Workaround nearbyint() for Kokkos SYCL backend

[NamjaeChoi]

Kokkos does not provide portable nearbyint() implementation for SYCL backend.

[NamjaeChoi]

@lindsayad @roystgnr Objections?

[roystgnr]

Not a fan of us putting things in namespace Kokkos. No way to make this work via ADL?

[NamjaeChoi]

I don't think so. ADL does not apply to fundamental types

[roystgnr]

I'm not a fan of the MOOSE "you must file an issue before you can put up a PR" policy, but I think this is one case where it would have paid off; I'm instead trying to reverse-engineer what must be wrong here.

I take it Kokkos calls Kokkos::nearbyint() explicitly (so we can't change the call to a wrapper in our own namespace), in some function we can't reimplement to avoid the call, and Kokkos doesn't implement nearbyint() for one backend ... but isn't that missing implementation a bug report we should file or a PR we could submit there? As is, if we merge this PR and they do fix that backend, then won't we no longer be able to compile against the result, because the compiler will see two definitions?

[NamjaeChoi]

I'm not a fan of the MOOSE "you must file an issue before you can put up a PR" policy, but I think this is one case where it would have paid off; I'm instead trying to reverse-engineer what must be wrong here.

I take it Kokkos calls Kokkos::nearbyint() explicitly (so we can't change the call to a wrapper in our own namespace), in some function we can't reimplement to avoid the call, and Kokkos doesn't implement nearbyint() for one backend ... but isn't that missing implementation a bug report we should file or a PR we could submit there? As is, if we merge this PR and they do fix that backend, then won't we no longer be able to compile against the result, because the compiler will see two definitions?

They state in the code not available as of current SYCL 2020 specification (revision 11). Also explicitly mentioned in their documentation that it is not available in SYCL

[NamjaeChoi]

Opened roystgnr#90.

[NamjaeChoi]

Also it looks like rint and nearbyint are not distinguishable on GPUs due to the lack of standard floating point exceptions. So I guess nearbyint can simply invoke rint.

[NamjaeChoi]

Does the change look reasonable?

[NamjaeChoi]

rint is available from Kokkos 5.1, so we should hold it