MPI does not specify:
There are many features that were considered and not included in MPI. This happened for a number of reasons: the time constraint that was self-imposed by the MPI Forum in finishing the standard; the feeling that not enough experience was available on some of these topics; and the concern that additional features would delay the appearance of implementations.
Features that are not included can always be offered as extensions
by specific
implementations.
Future versions of MPI will address some of these issues (see
Section 
).