ijobentity-parallel-job

IJobEntity — Parallel Job

Intent

Execute per-entity computation in parallel across worker threads using a source-generated job whose query is inferred from the Execute method signature.

Use When

Per-entity work that is parallelizable, Burst-friendly, and does not require chunk-level control. The primary pattern for simulation logic in production DOTS.

Avoid When

You need chunk-level early-exit, direct chunk pointer access, or change filtering via chunk.DidChange() — use IJobChunk. Avoid when the job needs ECB.ParallelWriter without [ChunkIndexInQuery] — add the parameter first.

Senior Pattern

• partial struct MyJob : IJobEntity with [BurstCompile].
• Execute signature declares read/write intent: ref = write, in = read.
• Schedule with state.Dependency = new MyJob { ... }.ScheduleParallel(state.Dependency).
• Use [WithAll], [WithNone], [WithAny] attributes on the struct for query filtering.
• Add [ChunkIndexInQuery] int chunkIndex to Execute when ECB.ParallelWriter is needed.

Code Template

[BurstCompile]
partial struct ApplyVelocityJob : IJobEntity
{
    public float DeltaTime;

    void Execute(ref LocalTransform transform, in Velocity velocity)
    {
        transform.Position += velocity.Value * DeltaTime;
    }
}

[BurstCompile]
public void OnUpdate(ref SystemState state)
{
    state.Dependency = new ApplyVelocityJob
    {
        DeltaTime = SystemAPI.Time.DeltaTime
    }.ScheduleParallel(state.Dependency);
}

Anti-Patterns

• Forgetting to assign the return of Schedule to state.Dependency — next system races against this job.
• Using ScheduleParallel with a non-parallel ECB — safety exception at runtime.
• Capturing a NativeContainer without [ReadOnly] when it is read-only — false write dependency.
• Using Schedule (single-threaded) when ScheduleParallel is safe — wastes parallel budget.

Runtime Risks

• Missing state.Dependency chain: data race between this job and subsequent systems.
• ECB.ParallelWriter without sort key: non-deterministic command order, potential exception.