Exploring the Capabilities of the New MPI_T Interface

The latest version of the MPI Standard, MPI 3.0, includes a new interface for tools, the MPI Tools Information Interface (MPI_T). In this paper, we focus on the new functionality and insights that users can gain from MPI_T. For this purpose, we present two new tools that are the first that exploit the new interface. Varlist allows users to query and document the MPI environment and Gyan provides profiling information using internal MPI performance variables. Together, these tools provide users with new capabilities in a highly portable way that previously required in-depth knowledge of individual MPI implementations, and demonstrate the advantages of MPI_T. In our case studies, we demonstrate how MPI_T enables both MPI library and application developers to study the impact of an MPI library's runtime settings and implementation specific behaviors on the performance of applications.