J.L.: Self-consistent MPIIO performance requirements and expectations

Abstract. We recently introduced the idea of self-consistent perfor-mance requirements for MPI communication. Such requirements provide a means to ensure consistent behavior of an MPI library, thereby ensur-ing a degree of performance portability by making it unnecessary for a user to perform implementation-dependent optimizations by hand. For the collective operations in particular, a large number of such rules could sensibly be formulated, without making hidden assumptions about the underlying communication system or otherwise constraining the MPI im-plementation. In this paper, we extend this idea to the realm of parallel I/O (MPI-IO), where the issues are far more subtle. In particular, it is not always possible to specify performance requirements without making assumptions about the implementation or without a priori knowledge of the I/O access pattern. For such cases, we introduce the notion of performance expectations, which specify the desired behavior for good implementations of MPI-IO. I/O performance requirements as well as expectations could be automatically checked by an appropriate bench-marking tool.