Monday, April 11, 2011

Function list for parallel - My journey to Parallel extension

Today I want to share my failure.. :-). Sometimes the failure make me "better experience"...

These days I am struggling the design patterns and parallel as I claimed design pattern is not parallel friendly. I bet a lot of people won't agree with me. Give me some time and let me think through it.

Let me explain the context; otherwise, you will doubt the rationale behind my test. I found many parallel algorithm or approach is trying to partition the data. how about play function (not data) to achieve parallelism?

Since I am a fan of F#, I really hope the function way will win. Let us wait and see.. :)

the code is

  • The first version is to partition data and make parallel. 
  • The second version is to apply a function list to the data. 

static void Main(string[] args)
        {
            List< double > a = new List< double >();
            List < double > b = new List < double >();
            Stopwatch sw = new Stopwatch();
            var size = 100000;

            for (int j = 0; j < 100; j++)
            {

                var l = Enumerable.Range(0, size).ToList();
                sw.Reset();
                sw.Start();
                Parallel.For(0, size, i => l[i]++);
                sw.Stop();
                a.Add(sw.ElapsedMilliseconds);

                var f = Enumerable.Range(0, size).Select(i => { return (() => l[i]++); }).ToList();
                sw.Reset();
                sw.Start();
                Parallel.ForEach(f, n => n.Invoke());
                sw.Stop();
                b.Add(sw.ElapsedMilliseconds);

            }

            a.Zip(b, (x, y) => new { x, y }).ToList().ForEach(n => Console.WriteLine("{0}, {1}", n.x, n.y));
        }

First of all, why I need to run 100 times? Parallel is based on some random factor, if we only run once, the result is not accurate. 

The results shows data partition version wins.. :-(

the first version is so simple, so the second version's function invoke fails me.. (sigh). But anyway I tried my luck.. 

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