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Colloquium - Levesque

PGAS for Large Scale Parallel Computing
John Levesque
Cray Supercomputer Center of Excellence

This talk will cover the advantages of using PGAS with MPI going forward in the realm of utilizing many 100,000 of processors. While MPI has served the HPC community extremely well it is having difficulty handling the number of messages that occur when complex applications are running on 100,000s of processors. The main difficulty is the message matching required by MPI. This processing is needed when point to point messages are being used to overlap computation and communication. Message matching is not required when using a PGAS language like Co-Array Fortran and UPC. These languages allow the programmer to "fire and forget" communications and easily overlap communication with other communication and with computation. A tremendous advantage of these language extensions are that they can incrementally be used to replace ineffective MPI. The talk will concentrate on Co-Array Fortran and in particular in the subset of CAF that has been proposed for incorporating into the latest 2008 standard. Comparisons and examples will be shown to illustrate the points.

John Levesque is the director of the Cray Supercomputing Center of Excellence at the Department of Energy's Oak Ridge National Laboratory (ORNL), the world's most powerful supercomputer for open (non-classified) scientific research. Levesque leads a team of engineers providing application and high performance computing expertise to researchers using ORNL systems. The Center of Excellence offers scientists and engineers from around the globe access to deep HPC application performance knowledge, allowing them to focus on their science or engineering challenge. Levesque also works closely with ORNL staff members to optimize application performance on ORNL's XT supercomputers.

From 2001 to 2003, Levesque was a senior principal engineer responsible for the benchmarking initiatives for the Cray XI system, playing a key role in helping CINECA, Italy's national supercomputer center and the Department of Defense Modernization Program optimize their applications. Prior to Cray, Levesque was the director of the Advanced Computer Technology Center at IBM's Watson Research Center where his team received the Scientific Achievement Award for contributing more than $200 million in new business sales in 2000.

With more than 35 years experience in high performance computing, Levesque is a recognized expert in the optimization of FORTRAN programs and parallel vector system architectures. He has been involved in the Advanced Strategic Computing Initiative at the US Department of Energy, the National Academy of Sciences, and is a regular contributor to the Cray User Conference. Levesque has also contributed to numerous publications on the optimization of programs for advanced scientific computers including a collection of papers entitled "Concurrency and Computations" in 2003 and a book entitled Guidebook to FORTRAN on Supercomputers published in 1989. Levesque has a Bachelor of Arts and Master of Arts in Mathematics from the University of New Mexico in Albuquerque, New Mexico.

This talk is sponsored by the National Center for Atmospheric Research Computational & Information Systems Laboratory and will be held in the Main Seminar Room at the Mesa Lab.

Department of Computer Science
University of Colorado Boulder
Boulder, CO 80309-0430 USA
May 5, 2012 (14:13)