[erlang-questions] game engines?

BOUDEVILLE Olivier <>
Tue Sep 20 15:36:17 CEST 2016


Hi,

In a somewhat related topic (large-scale discrete event simulation in Erlang) - and even it is a shameless plug, sorry for that - there is also Sim-Diasca (http://sim-diasca.com/), a discrete event simulation engine released as free software. The goal is to perform the simulation of complex systems in a multi-agent way, with scalability in mind (thus in a parallel and distributed manner); of course simulation and game engines share quite a lot of architectural and software traits.

As for us, we used (and are still using) plain Erlang (not OTP, whether or not it is a good choice) and a lightweight layer above it to provide the object-oriented constructs we needed (multiple inheritance, polymorphism, etc.), on top of which the engine as such was built (to perform time synchronisation, support interactions and provide relevant properties like the respect of causality and reproducibility).

In this setting each model instance is represented by exactly one Erlang process, and it proved to be quite scalable (of course synchronisation has a cost, and surely one shall not expect perfect speed-up with this kind of simulations). Back in 2010, we already exceeded 1 million interacting model instances in a single simulation (and the models involved were not specifically lightweight…). Recently this work received a bit of third-party positive feedback [1].

So IMHO such use of Erlang seems to be a very good solution to cover the needs you mentioned (moreover using it for that did not inflict much headache).

Hope this helps,

Olivier.

[1] http://sbrc2016.ufba.br/downloads/Salao_Ferramentas/154234.pdf

Olivier Boudeville
EDF R&D, Département SINETICS, Groupe ASICS, Bureau O2-E10
7, Boulevard Gaspard Monge, 91120 Palaiseau, France

Tél. : +33 (0)1 78 19 43 63
Tél. mobile : +33 (0)6 16 83 37 22


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Objet : Re: [erlang-questions] game engines?

2016-09-19 17:55 GMT+02:00 Miles Fidelman <<mailto:>>
I'm actually thinking about military simulation - where the model is essentially:

- every simulator (e.g., a flight sim, or a tank) is running on its own machine, complete with local world model and image generation (necessary to keep up with jitter-free image generation during high-g turns - you don't want pilots to puke all over the simulators)

- there's a lot of dead reckoning going on locally - the only things that cross the network are deltas and events, generally sent by multicast

- everything is synchronized by GPS time-stamp

I discovered Erlang when I realized that we (the company I worked for) took a very different approach for simulating "virtual forces" (think non-player characters) - when we simulated 1000 tanks, on one machine, each tank would be an object, and we had 4 threads winding their way through every object, 20 time a second.  Turns out that the main loops are real spaghetti code that breaks every time a new property gets added to an object.

I started wondering why we didn't just have a process per simulated object - essentially the way we treated the person-in-the-loop simulators.  The answer, of course, being context switching overhead.

Then, I discovered Erlang.  And I started thinking - why not just have a process per object.

Back in the day, there was the Sim94 troop simulation project, which was pretty successful - and way before Erlang got multicore support:
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.52.6023

This related master's thesis might also be of interest (oops, turns out I was the examiner):
https://www.scribd.com/document/184935294/Design-Patterns-for-Simulations-in-Erlang
I also found this newer work while searching, but I haven't read it myself:
https://www.researchgate.net/publication/233985869_Parallel_Discrete_Event_Simulation_with_Erlang
Finally, I found this, which made me double-check that I wasn't answering a post from 2012 :-) http://erlang.org/pipermail/erlang-questions/2012-March/065136.html

    /Richard



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