My first Parallel Computing programming experience

For some reason I have not researched on yet, processors aren’t evolving as fast as they did in the past. We don’t double the processor speed every 6 months like it used to be, so manufacturers are adding more processors to computers in order to gain a ‘little’ extra speed.

But what happens with your programs? will they take the advantage of more than one processor in your machine. The answer I would guess is “no, they don’t”, and if you’re working with the .net framework as I am, the answer is definitely NO. So if you want your programs to run smoother and take advantage of your computer’s processing power you’ll have to either learn a new parallel computing language or start playing around with the Parallel Computing extension for the .net Framework (like I did).

First let me tell you that if you’re used to work with threads (System.Threading) you’ll have no problem understanding the new parallel paradigm. When working with thread you would create one to say, calling a web service and not freezing the UI while doing it, right? well it’s the same thing here, instead of creating a new Thread you’ll create a new Task.

But this .net extension has another cool feature called PLINQ (Google it, I couldn’t find and official updated resource) which pretty much ease things for you. I’ll show you an example of this with something I did in my Goomez indexer.

So I had a function called IndexFiles that looked like this:

        private static void IndexFiles()
        {
            try
            {
                List<string> servers = GetConfigList(K_SERVERS);

                foreach (string server in servers)
                {
                    foreach (string folder in GetShares(server))
                    {
                        if (folder.EndsWith("$"))
                            continue;

                        string folderFullPath = @"\\" + server + @"\" + folder;

                        try
                        {
                            IndexFolder(folderFullPath);

and I wanted to change the outter foreach, which BTW that’s one of the team’s recommendations, so I switched to the following:

        private static void ParallelIndexFiles()
        {
            try
            {
                Parallel.ForEach<string>(GetConfigList(K_SERVERS), server =>
                {
                    foreach (string folder in GetShares(server))
                    {
                        if (folder.EndsWith("$"))
                            continue;

                        string folderFullPath = @"\\" + server + @"\" + folder;

                        try
                        {
                            ParallelIndexFolder(folderFullPath);

see how my foreach is different now? what that change in my code does, is that for each server in my list the code executed inside the lamda expression is processed by the first available processor… pretty cool uh?!

To try this stuff you can either download the CTP of Visual Studio 2010 and the .net Framework 4.0 or the Parallel Extension to the .net framework 3.5 June 2008 CTP.

Quick note: if you don’t have two (or more) processors you would end up slowing your program a little bit because there’s a little overhead which they say will be eliminated in next versions.