Scalability Tuning of the Load Balancing and Coupling Framework FD 4

In this paper, we discuss the scalability tuning of the HPC software framework FD4. The framework provides dynamic load balancing and model coupling for multiphase and multiphysics simulations. We first investigate scalability bottlenecks using the Vampir performance analysis tool-set on the BlueGene/Q system at JSC. Then, we describe and evaluate our optimized algorithms: A new hierarchical 1D partitioning algorithm for SFC-based dynamic load balancing and a new method to organize the coupling metadata. The final scalability benchmark shows that the overhead of FD4 has been reduced by a factor of 3.3 at 262 144 ranks, which leads to a considerably increased scalability of the whole application.

[1]  M. Simmel,et al.  Condensation and activation in sectional cloud microphysical models , 2006 .

[2]  Lawrence Buja,et al.  The computational future for climate and Earth system models: on the path to petaflop and beyond , 2009, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[3]  Jay Walter Larson,et al.  The Model Coupling Toolkit: A New Fortran90 Toolkit for Building Multiphysics Parallel Coupled Models , 2005, Int. J. High Perform. Comput. Appl..

[4]  Matthias Lieber.  Dynamische Lastbalancierung und Modellkopplung zur hochskalierbaren Simulation von Wolkenprozessen , 2012 .

[5]  Cevdet Aykanat,et al.  Fast optimal load balancing algorithms for 1D partitioning , 2004, J. Parallel Distributed Comput..

[6]  Karen Dragon Devine,et al.  Partitioning and Dynamic Load Balancing for the Numerical Solution of Partial Differential Equations , 2006 .

[7]  Serge Miguet,et al.  Heuristics for 1D Rectilinear Partitioning as a Low Cost and High Quality Answer to Dynamic Load Balancing , 1997, HPCN Europe.

[8]  John Shalf,et al.  The International Exascale Software Project roadmap , 2011, Int. J. High Perform. Comput. Appl..

[9]  Matthias S. Müller,et al.  Highly Scalable Dynamic Load Balancing in the Atmospheric Modeling System COSMO-SPECS+FD4 , 2010, PARA.

[10]  V. Grützun,et al.  Simulation of the influence of aerosol particle characteristics on clouds and precipitation with LM-SPECS: Model description and first results , 2008 .

[11]  Matthias S. Müller,et al.  The Vampir Performance Analysis Tool-Set , 2008, Parallel Tools Workshop.