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W. Gropp, T. Hoefler, R. Thakur, J. Träff:
"Performance Expectations and Guidelines for MPI Derived Datatypes";
Vortrag: EuroMPI 2011, Santorini, Greece; 18.09.2011 - 21.09.2011.

MPI´s derived datatypes provide a powerful mechanism for concisely describing arbitrary, noncontiguous layouts of user data for use in MPI communication. This paper formulates self-consistent performance guidelines for derived datatypes. Such guidelines make performance
expectations for derived datatypes explicit and suggest relevant
optimizations to MPI implementers. We also identify self-consistent
guidelines that are too strict to enforce, because they entail NP-hard optimization problems. Enforced self-consistent guidelines assure the user that certain manual datatype optimizations cannot lead to performance improvements, which in turn contributes to performance portability between MPI implementations that behave in accordance with the guidelines. We present results of tests with several MPI implementations, which indicate that many of them violate the guidelines.