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THEMIS: Component dependence metadata in adaptive parallel computations

Paul Kelly, Olav Beckmann, A. J. Field, Scott Baden

Journal Article
Parallel Processing Letters
Volume 11
Issue 4
December, 2001
World Scientific
ISSN 0129-6264
DOI 10.1142/S0129626401000725

There is a conflict between the goals of improving the quality of scientific software and improving its performance. A key issue is to support reuse and re-assembly of sophisticated software components without compromising performance. This paper describes THEMIS, a programming model and run time library being designed to support cross-component performance optimisation through explicit manipulation of the computation's iteration space at run-time.

Each component is augmented with "component dependence metadata", which characterises the constraints on its execution order, data distribution and memory access order. We show how this supports dynamic adaptation of each component to exploit the available resources, the context in which its operands are generated, and results are used, and the evolution of the problem instance.

Using a computational fluid dynamics visualisation example as motivation, we show how component dependence metadata provides a framework in which a number of interesting optimisations become possible. Examples include data placement optimisation, loop fusion, tiling, memoisation, checkpointing and incrementalisation.

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