mach/ecs is an Entity Component System for Zig built from first-principles.

This is an experimental Mach library, according to our stability guarantees:

Experimental libraries may have their APIs change without much notice, and you may have to look at recent changes in order to update your code.

Why this library is not declared stable yet

• Initially a 100% clean-room implementation, working from first-principles. Later informed by research into how other ECS work, with advice from e.g. Bevy and Flecs authors at different points (thank you!)
• Solve the problems ECS solves, in a way that is natural to Zig and leverages Zig comptime.
• Fast. Optimal for CPU caches, multi-threaded, leverage comptime as much as is reasonable.
• Simple. Small API footprint, should be natural and fun - not like you're writing boilerplate.
• Enable other libraries to provide tracing, editors, visualizers, profilers, etc.

Under heavy development, not ready for use!

As development continues, we're publishing a blog series "Let's build an Entity Component System from scatch".

Join us in developing it, give us advice, etc. on Discord or follow updates on Twitter.

There are plenty of known issues, and things that just aren't implemented yet. And certainly many unknown issues, too.

• Missing multi-threading!
• Currently only handles entity management, no world management or scheduling. No global data, etc.
• Lack of API documentation (see "example" test)
• Missing hooks that would enable visualizing memory usage, # of entities, components, etc. and otherwise enable integration of editors/visualizers/profilers/etc.
• We have dense and sparse data, but no shared data yet.
• If many entities are deleted, iteration becomes slower due to needing to skip over entities in the free_slots set, we should add a .compact() method that allows for remediating this.
• If tons of entities are deleted, even with .compact(), memory would not be free'd / returned to the OS by the underlying components arrays. We could add a .compactAndFree() method to correct this.
• It would be nicer if there were configuration options for performing .compactAndFree() automatically, e.g. if the number of free entity slots is particularly high or something.
• Currently we do not expose an API for pre-allocating entities (i.e. allocating capacity up front) but that's very important for perf and memory usage in the real world.
• When entity is deleted, maybe via systems / an event/callback, need a way to be notified of destruction. Same with updated maybe.

See also the numerous TODOs in main.zig.