Bert Wesarg

I see two instances of invalidating the `contiguous.max_type`: [here](https://github.com/dash-project/dash/blob/22f6487c4ea2a86c9d6e223892048a7dd6042a5b/dart-impl/mpi/src/dart_mpi_types.c#L361) `MPI_DATATYPE_NULL` is used. But [here](https://github.com/dash-project/dash/blob/22f6487c4ea2a86c9d6e223892048a7dd6042a5b/dart-impl/mpi/src/dart_mpi_types.c#L346) and [here](https://github.com/dash-project/dash/blob/22f6487c4ea2a86c9d6e223892048a7dd6042a5b/dart-impl/mpi/src/dart_mpi_types.c#L315) `DART_MPI_TYPE_UNDEFINED` is used. This seems erroneous, as `max_type` is of type `MPI_Datatype`. Though, I...

While I do not think this will fix it, but here is some cleanup and a check before calling `MPI_Type_free` ```diff diff --git i/dart-impl/mpi/include/dash/dart/mpi/dart_communication_priv.h w/dart-impl/mpi/include/dash/dart/mpi/dart_communication_priv.h index d146865c9..1a66ea3f4 100644 dart-impl/mpi/include/dash/dart/mpi/dart_communication_priv.h ---...

Sure, do you think it fixes anything related to my problem here?

> Actually, the last two lines of the patch might be the culprit (https://github.com/dash-project/dash/pull/709/files#diff-f99e41ced414d50f5b467c4e54685f19R360). But this should be `!= MPI_DATATYPE_NULL` for all basic types, thus it should not matter.

I will push the changes to SPEC and ask kindly if this is fixed on HPE Cray

Only the declaration is missing, i.e., it does not show up in any header.

I would not consider the `build*.sh` scripts a good place to document CMake variables. why not inside `CMakeLists.txt` into the `options()`? Btw, does other combinations instead of `off`&`off` or `on`&`on`...

Somehow, we need to keep the `domain_tag` init to `"."`, even though `dart__base__locality__domain__create_subdomains` does this for us. If not, I get this runtime error: ``` [ 0 ERROR ] [...

@pascalj this is needed to get the executor in mephisto work again: https://github.com/mephisto-hpc/testing/commit/60f6084ca9791169eadfe3f5ddf72d7694cc021c#diff-0d729d073571dd4e46129f851327de2eR39

> As a workaround for now, we could introduce `dash::global_iterator_traits::memory_type`, default-defined as `void` and specialized for ("befriended") global iterators which are actually memory-bound. Ok, but than why did you removed...