TR Forum Tidings: Game engine multithreading gains
TR forum member UberGerbil has put together a rather interesting post
about the diminishing performance returns of multithreading in games. With Intel and AMD scrambling to bring quad-core processors to the market, and Intel intending to scale up to tens and even hundreds of cores in the coming years, gamers who shell out big bucks for the latest multi-core chips will be expecting high performance gains in future game titles. However, as UberGerbil explains, Amdahl's law states that code that cannot be fully parallelized—such as a game engine—receives diminishing performance returns from scaling to an increasing number of cores.
In UberGerbil's example, a hypothetical game engine that can stay 90% parallelized with an infinite number of cores will get a 1.8x speedup with two cores, a 3.08x speedup with four cores, a 4.7x speedup with eight cores, and a 6.4x speedup with 16 cores. Since fully scalable 90% parallelism is a very optimistic scenario for a game, future real-world numbers may turn out to be much grimmer. If you have any insights to share or questions to ask about Amdahl's law or multithreading in general, feel free to sign up for a forums account and join the discussion.