IJob

Description

IJob allows you to schedule a single job that runs in parallel to other jobs and the main thread.

When a job is scheduled, the job's Execute method will be invoked on a worker thread. The returned JobHandle can be used to ensure that the job has completed. Or it can be passed to other jobs as a dependency, thus ensuring the jobs are executed one after another on the worker threads.

using UnityEngine;
using Unity.Collections;
using Unity.Jobs;

class ApplyVelocitySample : MonoBehaviour
{
    struct VelocityJob : IJob
    {
        // 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 on the same frame or the next frame, but the job should
        // perform work in a deterministic and independent way when running on worker threads.
        public float deltaTime;

        // The code actually running on the job
        public void Execute()
        {
            // Move the positions based on delta time and velocity
            for (var i = 0; i < position.Length; i++)
                position[i] = position[i] + velocity[i] * deltaTime;
        }
    }

    public void Update()
    {
        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 VelocityJob()
        {
            deltaTime = Time.deltaTime,
            position = position,
            velocity = velocity
        };

        // Schedule the job, returns the JobHandle which can be waited upon later on
        JobHandle jobHandle = job.Schedule();

        // Ensure the job has completed
        // It is not recommended to Complete a job immediately,
        // since that gives you no actual parallelism.
        // You optimally want to schedule a job early in a frame and then wait for it later in the frame.
        jobHandle.Complete();

        Debug.Log(job.position[0]);

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

Public Methods