Kokkos lacks "global" is_initialized

[mhoemmen]

Kokkos' execution spaces have an is_initialized method, but there is no "global" Kokkos::is_initialized. This makes it hard to prevent double initialization or finalization. This matters because Kokkos::initialize sets up state that is independent of execution spaces, e.g., the Kokkos profiling library.

[ibaned]

I believe @dsunder has committed or soon-to-be-committed changes along these lines, including idempotent initialize/finalize. I think we're also moving to have users just call Kokkos::initialize and not the individual spaces, so Kokkos::is_initialized makes sense to me.

[hcedwar]

Resolve interaction with global initialize vs. to-be-deprecated individual device initialize functions

[mhoemmen]

poke

[ibaned]

@dsunder the world eagerly awaits your many improvements. no pressure though :)

[mhoemmen]

This issue, and the fact that Kokkos::Serial is always initialized, may be causing memory leaks in Nalu and other apps. This breaks the "initialize Kokkos if it is not already initialized" pattern in Tpetra.

@DrBooom

[ibaned]

As @dsunder commented here, Kokkos::is_initialized is apparently in develop right now and will be available in the next snapshot.