How do I create nested loop IJobParallelFor?

Hello. I want to create a grid of some entities with ecs. Each entity should have component GridComponent that contains two ints x and y. How do I implement a job and jobcomponentsystem for it

 

I have simple test ECS job system example here
Unity ECS basics Hybrid Pure Job Systems examples
https://forum.unity.com/threads/ecs-with-3-very-basics-hybrid-pure-and-job-system-examples.545131/

This may be useful for you, to get started.

 

Thanks it was useful. I noticed that you derive you job class from IJob and passing only one argument to the .Schedule(). I'm using IJobParralelFor and passing 3 params. Is there any difference between them?

 

one works in parallel with itself and the other doesn't. Ideally you use IJobParallelFor whenever you can for performance.

IJob allows you to schedule a single job that runs in parallel to other jobs and the main thread.
https://docs.unity3d.com/2018.1/Documentation/ScriptReference/Unity.Jobs.IJob.html

Parallel-for jobs allow you to perform the same independent operation for each element of a native container or for a fixed number of iterations.
When Scheduled the job's Execute(int index) method will be invoked on multiple worker threads in parallel to each other.
https://docs.unity3d.com/2018.1/Documentation/ScriptReference/Unity.Jobs.IJobParallelFor.html

 

You can do the first for loop jobbed, and then do the inner for normally.

You will probably want to make a flat array, as you can't have a nested NativeArray.

This code is just written from memory, but should give you an idea of how it works.

Code (CSharp):

1. struct VelocityJob : IJobParallelFor
2.     {
3.        
4.         public NativeArray<GridComponent> yourArray;
5.  
6.         // The code actually running on the job
7.         public void Execute(int i)
8.         {
9.             int size = yourArray.length;
10.             for(int j = 0; j < size; j++)
11.             {
12.                GridComponent component = yourArray[i * size + j];
13.             }
14.         }
15.     }

But you might run into some problems, where you are not allowed to read from some of the entities, as each thread is only allowed access to a part of the whole data.
You can get around that, by making your array ReadOnly, but that only works if you don't need to write to them.

I don't have a solution to all this right now, but I hope this will help you get started.

 

READ ONLY FTW!! Efing brilliant! Thank you.