Hacker News new | ask | show | jobs
by mikhmha 248 days ago
In the case of Call of Duty: Black Ops 1. Thee matchmaking + leaderboards system was implemented by DemonWare (3rd party) in Erlang.

Erlang actually has good enough performance for many types of multiplayer games. Though you are correct that it may not cut it for fast paced twitch shooters. Well...I'm not exactly sure about that. You can offload lots of expensive physics computations to NIF's. In my game the most expensive computation is AI path-finding. Though this never occurs on the main simulation tick. Other processes run this on their own time.
1 comments
array_key_first 248 days ago
The biggest hurdle to a game server written entire on the BEAM is the GC. GC pauses just take too much time, and when you need to get out (for example) 120 updates per second, you can't afford it. Even offloading stuff to C or C++ does not save you, because you either have to use the GC, do a copy, or both.

Game servers typically use very cheap memory allocation techniques like arenas and utilize DOD. It's not uncommon for a game server simulation to be just a bunch of arrays that you grow, never shrink, and then reset at the end of the game.

link
mikhmha 247 days ago
Good point. Yeah I guess it wouldn't cut it for any fast-paced twitch shooter. Especially with a 120 update per second deadline. A non-deterministic GC pause could have disastorous effects, especially in a tense shootout. I don't know much about GC theory but the GC in BEAM is per process and heap-based? I'm not sure exactly what that entails, but can you not structure the main simulation process to take advantage of this fact?

I find myself interested in developing multi-player simulations with more flexible deadlines. My MMO runs at 10 ticks. And its not twitch-based. So the main simulation process can have pauses and it wouldn't have a big impact on gameplay. Though this has never occurred.

As long as: (tick process time) + (send update to clients) + (gc pause) < 100ms, everything is fine?. (My assumption).

Btw what does DOD mean? Is it Data on Demand? Since my game is persistent I can't reset arrays at some match end state. So I store things either in maps on the main server process or I store it in the dedicated client process state (can only be updated via server process).

link