Freyr¶

Freyr is a high-performance, multithreaded Entity-Component-System (ECS) library for C++23, designed for real-time simulations and games.

Its core idea is simple: organize entities into archetype chunks — contiguous memory blocks grouped by component signature — and distribute those chunks across a thread pool as independent tasks. The result is predictable cache behaviour and straightforward parallelism without manual synchronization.

Highlights¶

High performance by design

Entities are stored in contiguous archetype chunks, minimising cache misses. Two scheduling strategies let you tune between cache affinity and load balancing.

Simple, composable API

Fluent builder pattern throughout — configure components, systems, and options with a single, readable call chain.

Built-in multithreading

ForEachAsync distribute chunk processing across a lock-free thread pool with zero boilerplate.

Decoupled event system

Thread-safe publish/subscribe bus lets systems communicate without direct dependencies.

At a glance¶

#include <Freyr/Freyr.hpp>

struct Position : fr::Component { float x, y, z; };
struct Velocity : fr::Component { float dx, dy, dz; };

class MovementSystem : public fr::System {
public:
    explicit MovementSystem(const Ref<fr::Scene>& scene) : System(scene) {}

    void Update(float dt) override {
        mScene->ForEachParallel<Position, Velocity>(
            [dt](fr::Entity, Position& pos, Velocity& vel) {
                pos.x += vel.dx * dt;
                pos.y += vel.dy * dt;
                pos.z += vel.dz * dt;
            });
    }
};

int main() {
    auto app = skr::ApplicationBuilder()
        .AddExtension<fr::FreyrExtension>([](fr::FreyrExtension& freyr) {
            freyr
                .WithOptions([](fr::FreyrOptionsBuilder& opts) {
                    opts.WithMaxEntities(1'000'000).WithThreadCount(8);
                })
                .WithComponent<Position>()
                .WithComponent<Velocity>()
                .WithSystem<MovementSystem>();
        })
        .Build<MyApp>();

    app->Run();
}

Requirements¶

Requirement	Minimum version
C++ standard	C++23
CMake	3.29
GCC	13
Clang	16
MSVC	19.37

Next steps¶

Installation — add Freyr to your project with CMake FetchContent
Quick Start — build a full example in minutes
ECS Overview — understand the concepts behind the library