On optimal temporal locality of stencil codes

  • Authors:
  • Claudia Leopold

  • Affiliations:
  • Friedrich-Schiller-Universität Jena, Institut für Informatik, 07740 Jena, Germany

  • Venue:
  • Proceedings of the 2002 ACM symposium on Applied computing
  • Year:
  • 2002

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Abstract

Iterative solvers such as the Jacobi and Gauss-Seidel relaxation methods are important, but time-consuming building blocks of many scientific and engineering applications. The performance problems are largely due to cache misses, and can be reduced by tiling the codes. Whereas previous research has shown the usefulness of tiling by experimentally comparing the run times of tiled and original codes, it did not tackle the question as to whether further improvements are possible. In this paper, we give a negative answer, regarding the exploitation of temporal locality in one step of a 2-dimensional stencil code. We derive upper and lower bounds that match up to a factor of about 1 + 2/M, where M is the cache size. For the upper bounds, we investigate some modifications of tiling.