Per MPI 3.1 chapter 13.3 :
"Derived etypes can be constructed by using any of the MPI
datatype constructor routines, provided all resulting typemap
displacements are non-negative and monotonically nondecreasing."
Same restriction applies to ftypes.
add the OMPI_DATATYPE_CHECK_FOR_VIEW() macro that is
check the underlying opal_datatype_t is monotonic, on top
of all checks performed in OMPI_DATATYPE_CHECK_FOR_RECV().
Since checking monotoniciy is expensive, check is only performed
when needed, but the result is cached by ompi_datatype_is_monotonic().
Thanks Wei-keng Liao for the valuable feedback.
Thanks George for the guidance.
Refs. open-mpi/ompi#4682
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
02f8215b25