Performance analysis and tuning of the XNS CFD solver on Blue Gene/L

  • Authors:

  • Brian J. N. Wylie;Markus Geimer;Mike Nicolai;Markus Probst

  • Affiliations:

  • John von Neumann Institute for Computing, Forschungszentrum Jülich GmbH, Jülich, Germany;John von Neumann Institute for Computing, Forschungszentrum Jülich GmbH, Jülich, Germany;Computational Analysis of Technical Systems, Centre for Computational Engineering Science, RWTH Aachen University, Aachen, Germany;Computational Analysis of Technical Systems, Centre for Computational Engineering Science, RWTH Aachen University, Aachen, Germany

  • Venue:
  • PVM/MPI'07 Proceedings of the 14th European conference on Recent Advances in Parallel Virtual Machine and Message Passing Interface
  • Year:
  • 2007

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Abstract

The xns computational fluid dynamics code was successfully running on Blue Gene/L, however, its scalability was unsatisfactory until the first Jülich BlueGene/L Scaling Workshop provided an opportunity for the application developers and performance analysts to start working together. Investigation of solver performance pin-pointed a communication bottleneck that appeared with approximately 900 processes, and subsequent remediation allowed the application to continue scaling with a four-fold simulation performance improvement at 4,096 processes. This experience also validated the scalasca performance analysis toolset, when working with a complex application at large scale, and helped direct the development of more comprehensive analyses. Performance properties have now been incorporated to automatically quantify point-to-point synchronisation time and wait states in scan operations, both of which were significant for xns on BlueGene/L.