Orchard: Heterogeneous Parallelism and Fine-grained Fusion for Complex Tree Traversals

Abstract

Many applications are designed to perform traversals on tree-like data structures. Fusing and parallelizing these traversals enhance the performance of applications. Fusing multiple traversals improves the locality of the application. The runtime of an application can be significantly reduced by extracting parallelism and utilizing multi-threading. Prior frameworks have tried to fuse and parallelize tree traversals using coarse-grained approaches, leading to missed fine-grained opportunities for improving performance. Other frameworks have successfully supported fine-grained fusion on heterogeneous tree types but fall short regarding parallelization. We introduce a new framework Orchard built on top of Grafter. Orchard’s novelty lies in allowing the programmer to transform tree traversal applications by automatically applying fine-grained fusion and extracting heterogeneous parallelism.Orchard allows the programmer to write general tree traversal applications in a simple and elegant embedded Domain-Specific Language (eDSL). We show that the combination of fine-grained fusion and heterogeneous parallelism performs better than each alone when the conditions are met.