Add optional support for GPU page faults in SYCL2020 and OMP backends

[ifdu]

No description provided.

[tomdeakin]

The OpenMP version needs to use the requires(unified_shared_memory) directive for correctness according to the standard. Please can you update the change to use this?

I do not believe the SYCL change here is standards compliant to SYCL 2020. Please can you remove this change.

[ifdu]

@tomdeakin Thanks for reviewing.

Sure, let me add that directive to the OpenMP version.

The SYCL change is an attempt to make use of [1]:

In the most capable systems, users do not need to use SYCL USM allocation functions to create shared allocations. The system allocator (malloc/new) may instead be used. Likewise, std::free and delete are used instead of sycl::free.

Would you have a recommendation to make it compliant?

[1] https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#_usm_allocations

[tomdeakin]

Good point, thanks for reminding me of that sentence. I don't think SYCL has a way to programmatically check for system capability, so the solution you have is probably as good as we can do for now. Thanks!

[ifdu]

@tomdeakin This pull request is now rebased on UoB-HPC:develop and includes the OpenMP directive which was missing.

[tomdeakin]

SYCL changes are fine. Just one query about the OpenMP is_device_ptr clause I added to a comment. Thanks for working through this!

[ifdu]

@tomdeakin I pushed a new OpenMP version without is_device_ptr, which works fine in my tests.

[tomdeakin]

Something is causing the CI to fail vs the develop branch (https://github.com/UoB-HPC/BabelStream/actions/runs/21986408147/job/63521614186). I will try to investigate.

[ifdu]

Does it come from the change or from the CI environment itself?

[tomdeakin]

Looks like the environment.