Tools Using the New MPI Tools Information Interface (MPI_T)
MPI_T is an interface for tools introduced in the 3.0 version of MPI. The interface provides mechanisms for tools to access and set performance and control variables that are exposed by an MPI implementation. For example, a tool may be able to record the length of the unexpected message queue over the course of the execution; or a tool could set the value of the “eager limit” for better message passing performance. The number and types of variables that are exposed are completely determined by the MPI implementation and need to be discovered by tools via the query interface. Thus, tool writers need to take care to code in such a way that they are not dependent on a single implementation’s variables. The latest versions of major MPI implementations, including Open MPI, MPICH and MVAPICH, are already providing MPI_T functionality, making it widely accessible to users.