[SOLVED] IJobParallelfor + BurstCompiler: Can't copy value type from static field (see error msg))

The fix was no big deal, as I just passed the value via job arguments, but anyway I felt I should post it. I'm not sure if this error is intentional.

The ParallelForJob was completely empty at testing, despite this line (originally I did this with a custom struct, but for the sake of simplicity I demo this with an int):

Code (CSharp):

1. TestJob testJob = new TestJob();
2. JobHandle testJobHandle = testJob.Schedule(1000, 1);
3. testJobHandle.Complete();
4.  
5. ---
6.  
7. [BurstCompile]
8. private struct TestJob : IJobParallelFor
9. {
10. public void Execute(int i)
11. {
12. int intZero = MyStaticClass.intZero;
13. }
14. }
15.  
16. ---
17.  
18. public static class MyStaticClass
19. {
20. public readonly static int intZero = 0;
21. }

Error output (no more details, disabling burstcompiling removed the error):

System.InvalidOperationException: Jobs can only create Temp memory
This Exception was thrown from a job compiled with Burst, which has limited exception support. Turn off burst (Jobs -> Enable Burst Compiler) to inspect full exceptions & stacktraces.

It just seems odd to me, as I can use static mehtods too, but I'm not allowed to copy static values ?

EDIT:
Unity 2019.1.1.f.1
Burst 1.0.0
Jobs preview11-0.0.7

 

You can’t use static fields in Burst, except readonly/const fields.

 

He is actually reading from a static readonly field though

 

Oops my bad, missed bottom part

 

Anyway. It works fine in my case. Without any problems. (2019.1.1f1 Burst 1.0.1 Entites preview.31)


And in our game also all works fine.

 

Are you sure it's in this job and not in other job where you allocate native containers not with Allocator.Temp?

Cos in this case you'll see your error

 

Thanks for the feedback!

That's weird.I'm on 2019.1.1f1 and all packages are up to date regarding to the package manager. But are you sure burst is 1.0.1 ? mine is 1.0.0, and there are no updates available.

Also yes, I'm sure it's not from another job, I tested it extensively.

 

OK I just saw burst 1.0.1 is available: https://docs.unity3d.com/Packages/com.unity.burst@1.0/changelog/CHANGELOG.html

But I don't see an update in the package manager. Can I invoke that somehow ?

 

Enable Show preview packages

 

Then retest I shown you, when error comes. Or show full your code here.

 

I do have preview packages active all the time. no update for burst to 1.0.1 :-(

It's no big issue for me at all as I could fix it by passing the values via job arguments. I just wanted to report an eventual bug. maybe it's gone with 1.0.1, I will see when the update is available for me...

 

It works as before on 1.0.0 all the same

 

ok thanks for testing then...I did test it several times with the testjob on/off always the same result. I have no idea how this is possible...must be some very special circumstance not obvious to me. I guess I will test it in an empty project

 

@eizenhorn the secret is unveiled....

The reason for the error is a NativeArray (readonly & static, created in static constructor) in the same static class I copy the readonly struct/int/whatever from.

I wasn't aware that static constructors are called each time a static class member is accessed, if I understand the following correctly: https://stackoverflow.com/questions/1437352/when-is-a-static-constructor-called-in-c

Learned something

Code (CSharp):

1. TestJob testJob = new TestJob();
2. JobHandle testJobHandle = testJob.Schedule(1000, 1);
3. testJobHandle.Complete();
4.  
5. ---
6.  
7. [BurstCompile]
8. private struct TestJob : IJobParallelFor
9. {
10. public void Execute(int i)
11. {
12. int intZero = MyStaticClass.intZero;
13. }
14. }
15.  
16. ---
17.  
18. public static class MyStaticClass
19. {
20. public readonly static int intZero = 0;
21. public readonly static NativeArray<int> myNativeArray;
22.  
23. static MyStaticClass
24. {
25. myNativeArray = new NativeArray<int>(100, Allocator.Persistent);
26. }
27.  
28. }

 

As I told before Because error clearly says about native container allocation.

Nope, it's not true. Static constructor called once, and guaranteed it'll be before first access.

I think the problem (not actually problem, just by design) is how Burst works with static readonly values. I think in creates instances and copy to jobs when compile, and not acces to it by some static references. But it's only my things. I think @mike_acton or @Joachim_Ante or @xoofx explain it better

 

OK thanks for clarifying! I was curious about the static constructor call, as it would have been a huge overhead.

 

I don't think this is right. the static constructor (and static field initializers) should be called exactly once per app domain, if you use the class. if you are calling it multiple times it's a bug

e.g. in the following code

Code (CSharp):

1. class Foo {
2. public static int value;
3. }
4. class Bar {
5. public static readonly int value = ++Foo.value;
6. }

,

Bar.value

should be always 1, no matter how many jobs referencing Bar you have

 

I hit a really strange case of this today. Or rather strange in the side effects it causes. I setup a static constructor to call NavMesh.GetSettingsByIndex. So it got called by burst and shortly thereafter Unity locked up. Looked at the logs and saw a ton of calls from all over into unity api's, most not even our code, were complaining about not being on the main thread. ECS internal code like where it schedules jobs wasn't running on the main thread. Like the thread context just got completely screwed.

 

A irreverent noob question, I was wondering what's this static class use for, for something like storing user data? can you give me some insight about it? Thanks.

 

You can't access objects from within jobs if you want to use burst compiler. But it's allowed to directly access static readonly values and static methods, too.

 

For some global shared immutable data which filled from config on initialization