Within this paper, we present the functionality of an extended MPI library for verifying correct use and consistency of all collective functions of the MPI-2 standard. The library is part of the MPI/SX implementation for the NEC SX-series of parallel vector-computers, as well as NEC implementations of MPI for other platforms.
We give examples of the use of the verification library, and in particular report on the overheads entailed for synthetic benchmarks and applications. The library could have been implemented as a stand-alone, portable interface by using the MPI profiling interface as defined by the MPI standard. We discuss obstacles of a portable implementation, and instead argue to support collective verification as part of any good MPI implementation.