IJobForExtensions

Description

Contains extension methods for jobs implementing the IJobFor interface.

The methods in this extension class add an instance of a job to the work queue, while IJobFor.Execute defines how to perform an asynchronous task. Use IJobForExtensions.ScheduleByRef to request asynchronous execution, or IJobForExtensions.RunByRef to execute the job immediately on the main thread.

Additional resources: IJobFor.

struct ApplyVelocityJobFor : IJobFor
{
    // Jobs declare all data that will be accessed in the job
    // By declaring it as read only, multiple jobs are allowed to access the data in parallel
    [ReadOnly]
    public NativeArray<Vector3> velocity;

    // By default containers are assumed to be read & write
    public NativeArray<Vector3> position;

    // Delta time must be copied to the job since jobs generally don't have concept of a frame.
    // The main thread waits for the job same frame or next frame, but the job should do work deterministically
    // independent on when the job happens to run on the worker threads.
    public float deltaTime;

    // The code actually running on the job
    public void Execute(int i)
    {
        // Move the positions based on delta time and velocity
        position[i] = position[i] + velocity[i] * deltaTime;
    }
}

public void ApplyVelocity_For(bool scheduleParallel)
{
    var position = new NativeArray<Vector3>(500, Allocator.Persistent);

    var velocity = new NativeArray<Vector3>(500, Allocator.Persistent);
    for (var i = 0; i < velocity.Length; i++)
        velocity[i] = new Vector3(0, 10, 0);

    // Initialize the job data
    var job = new ApplyVelocityJobFor()
    {
        deltaTime = Time.deltaTime,
        position = position,
        velocity = velocity
    };

    // If this job required a previous job to complete before it could safely begin execution,
    // we'd use its handle here. For this simple case, there are no job dependencies,
    // so a default JobHandle is sufficient.
    JobHandle dependencyJobHandle = default;

    JobHandle velocityJobHandle = default;
    if (scheduleParallel)
    {
        // Schedule job to run on multiple worker threads, attempting to distribute work items evenly between them.
        // First parameter is how many for-each iterations to perform.
        // The second parameter is the batch size,
        //   essentially the no-overhead innerloop that just invokes Execute(i) in a loop.
        //   When there is a lot of work in each iteration then a value of 1 can be sensible.
        //   When there is very little work values of 32 or 64 can make sense.
        // The third parameter is a JobHandle to use for this job's dependencies.
        //   Dependencies are used to ensure that a job executes on worker threads after
        //   the dependency has completed execution.
        velocityJobHandle = job.ScheduleParallelByRef(position.Length,
            64, dependencyJobHandle);
    }
    else
    {
        // Schedule job to run at a later point, processing all elements on a single worker thread.
        // First parameter is how many for-each iterations to perform.
        // The second parameter is a JobHandle to use for this job's dependencies.
        //   Dependencies are used to ensure that a job executes on worker threads after the dependency has completed execution.
        //   In this case we don't need our job to depend on anything so we can use a default one.
        velocityJobHandle = job.ScheduleByRef(position.Length, dependencyJobHandle);
    }


    // Ensure the job has completed.
    // It is not recommended to Complete a job immediately,
    // since that reduces the chance of having other jobs run in parallel with this one.
    // You optimally want to schedule a job early in a frame and then wait for it later in the frame.
    // Ideally this job's JobHandle would be passed as a dependency to another job that consumes the
    // output of this one. If the output of this job must be read from the main thread, you should call
    // Complete() on this job handle just before reading it.
    velocityJobHandle.Complete();

    // Once the job is complete, the expected processing should have occurred.
    for (var i = 0; i < velocity.Length; i++)
        Assert.AreEqual(Time.deltaTime * velocity[i].y, position[i].y);

    // Native arrays must be disposed manually.
    position.Dispose();
    velocity.Dispose();
}
.

Static Methods