Fast algorithms for compressed multimethod dispatch table generation

Abstract

The efficiency of dynamic dispatch is a major impediment to the adoption of multimethods in object-oriented languages. In this article, we propose a simple multimethod dispatch scheme based on compressed dispatch tables. This scheme is applicable to any object-oriented language using a method precedence order that satisfies a specific monotonous property (e.g., as Cecil and Dylan) and guarantees that dynamic dispatch is performed in constant time, the latter being a major requirement for some languages and applications. We provide efficient algorithms to build the dispatch tables, provide their worst-case complexity, and demonstrate the effectiveness of our scheme by real measurements performed on two large object-oriented applications. Finally, we provide a detailed comparison of our technique with other existing techniques.