ReactiveECS.jl v2.0.0: Breaking Changes for Massive Performance Boosts

Gesee
Tue, 08 Jul 2025 19:01:48 +0000
Package Announcements

Hi everyone!

I’m happy to present ReactiveECS.jl v2.0.0! For those unfamiliar with the package, you can check out the original post.

This new version follows v1.0.0, which received heavy criticism on the Flecs Discord—but those critiques gave me valuable insight on how to drastically improve both speed and architecture.

What’s Changed

The core philosophy of the package remains: systems are reactive and can run asynchronously or in parallel, completely independent from each other. You can dynamically add/remove systems at runtime and even inject them into a live pipeline.

The main evolution lies in how data is stored, introducing a unique feature: partitioning.

Partitioning: Efficient Archetype Layout

Each archetype is now represented as a range within a central storage table, which dramatically reduces memory fragmentation and makes pooling straightforward. Here’s a conceptual illustration:

        INTERNAL STORAGE
 _______________________________________________________
|   |     Health    |     Transform    |    Physic     |
|-------------------------------------------------------
|   |      hp       |    x    |    y   |   velocity    |
|-------------------------------------------------------
| 1 |     100       |   1.0   |  1.0   |      //       |
|-------------------------------------------------------
| 2 |     150       |   1.0   |  1.0   |      //       |
|-------------------------------------------------------
| 3 |     ___       |   ___   |  ___   |      //       |
|-------------------------------------------------------
| 4 |     ___       |   ___   |  ___   |      //       |
|-------------------------------------------------------
| 5 |     50        |  -5.0   |  1.0   |     1.0       |
|-------------------------------------------------------
| 6 |     50        |  -5.0   |  1.0   |     1.0       |
|-------------------------------------------------------

Rows 1–4: partition for entities with Health and Transform

Rows 1–2 are active, 3–4 are pooled

Rows 5–6: partition for entities with Health, Transform, and Physic

This design allows:

Very fast entity creation

Simple pooling (just invalidate IDs outside of range)

Efficient component add/remove via internal swaps

New API Example

using ReactiveECS

@component Health begin
   hp::Int
end

@component Transform begin
    x::Float32
    y::Float32
end

@component Physic begin
   velocity::Float32
end

@component Status begin
    dirty::Int
end

@system PhysicSystem

function ReactiveECS.run!(world, ::PhysicSystem, query)

    # Getting components, the API for this may change in the future but this will always works
    transforms = get_component(world, :Transform)
    physics = get_component(world, :Physic)
    x = transforms.x
    velocities = physics.velocity

    for partition in query

      # We get every entities range matching our query
      zones::Vector{TableRange} = partition.zones
      for zone in zones
         range = get_range(zone)

         # Your optimizations (@inbounds, @threads, @simd, @turbo, etc.)
         for i in range
            x[i] += velocities[i]
         end
      end
   end
end

ecs = ECSManager()
register_component!(ecs, Health)
register_component!(ecs, Transform)
register_component!(ecs, Physic)
register_component!(ecs, Status)

e = create_entity!(ecs, (Health = Health(50), Physic = Physic(0.0), Transform = Transform(0,0)))

# Then this can be processed normally.
q = @query(ecs, Transfor & ~Status)

physic_sys = PhysicSystem()

subscribe!(ecs, physic_sys, @query(ecs,Transform & Physic))

run_system!(physic_sys)

dispatch_data(ecs) # Will call every system
blocker(ecs) # To wait for alll systems to finish if necessary.

Notes:

OR (|) in queries is not supported and likely never will be.
Why? Because components can be accessed at any time, so complex query logic isn’t needed.

Performance Benchmarks

Test Configuration:

CPU: Intel Pentium T4400 @ 2.2 GHz

RAM: 2 GB DDR3

OS: Windows 10

Julia: v1.10.5

Threads: 2

Reference benchmarks: https://github.com/abeimler/ecs_benchmark

Only creation and deletion are compared.
“Update” benchmarks have known issues and were excluded.

Operation | ReactiveECS v2 | Notes
Create 1 entity (2 components, initialized) | 1.21 µs | Fastest among tested ECSs
Create 1 entity (2 components, uninitialized) | 603 ns | Fastest overall
Create 10k entities (initialized) | 5.5 ms | ~3.7× faster than Overseer
Create 10k entities (uninitialized) | 70 µs | Best in class
Delete 1 entity (2 components) | 834 ns | Fastest deletion
Create a query | 3.3 µs | Scales with archetypes, negligible
Update 1k entities (translation) | 1.5 µs | 18× faster than Overseer
Update 100k entities (translation) | 145 µs | vs. 2.7ms for Overseer, 163µs for v1

ReactiveECS v2 is well-suited for handling millions of entities efficiently.

Known Limitations

Higher memory usage: Central table layout means every entity reserves slots for all components, even unused ones.

Parallelism isn’t finalized: Race conditions can still happen when modifying data during system execution or memory swaps. This will be addressed soon.

Contributions Welcome

Feel free to:

Look at the source

File issues

Open PRs

You will be able to use the package very soon.
More docs, comparisons, and tutorials are coming soon.

And if you like the project, a on GitHub is always appreciated!

Summary

ReactiveECS v2 brings a major architectural improvement, top-tier performance, and a clear API, all while staying reactive and dynamic. Whether you’re building simulations, games, or experiments, this ECS is built to scale.

Let me know what you think! Feedback, questions, and challenges are welcome.

4 posts - 2 participants