Dispatch multiple | EPFL Graph Search

Le dispatch multiple est une fonctionnalité de certains langages orientés objet ou fonctionnels dans lesquels une fonction ou une méthode peut être spécialisée pour plus d'un de ses paramètres formels. On l'appelle alors multiméthode. La spécialisation d'une multiméthode peut ainsi dépendre du type dynamique de plusieurs de ses paramètres objets, à la différence des langages de programmation orientés objet classiques, dans lesquels la spécialisation ne dépend que du premier paramètre implicite this. Elle se distingue de la surcharge de fonction présente dans de nombreux langages de programmation, dans lesquels le choix de la fonction à utiliser dépend du type statique de ses paramètres, ce qui correspond à un dispatch multiple effectué au moment de la compilation. Le premier environnement orienté objet à avoir eu cette fonctionnalité, et le plus connu, est le Common Lisp Object System, mais d'autres langages comme Dylan, Slate, Cecil, GNU Guile, Seed7, Julia et le descendant de Jav

Just-in-time performance without warm-up

Denys Shabalin

Scala has been developed as a language that deeply integrates with the Java ecosystem. It offers seamless interoperability with existing Java libraries. Since the Scala compiler targets Java bytecode, Scala programs have access to high-performance runtimes including the HotSpot virtual machine. HotSpot provides impressive performance results achieved via just-in-time compilation. It starts program execution in interpreter mode, collecting profile feedback about called methods. This information allows HotSpot to identify hot spots in the program, which are then compiled on the fly to native code. This compilation scheme enables high peak performance at the cost of warmup time required to collect the profile data and perform just-in-time compilation. This is a good example of the traditional tradeoff between ahead-of-time (AOT) and just-in-time (JIT) compilation. With AOT, compilers have less information, but the runtime story is reasonably straightforward. With JIT, compilers have more information, which enables advanced optimizations, but the runtime story becomes complicated. In this dissertation, we present the design and implementation of Scala Native, an optimizing compiler for Scala. With Scala Native, Scala programs are compiled ahead of time, which avoids runtime compilation and enables instant startup times. On the other hand, Scala Native is able to match and supersede the peak performance of HotSpot on our benchmarks. In addition to that, Scala Native is a general-purpose Scala compiler - programs compiled by Scala Native closely match the behavior of programs compiled by the Scala compiler. First, we introduce NIR, an intermediate representation designed with ahead-of-time compilation in mind. NIR represents programs in the single-static assignment form and has support for object-oriented features such as virtual dispatch and multiple inheritance. This representation is a key enabler of our compilation and optimization pipeline. Secondly, we present Interflow, a link-time optimizer that takes advantage of the closed-world assumption to optimize the whole program at once. Our optimizer employs a number of techniques including partial evaluation, allocation sinking, and method duplication. The combination of these techniques allows Scala Native to outperform HotSpot on the majority of our benchmarks. Finally, we describe how to improve runtime performance even further based on profile feedback. We propose a technique that splits methods apart isolating key hot paths that are then optimized more aggressively than the cold parts of the program. This provides a further performance advantage over HotSpot.

EPFL2020

Towards better entity resolution techniques for Web document collections

Karl Aberer, Zoltán Miklós, Surender Reddy Yerva

As person names are non-unique, the same name on different Web pages might or might not refer to the same real-world person. This entity identification problem is one of the most challenging issues in realizing the Semantic Web or entity-oriented search. We address this disambiguation problem, which is very similar to the entity resolution problem studied in relational databases, however there are also several differences. Most importantly Web pages often only contain partial or incomplete information about the persons, moreover the available information is very heterogeneous, thus we are only able to obtain some uncertain evidence about whether two names refer to the same person using similarity functions. These similarity functions capture some aspects of the similarities between Web-pages, where the names occur, thus they perform very differently for the different names. We analyze some data engineering techniques to cope with the limited accuracy of the similarity functions and to combine multiple functions. Even with our simple techniques we could demonstrate systematic performance improvements and produce comparable results to state-of-the-art methods.

1st International Workshop on Data Engineering meets the Semantic Web (DESWeb'2010) (co-located with ICDE'2010)2010

Towards better entity resolution techniques for Web document collections

Karl Aberer, Zoltán Miklós, Surender Reddy Yerva

IEEE2010

Just-in-time performance without warm-up

Denys Shabalin

EPFL2020