Phil’s Promised Presentation on POP’s Present Progress, Performance and Penultimate Post-present Plan POP People P. Malone, P. Smith, P. Maltrud, P. Jones, P. Davis, P. Baumgardner, P. Dukowicz

Past/Present Bryan-Cox-Semtner z-coordinate Introduced features like free surface, pressure-averaging, implicit surface pressure formulation, etc. General grids (dipole, tripole, icos) Added (and improved) GM, KPP, anisotropic viscosity, variable sfc layer, partial bottom cells, new EOS and time manager Publicly available (version 1.4.3)

POP Purpose High Resolution Simulations –Global 0.28, 0.1 (Bert) –North Atlantic 0.4, 0.2, 0.1, 1/15 –Wind-driven circulation, eddy processes, performance Coupled Simulations (CCPP) –NCAR CCSM/PCM (Peter), CSU, UCLA, CICE –Long times, parameterizations, performance, inter-model Homeland Security

POP 2.0 Gates release Partial bottom cells New EOS Tripole grids Performance –Hybrid OpenMP/MPI –Better cache performance –Land point elimination

POP 2.0  Sub-block decomposition Domain decomposed into blocks sized for cache (or vector) Land blocks eliminated Remaining blocks distributed in load-balanced manner using a rake algorithm Priorities can be set to maintain some locality during rake Many blocks on each node provide OpenMP parallelism Block loops at high level to amortize OpenMP overhead Different block distribution used for barotropic solver to optimize for communication rather than load balance

Actual Performance 0.1 Global oldnew Total115s55s Baroclinic93s38s Barotropic9s7s

POP x1 Performance MLP?

Future Improvements Hybrid Vertical Coordinate (ALE) –Lagrangian vertical coordinate –Remap (infrequently) to arbitrary coordinate New incremental remapping advection –Conservative, monotone scheme –Inexpensive for many tracers Explicit barotropic split Two-time-level (no mixing, smaller restart)

Future Improvements (cont.) New Tracer Structure for Biogeochemistry (NOPP, SciDAC, CCSM) Icosahedral Grid (SciDAC CSU) CCSM SciDAC SciDAC ISICS (grids, performance, CCA) ESMF Compliant

Interactions POP CICE SCRIP NPS NCAR CCSM CSU UCLA LLNL ORNL ANL LANL NOPP SciDAC ESMF PRISM CCPP