The Choice Construct in the Souffle Language

TL;DR

This paper introduces a choice construct in the Souffle Datalog engine, enabling concise expression of complex algorithms and achieving significant performance improvements in worklist computations.

Contribution

It presents a novel relation-based choice construct for Souffle, enhancing expressiveness and performance for large-scale, non-deterministic algorithms.

Findings

Choice construct enables expressing worklist algorithms in few lines

Algorithms with choice run up to 10,000 times faster

Relation-based choice differs from rule-based choice in prior work

Abstract

Datalog has become a popular implementation language for solving large-scale, real-world problems, including bug finders, network analysis tools, and disassemblers. These applications express complex behaviour with hundreds of relations and rules that often require a non-deterministic choice for tuples in relations to express worklist algorithms. This work is an experience report that describes the implementation of a choice construct in the Datalog engine Souffle. With the choice construct, we can express worklist algorithms such as spanning trees in a few lines of code. We highlight the differences between rule-based choice as described in prior work, and relation-based choice introduced by this work. We show that a choice construct enables certain worklist algorithms to be computed up to 10kx faster than having no choice construct.