Use of sycl::half, with CL/sycl.hpp SYCL header included

[sbalint98]

In #143, the half data types were replaced with sycl::half, while including the CL/sycl.hpp SYCL header. According to the SYCL specification section 4.3, when that header is included all SYCL types should exist inside the ::cl::sycl namespace.

Unfortunately, this change also breaks compilation with hipSYCL, since sycl::half is not defined. In order to solve this problem I see three possible solutions:

1. Use, like for all other SYCL types, the ::cl::sycl namespace for half as well
2. Move to the ::sycl namespace in case of all SYCL types, and include the sycl/sycl.hpp header instead of CL/sycl.hpp
3. Add a hipSYCL specific workaround similar to Add hipSYCL scope_handle and host_task #122 (comment)

I think the most consistent and least error-prone solution would be the first one. Can you give some feedback on what would be the preferred solution?

[mmeterel]

@sbalint98 Thanks for bringing up this issue. I wonder if option 2 is a viable option. Did you get a chance to try it with hipSYCL and DPC++?
@mkrainiuk Do you see any issues with option 2?

[sbalint98]

I'll have a look at option two and open a PR if it works

[sbalint98]

It looks to me that the sycl/sycl.hpp header is not part of the dpc++ 2021.4.0 release (installed by the oneAPI base toolkit install script, version: 2021.4.0.3422). I am a bit confused since this file have been merged into the dpc++ GitHub repo here: intel/llvm#3290 in March already. Can you help me with what I might be missing here?

If you can confirm that the sycl/sycl.hpp is indeed not part of the current release of dpc++, I think we can exclude option 2.

EDIT:
Tested option number one for checking #140, if you agree I will open a PR...

[mmeterel]

It looks to me that the sycl/sycl.hpp header is not part of the dpc++ 2021.4.0 release (installed by the oneAPI base toolkit install script, version: 2021.4.0.3422). I am a bit confused since this file have been merged into the dpc++ GitHub repo here: intel/llvm#3290 in March already. Can you help me with what I might be missing here?

If you can confirm that the sycl/sycl.hpp is indeed not part of the current release of dpc++, I think we can exclude option 2.

EDIT: Tested option number one for checking #140, if you agree I will open a PR...

Any chance you can send your branch so I can take a quick look before opening a PR?

[mmeterel]

1. se, like for all other SYCL types, the ::cl::sycl namespace for half as well

I looked at the 2021.4 release and indeed could not locate sycl/sycl.hpp. Sorry for the confusion with my comment. We can exclude option 2 as you suggested.

[sbalint98]

Any chance you can send your branch so I can take a quick look before opening a PR?

Sure, have a look at this branch: https://github.com/sbalint98/oneMKL/tree/fix-qualification-ver2

[mmeterel]

@sbalint98 After looking through your branch, I would actually prefer a hipSYCL specific solution like in option 3. Could we bring that one back? Sorry for the inconvenience.

[sbalint98]

No problem, added the change as requested to the PR #144

[mmeterel]

Closing issue. It is handled with option 3.