    }
    
    
    private static IEnumerable<int> Integers()
    {
        for (var i = 0; true; ++i)
            yield return i;
    }

    private static T SlowFunction<T>(T value)
    {
        Thread.Sleep(100);
        return value;
    }
}