Simulation Core

Architecture of the Rust simulation engine

February 4, 2026

Simulation Core

The simulation engine is written in Rust and compiles to both native binaries and WebAssembly for browser execution.

Architecture Overview

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flowchart LR
    subgraph Input
        Config[Configuration]
        Rotation[Rotation]
        Data[Game Data]
    end
 
    subgraph Engine
        Sim[Simulation Loop]
        Events[Event Queue]
        State[Combat State]
    end
 
    subgraph Output
        Metrics[Metrics]
        Timeline[Timeline]
    end
 
    Config --> Sim
    Rotation --> Sim
    Data --> Sim
    Sim --> Events
    Events --> State
    State --> Sim
    Sim --> Metrics
    Sim --> Timeline

Core Components

Component	Responsibility
Configuration	Character stats, talents, gear, encounter parameters
Rotation	Priority list defining ability usage
Game Data	Spell definitions, coefficients, scaling formulas
Event Queue	Priority queue of pending game events
Combat State	Current buffs, debuffs, resources, cooldowns
Metrics	DPS, resource usage, ability breakdowns

Determinism

The engine produces identical results given identical inputs:

Seeded random number generator for all stochastic events
Deterministic floating-point operations
Sorted iteration over collections
No dependency on system time or external state

This enables distributed simulation where chunks can be processed by any node and results aggregated reliably.

WASM Integration

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The engine compiles to WebAssembly using wasm-pack:

bash

cd crates/engine
wasm-pack build --target web --out-dir ../../packages/wowlab-engine/wasm

The generated WASM module is loaded asynchronously in the browser and provides the same API as the native binary.

Next steps

Combat Mechanics

Architecture Overview

flowchart LR
    subgraph Input
        Config[Configuration]
        Rotation[Rotation]
        Data[Game Data]
    end
 
    subgraph Engine
        Sim[Simulation Loop]
        Events[Event Queue]
        State[Combat State]
    end
 
    subgraph Output
        Metrics[Metrics]
        Timeline[Timeline]
    end
 
    Config --> Sim
    Rotation --> Sim
    Data --> Sim
    Sim --> Events
    Events --> State
    State --> Sim
    Sim --> Metrics
    Sim --> Timeline

Core Components

Component	Responsibility
Configuration	Character stats, talents, gear, encounter parameters
Rotation	Priority list defining ability usage
Game Data	Spell definitions, coefficients, scaling formulas
Event Queue	Priority queue of pending game events
Combat State	Current buffs, debuffs, resources, cooldowns
Metrics	DPS, resource usage, ability breakdowns

Determinism

The engine produces identical results given identical inputs:

Seeded random number generator for all stochastic events

Deterministic floating-point operations

Sorted iteration over collections

No dependency on system time or external state

This enables distributed simulation where chunks can be processed by any node and results aggregated reliably.

WASM Integration

The engine compiles to WebAssembly using wasm-pack:

bash

cd crates/engine
wasm-pack build --target web --out-dir ../../packages/wowlab-engine/wasm

The generated WASM module is loaded asynchronously in the browser and provides the same API as the native binary.