View: HostMirror and host_mirror_type aliases seem redundant (which one do we kill?)

[romintomasetti]

Summary

The alias host_mirror_type defined in

kokkos/core/src/Kokkos_View.hpp

Lines 657 to 660 in e4cc686

	using host_mirror_type =
	View<typename traits::non_const_data_type, typename traits::array_layout,
	typename traits::host_mirror_space, typename traits::hooks_policy>;

seems redundant with HostMirror

kokkos/core/src/Kokkos_View.hpp

Lines 650 to 655 in e4cc686

	using HostMirror =
	View<typename traits::non_const_data_type, typename traits::array_layout,
	Device<DefaultHostExecutionSpace,
	typename traits::host_mirror_space::memory_space>,
	typename traits::hooks_policy>;

The main difference is that one is using the host_mirror_space, the other creates a Kokkos::Device.

Which alias should we deprecate ?

Investigations

The alias host_mirror_type is used 2 times in Kokkos and 9 times in Trilinos. It is not mentioned in the documentation, but HostMirror is (https://kokkos.org/kokkos-core-wiki/API/core/view/view.html#_CPPv410HostMirror).

Suggestion

Deprecate host_mirror_type, see who complains.

[dalg24]

HostMirror is the only one mentioned in the doc and it is all over our teaching material so it is clear if we cannot get rid of it.
We could attempt to deprecate the host_mirror_type member as you suggest. I don't feel too strongly about it.