BatchedTeamGemv fails with ViewType = Kokkos::DynRankView<>

[japlews]

BatchedTeamGemv is now incompatible with Kokkos::DynRankView<> because of static assertions on View rank. See KokkosBatched_Gemv_Team_Impl.hpp:48:

    static_assert(AViewType::Rank == 3,
                  "Batched TeamGemv requires rank-3 A matrix (use "
                  "KokkosBlas::TeamGemv for regular rank-2 matrix)");

I can work around this issue by using the Batched_Gemm interface instead (which does not require compile-time View dimensions for some reason), but I'm wondering if there are plans to continue support for DynRankView?

Thanks!
Julia

[kliegeois]

@lucbv do you have an opinion about this support? I don't have experience with DynRankView.

[e10harvey]

@japlews: While the functor-level interfaces (https://kokkos-kernels.readthedocs.io/en/latest/developer/apidocs/batched_dense.html#gemm) do not check the compile-time View dimensions, our host-level BatchedGemm function does:
/// \brief Non-blocking solve of general matrix multiply on a batch of

[japlews]

Thanks for the information. Would it be possible to support an API with conditional compile- and run-time checks based on the existence of a compile-time View rank? The Trilinos/Intrepid2 library is the use case in question here, where the API-level array types they rely on are almost all Kokkos::DynRankViews... Or otherwise something more complex that is duck-typed like a Kokkos::DynRankView.

[e10harvey]

@japlews: For this use-case, Rank in ViewType::Rank would not exist? If so, I think this can be supported via sizeof and SFINAE.

[japlews]

@e10harvey, exactly. DynRankViews have a method called ViewType::rank() rather than a ViewType::Rank based on template parameters. It seems in principle like this would be tractable using constexpr if rather than SFINAE. See, for example, the free functions defined at https://github.com/kokkos/kokkos/blob/aa1f48f3172069f212ed2c97b74b786999b26f17/core/src/Kokkos_View.hpp#L1690 and https://github.com/kokkos/kokkos/blob/aa1f48f3172069f212ed2c97b74b786999b26f17/containers/src/Kokkos_DynRankView.hpp#L1302

[lucbv]

I am thinking something like this:

if constexpr (Kokkos::is_dyn_rank_view<user_type>::value) {
   // runtime check of view.rank();
} else {
   static_assert(user_type::rank == 3)
}

[e10harvey]

Nice!

[e10harvey]

@japlews: A fix for this was propsed via #1850 last week, can you please check if that fix resolves this issue?

[japlews]

@e10harvey, I was able to confirm that my code builds and runs with the fixes. Thanks!

[e10harvey]

Closing as complete.