How to call bursted IJob.Run() from managed C# thread?

Unity Engine
, , , ,
1

Hi everyone

I’m trying to adjust plugin from the Asset Store to improve performance. This plugin uses default C# managed threads for better UX so that Editor doesn’t freeze while data is generating.

I found bottlenecks in the generation process and want to replace them with burst compiled code.

But I cannot run burst compiled code from C# managed thread.
When I’m running this code from thread:

var job = new MyCustomJob(){ ... }; // this is just IJob
job.Run();

I’m getting this error:
UnityException: CreateJobReflectionData can only be called from the main thread.

Sadly, calling job.Execute(); runs non-bursted job which is even worse than plain C# implementation.

I can’t use FunctionPointers because I’m heavily using NativeArrays which are forbidden with FunctionPointers.
For the same reason I can’t use this approach from Burst docs:
https://docs.unity3d.com/Packages/com.unity.burst@1.7/manual/docs/CSharpLanguageSupport_Lang.html#directly-calling-burst-compiled-code

I’m not trying to do something fancy, just to run(not schedule or smth tricky) burst compiled code from a managed thread. And I don’t mind wrapping code with Jobs to be able to use NativeArrays, but this just doesn’t work.

Any help or suggestions, please?

2

You “can” use native arrays together with directly calling burst compiled code, it’s just that it might be smart to wrap it. Here’s an example:

[BurstCompile]
public static class MyBurstWrapper
{
        // Nice safe interface that others call
        public static unsafe int Sum(NativeArray<int> values)
        {
            Sum((int*)values.GetUnsafePtr(), values.Length, out var result);
            return result;
        }

        // Burst compiled implementation using pointers.
        [BurstCompile]
        private static unsafe void Sum(int* values, int count, out int result)
        {
            var res = 0;
            for (int i = 0; i < count; i++)
                res += values[i];
            result = res;
        }
}

Other parts of the Collections package (if you use that) also gives access to the underlying implementation (like NativeList.GetUnsafeList) which you can send to burst functions as pointers.

1 Like