© 2008 Pittsburgh Supercomputing Center Proposed ideas for consideration under AUS

© 2008 Pittsburgh Supercomputing Center Revisit Mixed MPI-OpenMP Programming model? Is it time to revive mixed MPI-OpenMP programming model? –People have been looking at it for a while –Not very successful so far –Not enough cores/processor to justify –Not enough processors/node to justify –Halfhearted attempts? Have things changed? –8-16 cores per node in current T2 systems –Are we at the tipping point? Or, where is the tipping point?

© 2008 Pittsburgh Supercomputing Center Hybrid OpenMP-MPI Benchmark Simple benchmark code Permits systematic evaluation –Vary compute-comm ratio –Vary comm message sizes –Vary MPI – OpenMP balance Should we expect better performance? Is this a worthwhile approach for real applications? Hopefully provides some limits in the idealized case

© 2008 Pittsburgh Supercomputing Center Real application with Mixed MPI-OpenMP WRF ENZO POPS Other user codes?

© 2008 Pittsburgh Supercomputing Center FFT benchmarks on T2 systems Not the HPCC one More realistic dimensions 256^3 to 4086^3 –2D processor decomposition already implemented (PK’s code) –How would this compare with a slab decomposition with Mixed MPI-OpenMP? Does one exist? Also can result in tuning suggestions for users

© 2008 Pittsburgh Supercomputing Center Hybrid Architectures (Hardware) Emerging architecture There is a lot to be learned Benchmark existing applications? –NAMD –WRF

© 2008 Pittsburgh Supercomputing Center IO Benchmarking? Experiment with models actually used by users Create "Best Practices“ for IO?