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IJobParallelFor.Execute

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Declaration

public void Execute(int index);

Parameters

index The index of the Parallel for loop at which to perform work.

Description

Performs work against a specific iteration index.

                        struct ApplyVelocityJobParallelFor : IJobParallelFor
{
    // 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_ParallelFor()
{
    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 ApplyVelocityJobParallelFor()
    {
        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;
    // 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.ScheduleByRef(position.Length,
        64, 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();
}

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