Symmetry in software synthesis

Abstract

With the surge of multi- and many-core systems, much research has focused on algorithms for mapping and scheduling on these complex platforms. Large classes of these algorithms face scalability problems. This is why diverse methods are commonly used for reducing the search space. While most such approaches leverage the inherent symmetry of architectures and applications, they do it in a problem-specific and intuitive way. However, intuitive approaches become impractical with growing hardware complexity, like Network-on-Chip interconnect or heterogeneous cores. In this article, we present a formal framework that can determine the inherent local and global symmetry of architectures and applications algorithmically and leverage these for problems in software synthesis. Our approach is based on the mathematical theory of groups and a generalization called inverse semigroups. We evaluate our approach in two state-of-the-art mapping frameworks. Even for the platforms with a handful of cores of today and moderate-sized benchmarks, our approach consistently yields reductions of the overall execution time of algorithms. We obtain a speedup of more than 10× for one use-case and saved 10% of time in another.