High-Performance Location-Aware Publish-Subscribe on GPUs

Adding location-awareness to publish-subscribe middleware infrastructures would open-up new opportunities to use this technology in the hot area of mobile applications. On the other hand, this requires to radically change the way published events are matched against received subscriptions. In this paper we examine this issue in detail and we present CLCB, a new algorithm using CUDA GPUs for massively parallel, high-performance, location-aware publish-subscribe matching and its implementation into a matching component that allows to easily build a full-edged middleware system. A comparison with the state-of-the-art in this area shows the impressive increment in performance that GPUs may enable, even in this domain. At the same time, our performance analysis allows to identify those peculiar aspects of GPU programming that mostly impact the performance of this kind of algorithm

THREE TEMPORAL PERSPECTIVES ON DECENTRALIZED LOCATION-AWARE COMPUTING: PAST, PRESENT, FUTURE

Durant les quatre dernières décennies, la miniaturisation a permis la diffusion à large échelle des ordinateurs, les rendant omniprésents. Aujourd’hui, le nombre d’objets connectés à Internet ne cesse de croitre et cette tendance n’a pas l’air de ralentir. Ces objets, qui peuvent être des téléphones mobiles, des véhicules ou des senseurs, génèrent de très grands volumes de données qui sont presque toujours associés à un contexte spatiotemporel. Le volume de ces données est souvent si grand que leur traitement requiert la création de système distribués qui impliquent la coopération de plusieurs ordinateurs. La capacité de traiter ces données revêt une importance sociétale. Par exemple: les données collectées lors de trajets en voiture permettent aujourd’hui d’éviter les em-bouteillages ou de partager son véhicule. Un autre exemple: dans un avenir proche, les données collectées à l’aide de gyroscopes capables de détecter les trous dans la chaussée permettront de mieux planifier les interventions de maintenance à effectuer sur le réseau routier. Les domaines d’applications sont par conséquent nombreux, de même que les problèmes qui y sont associés. Les articles qui composent cette thèse traitent de systèmes qui partagent deux caractéristiques clés: un contexte spatiotemporel et une architecture décentralisée. De plus, les systèmes décrits dans ces articles s’articulent autours de trois axes temporels: le présent, le passé, et le futur. Les systèmes axés sur le présent permettent à un très grand nombre d’objets connectés de communiquer en fonction d’un contexte spatial avec des temps de réponses proche du temps réel. Nos contributions dans ce domaine permettent à ce type de système décentralisé de s’adapter au volume de donnée à traiter en s’étendant sur du matériel bon marché. Les systèmes axés sur le passé ont pour but de faciliter l’accès a de très grands volumes données spatiotemporelles collectées par des objets connectés. En d’autres termes, il s’agit d’indexer des trajectoires et d’exploiter ces indexes. Nos contributions dans ce domaine permettent de traiter des jeux de trajectoires particulièrement denses, ce qui n’avait pas été fait auparavant. Enfin, les systèmes axés sur le futur utilisent les trajectoires passées pour prédire les trajectoires que des objets connectés suivront dans l’avenir. Nos contributions permettent de prédire les trajectoires suivies par des objets connectés avec une granularité jusque là inégalée. Bien qu’impliquant des domaines différents, ces contributions s’articulent autour de dénominateurs communs des systèmes sous-jacents, ouvrant la possibilité de pouvoir traiter ces problèmes avec plus de généricité dans un avenir proche. -- During the past four decades, due to miniaturization computing devices have become ubiquitous and pervasive. Today, the number of objects connected to the Internet is in- creasing at a rapid pace and this trend does not seem to be slowing down. These objects, which can be smartphones, vehicles, or any kind of sensors, generate large amounts of data that are almost always associated with a spatio-temporal context. The amount of this data is often so large that their processing requires the creation of a distributed system, which involves the cooperation of several computers. The ability to process these data is important for society. For example: the data collected during car journeys already makes it possible to avoid traffic jams or to know about the need to organize a carpool. Another example: in the near future, the maintenance interventions to be carried out on the road network will be planned with data collected using gyroscopes that detect potholes. The application domains are therefore numerous, as are the prob- lems associated with them. The articles that make up this thesis deal with systems that share two key characteristics: a spatio-temporal context and a decentralized architec- ture. In addition, the systems described in these articles revolve around three temporal perspectives: the present, the past, and the future. Systems associated with the present perspective enable a very large number of connected objects to communicate in near real-time, according to a spatial context. Our contributions in this area enable this type of decentralized system to be scaled-out on commodity hardware, i.e., to adapt as the volume of data that arrives in the system increases. Systems associated with the past perspective, often referred to as trajectory indexes, are intended for the access to the large volume of spatio-temporal data collected by connected objects. Our contributions in this area makes it possible to handle particularly dense trajectory datasets, a problem that has not been addressed previously. Finally, systems associated with the future per- spective rely on past trajectories to predict the trajectories that the connected objects will follow. Our contributions predict the trajectories followed by connected objects with a previously unmet granularity. Although involving different domains, these con- tributions are structured around the common denominators of the underlying systems, which opens the possibility of being able to deal with these problems more generically in the near future

interActors: A Model for Supporting Complex Communication in Concurrent Systems

In concurrent systems, such as multi-core computers, parallel systems, cloud computing systems, and systems involving mobile devices, processes interact with each other. Protocols for interactions among processes are increasingly complex and diverse, which is in part responsible for making programming of concurrent systems difficult. Particularly, in a concurrent program, the code for communication protocols often intermixes with the code for its functional behaviors, compromising modularity and reusability. There is a growing body of work on separating communication concerns of processes from their functional concerns. Although they achieve some degree of separation, they have some disadvantages. For example, the number of communication participants is fixed in some approaches, or in other approaches, communication mechanisms, such as for establishing the initial rendezvous for communication participants is left to the processes. In other words, existing approaches either offer static protocols that cannot handle dynamically evolving number of participants in interactions, or offer complex initialization steps that are left mixed with functional concerns. I propose interActors, a model for supporting complex communications in concurrent systems. I treat a communication as a first-class object which consists of outlets, through which processes can connect to it, and handlers, which are responsible for handling communication logics. Outlets establish a boundary between communications and processes in an application. New outlets can be created if necessary, to handle dynamically changed communication patterns at run-time. We say communications are self-driven because they have outlets and handlers that are active and therefore they can move interactions forward. More complex communications can be constructed by composing simpler communications. Operational semantics and compositional semantics are developed by extending the Actor model of concurrency with support for complex communication. A prototype implementation is developed using Scala and Akka actor library. With the intention of restricting arbitrarily complex code in communications, I developed Communication Specification Language (CSL), which excludes loops from communications and only allows a small set of statements and expressions. interActors are evaluated using case studies and comparison with Reo, a leading coordination model and language. The evaluation shows that interActors offer advantages in terms of programmability, reusability, and modularity