ECS and Determinism

Hi,

I am developing a multiplayer strategy game and relying entirely on determinism to make sure simulation is equal across players. I just send the player inputs across the network and clients have to simulate the game using a lockstep. I really enjoy the ECS paradigm, but I felt that if I were to use the ECS, the whole nature of it not having a deterministic execution order and etc would make determinism impossible. Is there a currently a way to use the ECS and Job system in an entirely deterministic way, even if that means only using one thread or something like that?

Currently I have 2 "layers" to my game. Network synced systems (need to be 100% deterministic) which calculate every decision for everything, and Local systems, which do basically visuals, interpolation based on networked decisions, etc etc... would be awesome if I could have Network synced systems running 100% deterministically on the main thread or something like that and the other systems running however the hell they want, but I get a feeling that currently it is impossible to achieve?

At any rate, excited to see the system, cant wait to see it grow and to use it in other projects if I cant use it in this one,
Best,
Allan

 

ECS is designed to be eventually deterministic, it might be you are too early. Did you test the mathematics library for determinism?

 

So far I'm working around using only fixed point for my network synced systems. I don't use physics and game logic doesn't rely on animations or anything of the like so even though its a bit of headache at times, I've been able to keep it deterministic thus far.

 

Very excited about it. I am building an RTS demo which needs multiple worlds, but has no clue how to transfer information from simulation world to presentation world. What would be the mechanism in future?

 

Cool! Will try it definitely. My another problem is that I want to run different worlds at different frame rates. For instance, the simulation runs at a low and fixed frame rate and the presentation world runs at the target frame rate. Is there any way I can do that for now except executing systems manually?

 

In addition to this, I would also like to know if it is possible or if there are any plans to be able to manually control the update loop of a particular world (eg not only a single system, let unity still handle the update order of individual systems).

For example, I would like to be able to pause and/or speed up the simulation speed based on player input.

 

Does this mean that when I use producer Job which writes into container (e.g. concurrent queue), it will be deterministic no matter what number of threads it will run on?

Does it work like this?
Thread A processes entities 0-99 and writes 10 pieces of data into container section 0
Thread B processes entities 100-199 and writes 5 pieces into container section 1
Thread C processes entities 200-299 and writes 20 pieces into container section 2
Thread A again processes entities 300-350 and writes 4 pieces into container section 3
...

Then when reading on main thread, will I read "by sections"?
That means 10 pieces, 5 pieces, 20 pieces, 4 pieces even that Thread A,B and C might write data simultaneously?

 

NativeQueue.ParallelWriter is non-deterministic. NativeStream and EntityCommandBuffer are deterministic though and will probably meet your needs.