Hi Guys, I’ve been thinking about threading in games recently since the switch to multi-core processors. I've done concurrent programming at University so I know what problems can arise. But I only have experience with Java threading. And only want to deal with monitors when using shared resources. I'll be using ANSI C++ for implementation. I've got a few questions: 1. What would be the best multi-platform threading approach? I'd like my code to be as portable as possible. Would I just use OS specific preprocessor directives to include the appropriate implementations? This is how I am currently proposing to implement my threads at the moment. 1b. What about using .NET threads? What would the performance of running unmanaged code in a .NET thread be like? 2. What elements of my game could I thread? I've been thinking about this & the main candidate for threading would be AI. Are there any other sub-systems that would be good candidates to thread? Using threads for sub-systems would give rise to synchronization problems though? 2b. Will the main performance increase come from threading at the algorithm level? E.g. using 2 separate threads for calculating weights of 2 branches of a tree? If this is the case then programming games will be very difficult as the game world would become a shared resource & I would have to use monitors? They are hard to implement & hard to debug. Any suggested reading? Books or articles? Thanks for any advice given!

Hi samuraicrow,

I want to develop for both Java & C++. But at the moment I'm concentrating on C++. I want to make my renders in OpenGL so C++ is the way to go. I know there are OpenGL bindings for Java. I'll be looking into that ASAP. But I want to get my C++ skills in order first.

Thanks for your suggestions!

The SC++L may not be strictly thread-safe, but C++ is still the language of choice for most multithreading applications today. (Just look at GNU/Linux.)

In answer to Cacks:

1. I would highly recommend boost::threads for your multi-platform threading. It's tried and true and a large number of others here at GameDev will recommend it to you also.

1b. I can't speak to this myself from experience, but I've heard that unmanaged C++ gets a pretty noticeable slowdown when mixed with managed.

2. There are many elements of your game engine that you could thread, but I would actually recommend conservativeness in that area, because more threads can incur a performace cut on the system and the game overall, as well as being exponentially more difficult to debug. In practice, many games and engines end up with about 3 total threads -- the main thread, which handles all the updating and rendering, a "timer" thread which handles callbacks and time-related messages and events, and a "loader" thread which spools data from files as necessary. Data loading is the most common use of a separate thread in games.

2b. Probably not. This would as you observed be quite difficult to implement, and even then would not in most cases gain you much of an increase. Most performance increases through threads are not "performance increases" per se, but a way of processing data concurrently such that when you need it, it's ready and when you don't or it isn't, you can continue with other tasks. Threads tend to be more useful at a functional level, where you interface with the rest of the computer's hardware (such as the hard drive or the graphics card).

Hope this helps,
Twilight Dragon