Lu-Lu: A framework for collaborative decision making games

This paper proposes Lu-Lu as an add-on architecture to open MMOGs and social network games, which has been developed to utilise a key set of ingredients that underline collaborative decision making games as reported within the research literature: personalisation, team matching, non-optimal decision making, leading, decisiveness index, scoring, levelling, and multiple stages. The implementation of Lu-Lu is demonstrated as an add-on to the classic supply chain beer game, including customisation of Lu-Lu to facilitate information exchange through the Facebook games platform, e.g., Graph API and Scores API. Performance assessment of Lu-Lu using Behaviour-Driven Development suggests a successful integration of all key ingredients within Lu-Lu's architecture, yielding autonomous behaviour that improves both player enjoyment and decision making

Analyzing the effect of tcp and server population on massively multiplayer games

Many Massively Multiplayer Online Role-Playing Games (MMORPGs) use TCP flows for communication between the server and the game clients. The utilization of TCP, which was not initially designed for (soft) real-time services, has many implications for the competing traffic flows. In this paper we present a series of studies which explore the competition between MMORPG and other traffic flows. For that aim, we first extend a source-based traffic model, based on player’s activities during the day, to also incorporate the impact of the number of players sharing a server (server population) on network traffic. Based on real traffic traces, we statistically model the influence of the variation of the server’s player population on the network traffic, depending on the action categories (i.e., types of in-game player behaviour). Using the developed traffic model we prove that while server population only modifies specific action categories, this effect is significant enough to be observed on the overall traffic. We find that TCP Vegas is a good option for competing flows in order not to throttle the MMORPG flows and that TCP SACK is more respectful with game flows than other TCP variants, namely, Tahoe, Reno, and New Reno. Other tests show that MMORPG flows do not significantly reduce their sending window size when competing against UDP flows. Additionally, we study the effect of RTT unfairness between MMORPG flows, showing that it is less important than in the case of network-limited TCP flows

Contributions à la réplication de données dans les systèmes distribués à grande échelle

Data replication is a key mechanism for building a reliable and efficient data management system. Indeed, by keeping several replicas for each piece of data, it is possible to improve durability. Furthermore, well-placed copies reduce data accesstime. However, having multiple copies for a single piece of data creates consistency problems when the data is updated. Over the last years, I made contributions related to these three aspects: data durability, data access performance and data consistency. RelaxDHT and SPLAD enhance data durability by placing data copies smartly. Caju, AREN and POPS reduce access time by improving data locality and by taking popularity into account. To enhance data lookup performance, DONUT creates efficient shortcuts taking data distribution into account. Finally, in the replicated database context, Gargamel parallelizes independent transactions only, improving database performance and avoiding aborting transactions. My research has been carried out in collaboration with height PhD students, four of which have defended. In my future work, I plan to extend these contributions by (i) designing a storage system tailored for MMOGs, which are very demanding, and (ii) designing a data management system that is able to re-distribute data automatically in order to scale the number of servers up and down according to the changing workload, leading to a greener data management.La réplication de données est une technique clé pour permettre aux systèmes de gestion de données distribués à grande échelle d'offrir un stockage fiable et performant. Comme il gère un nombre suffisant de copies de chaque donnée, le système peut améliorer la pérennité. De plus, la présence de copies bien placées réduit les temps d'accès. Cependant, cette même existence de plusieurs copies pose des problèmes de cohérence en cas de modification. Ces dernières années, mes contributions ont porté sur ces trois aspects liés à la réplication de données: la pérennité des données, la performance desaccès et la gestion de la cohérence. RelaxDHT et SPLAD permettent d'améliorer la pérennité des données en jouant sur le placement des copies. Caju, AREN et POPS permettent de réduire les temps d'accès aux données en améliorant la localité et en prenant en compte la popularité. Pour accélérer la localisation des copies, DONUT crée des raccourcis efficaces prenant en compte la distribution des données. Enfin, dans le contexte des bases de données répliquées,Gargamel permet de ne paralléliser que les transactions qui sont indépendantes, améliorant ainsi les performances et évitant tout abandon de transaction pour cause de conflit. Ces travaux ont été réalisés avec huit étudiants en thèse dont quatre ont soutenu. Pour l'avenir, je me propose d'étendre ces travaux, d'une part en concevant un système de gestion de données pour les MMOGs, une classe d'application particulièrement exigeante; et, d'autre part, en concevant des mécanismes de gestion de données permettant de n'utiliser que la quantité strictement nécessaire de ressources, en redistribuant dynamiquement les données en fonction des besoins, un pas vers une gestion plus écologique des données

Analyzing the Effect of TCP and Server Population on Massively Multiplayer Games

Many Massively Multiplayer Online Role-Playing Games (MMORPGs) use TCP flows for communication between the server and the game clients. The utilization of TCP, which was not initially designed for (soft) real-time services, has many implications for the competing traffic flows. In this paper we present a series of studies which explore the competition between MMORPG and other traffic flows. For that aim, we first extend a source-based traffic model, based on player’s activities during the day, to also incorporate the impact of the number of players sharing a server (server population) on network traffic. Based on real traffic traces, we statistically model the influence of the variation of the server’s player population on the network traffic, depending on the action categories (i.e., types of in-game player behaviour). Using the developed traffic model we prove that while server population only modifies specific action categories, this effect is significant enough to be observed on the overall traffic. We find that TCP Vegas is a good option for competing flows in order not to throttle the MMORPG flows and that TCP SACK is more respectful with game flows than other TCP variants, namely, Tahoe, Reno, and New Reno. Other tests show that MMORPG flows do not significantly reduce their sending window size when competing against UDP flows. Additionally, we study the effect of RTT unfairness between MMORPG flows, showing that it is less important than in the case of network-limited TCP flows

A Systematic Mapping Study of MMOG Backend Architectures

The advent of utility computing has revolutionized almost every sector of traditional software development. Especially commercial cloud computing services, pioneered by the likes of Amazon, Google and Microsoft, have provided an unprecedented opportunity for the fast and sustainable development of complex distributed systems. Nevertheless, existing models and tools aim primarily for systems where resource usage—by humans and bots alike—is logically and physically quite disperse resulting in a low likelihood of conflicting resource access. However, a number of resource-intensive applications, such as Massively Multiplayer Online Games (MMOGs) and large-scale simulations introduce a requirement for a very large common state with many actors accessing it simultaneously and thus a high likelihood of conflicting resource access. This paper presents a systematic mapping study of the state-of-the-art in software technology aiming explicitly to support the development of MMOGs, a class of large-scale, resource-intensive software systems.By examining the main focus of a diverse set of related publications, we identify a list of criteria that are important for MMOG development. Then, we categorize the selected studies based on the inferred criteria in order to compare their approach, unveil the challenges faced in each of them and reveal research trends that might be present. Finally we attempt to identify research directions which appear promising for enabling the use of standardized technology for this class of systems

Small Latency Variations Do Not Affect Player Performance in First-Person Shooters

In interactive systems high latency affects user performance and experience. This is especially problematic in video games. A large number of studies on this topic investigated the effects of constant, high latency. However, in practice, latency is never constant but varies by up to 100 ms due to variations in processing time and delays added by polling between system components. In a large majority of studies, these variations in latency are neither controlled for nor reported. Thus, it is unclear to which degree small, continuous variations in latency affect user performance. If these unreported variations had a significant impact, this might cast into doubt the findings of some studies. To investigate how latency variation affects player performance and experience in games, we conducted an experiment with 28 participants playing a first-person shooter. Participants played with two levels of base latency (50 ms vs. 150 ms) and variation (0 ms vs. 50 ms). As expected, high base latency significantly reduces player performance and experience. However, we found strong evidence that small variations in latency in the order of 50 ms, do not affect player performance significantly. Thus, our findings mitigate concerns that previous latency studies might have systematically ignored a confounding effect

Passage à l'échelle pour les mondes virtuels

Virtual worlds attract millions of users and these popular applications --supported by gigantic data centers with myriads of processors-- are routinely accessed. However, surprisingly, virtual worlds are still unable to host simultaneously more than a few hundred users in the same contiguous space.The main contribution of the thesis is Kiwano, a distributed system enabling an unlimited number of avatars to simultaneously evolve and interact in a contiguous virtual space. In Kiwano we employ the Delaunay triangulation to provide each avatar with a constant number of neighbors independently of their density or distribution. The avatar-to-avatar interactions and related computations are then bounded, allowing the system to scale. The load is constantly balanced among Kiwano's nodes which adapt and take in charge sets of avatars according to their geographic proximity. The optimal number of avatars per CPU and the performances of our system have been evaluated simulating tens of thousands of avatars connecting to a Kiwano instance running across several data centers, with results well beyond the current state-of-the-art.We also propose Kwery, a distributed spatial index capable to scale dynamic objects of virtual worlds. Kwery performs efficient reverse geolocation queries on large numbers of moving objects updating their position at arbitrary high frequencies. We use a distributed spatial index on top of a self-adaptive tree structure. Each node of the system hosts and answers queries on a group of objects in a zone, which is the minimal axis-aligned rectangle. They are chosen based on their proximity and the load of the node. Spatial queries are then answered only by the nodes with meaningful zones, that is, where the node's zone intersects the query zone.Kiwano has been successfully implemented for HybridEarth, a mixed reality world, Manycraft, our scalable multiplayer Minecraft map, and discussed for OneSim, a distributed Second Life architecture. By handling avatars separately, we show interoperability between these virtual worlds.With Kiwano and Kwery we provide the first massively distributed and self-adaptive solutions for virtual worlds suitable to run in the cloud. The results, in terms of number of avatars per CPU, exceed by orders of magnitude the performances of current state-of-the-art implementations. This indicates Kiwano to be a cost effective solution for the industry. The open API for our first implementation is available at \url{http://kiwano.li}.La réalité mixe, les jeux en ligne massivement multijoueur (MMOGs), les mondes virtuels et le cyberespace sont des concepts extrêmement attractifs. Mais leur déploiement à large échelle reste difficile et il est en conséquence souvent évité.La contribution principale de la thèse réside dans le système distribué Kiwano, qui permet à un nombre illimité d'avatars de peupler et d'interagir simultanément dans un même monde contigu. Dans Kiwano nous utilisons la triangulation de Delaunay pour fournir à chaque avatar un nombre constant de voisins en moyenne, indépendamment de leur densité ou distribution géographique. Le nombre d'interactions entre les avatars et les calculs inhérents sont bornés, ce qui permet le passage à l'échelle du système.La charge est repartie sur plusieurs machines qui regroupent sur un même nœud les avatars voisins de façon contiguë dans le graphe de Delaunay. L'équilibrage de la charge se fait de manière contiguë et dynamique, en suivant la philosophie des réseaux pair-à-pair (peer-to-peer overlays). Cependant ce principe est adapté au contexte de l'informatique dématérialisée (cloud computing).Le nombre optimal d'avatars par CPU et les performances de notre système ont été évalués en simulant des dizaines de milliers d'avatars connectés à la même instance de Kiwano tournant à travers plusieurs centres de traitement de données.Nous proposons également trois applications concrètes qui utilisent Kiwano : Manycraft est une architecture distribuée capable de supporter un nombre arbitrairement grand d'utilisateurs cohabitant dans le même espace Minecraft, OneSim, qui permet à un nombre illimité d'usagers d'être ensemble dans la même région de Second Life et HybridEarth, un monde en réalité mixte où avatars et personnes physiques sont présents et interagissent dans un même espace: la Terre

Mega - mobile multimodal extended games

Tese de mestrado em Engenharia Informática, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2012As aplicações de entretenimento móvel têm hoje em dia um papel importante e significativo no mercado de software, abrangendo um grupo variado de utilizadores. Tudo isto se deve ao repentino sucesso de dispositivos de interacção inovadora, como o Wiimote da Nintendo, o Move da Sony e o Kinect da Microsoft. Por sua vez estas técnicas de interacção multimodal têm sido exploradas para jogos móveis. A recente geração de dispositivos móveis vem equipada com uma grande variedade de sensores, para além dos óbvios como ecrã táctil e microfone. Existem ainda outros componentes interessantes como bússola digital, acelerómetros, sensores ópticos. Os dispositivos móveis são também utilizados como máquina fotográfica digital, agenda pessoal, assim como para ver videos e ouvir música, e claro, para jogar jogos. Olhar para os novos grupos de utilizadores e para as novas formas de jogar e incluir nos jogos formas de interacção novas, usando os atributos e potencialidades de novas plataformas e novas tecnologias é pois um assunto pungente e deveras desafiante. Com este trabalho pretende-se estudar e propor novas dimensões de jogo e interacção com plataformas móveis, sejam smartphones, sejam tablets, que se adequem às mais distintas comunidades de jogadores. Pretende-se sobretudo explorar modalidades alternativas como as baseadas no tacto e vibração, assim como no áudio, combinadas ou não com outras mais tradicionais de foro visual. Almeja-se ainda explorar jogos em grupo, à distância e co-localizados, encontrando e estudando novas formas de expressão em jogos clássicos e jogos inovadores que envolvam pequenos conjuntos de indivíduos. A ubiquidade inerente aos dispositivos móveis faz ainda com que se tenham que encontrar neste jogos de grupo formas de fluxo de jogo que sustentem saídas e entradas rápidas ou menos rápidas sem que ainda assim se perca o interesse e a motivação de jogar. Este trabalho iniciou-se com uma pesquisa intensiva de trabalho relacionado, sobre a área de jogos móveis e suas multimodalidades, passando consequentemente pela acessibilidade inerente, jogos em grupo e suas formas de comunicação e conexão, e por último dando especial atenção a jogos de puzzle, sendo o tipo de jogo focado neste trabalho. Seguidamente, foi efectuado o levantamento de requisitos e exploradas as opções de jogo e de interacção relativas a jogos de puzzle móveis multimodais. No âmbito deste estudo foram criados três pequenos jogos sobre um conceito comum: jogos de puzzle. A primeira aplicação contém três modalidades diferentes de jogo: uma visual, apresentando um jogo de puzzle de imagens baseado nos tradicionais; uma segunda auditiva, que recria o conceito de jogo através de música, tornando as peças em pequenas parcelas sonoras da música de tamanhos equivalentes; e a terceira háptica, criando deste modo um puzzle com peças de padrões vibratórios diferentes. A segunda aplicação recriou o mesmo conceito de jogo, puzzle, no modo audio, mas retirando toda a informação visual, apresentando simples formas de interacção. A terceira aplicação apresenta uma abordagem sobre os jogos em grupo, permitindo jogar puzzles visuais e de audio em dois modos distintos: cooperativo, onde os jogadores têm de jogar em equipa de forma a conseguir completar o puzzle; e competitiva, onde os jogadores são forçados a ser mais rápidos que o adversário de modo a poderem vencer. Todas estas aplicações permitem ao utilizador definir o tamanho do puzzle e o nível de dificuldade, assim como escolher as imagens e músicas que pretendem resolver em forma de puzzle. Foram conduzidos vários testes de utilizador, nomeadamente um para cada aplicação desenvolvida. Sobre a primeira aplicação vinte e quatro participantes jogaram puzzles visuais e auditivos, distribuídos equitativamente pelas modalidades. Deste modo, cada participante resolveu nove puzzles de imagem ou nove puzzles audio distintos. Neste primeiro estudo procurou descobrir-se as estratégias de resolução dos puzzles, procurando principalmente igualdades e diferenças entre os diferentes modos. Para o segundo estudo foi usada a segunda aplicação desenvolvida, e foram abrangidos novamente vinte e quatro utilizadores, doze dos quais sendo cegos. Cada participante resolveu três puzzles audio diferentes. Relativamente a este estudo, foi proposta uma comparação entre os modos estudados anteriormente, especialmente sobre o modo audio, uma vez que foi usado o mesmo procedimento. Para os utilizadores cegos o objectivo foi provar que seria possível criar um jogo divertido, desafiante e sobretudo acessível a partir de um conceito de jogo clássico. Para o último estudo, vinte e quatro participantes, organizados em pares, jogaram puzzles visuais e de audio em modo cooperativo e competitivo. Cada conjunto de participantes resolveu quatro puzzles, um para cada modo de jogo por cada tipo de puzzle, o que significa dois puzzles visuais, um competitivo e outro cooperativo, e dois puzzles audio, sendo também um cooperativo e outro competitivo. O objectivo mais uma vez foi procurar as estratégias de resolução, permitindo também a comparação com outros modos anteriormente estudados. Todos os jogos foram transformados em dados contendo todas as acções que cada jogador tomou durante a resolução do puzzle. Esses dados foram depois transformados em números específicos de forma a poderem ser analisados e discutidos. Os valores obtidos foram divididos em três grupos principais, as tentativas de colocação de peças, o número de ajudas, e o tempo de conclusão do puzzle. Em relação às tentativas de colocação de peças é possível identificar a ordem correspondente segundo três formas distintas, pela classificação do tipo de peças, pela disposição das peças na fita e pela ordem sequencial do puzzle. Os resultados do estudo mostram que uma mesma estratégia de resolução de puzzles é usada através de todos os modos estudados, os jogadores optam por resolver primeiro as zonas mais relevantes do puzzle, deixando as partes mais abstractas e confundíveis para o final. No entanto, parente novas modalidades de jogo, pequenas percentagens de utilizadores mostraram diferentes estratégias de resolução. Através das opiniões dos utilizadores é também possível afirmar que todas as aplicações desenvolvidas são jogáveis, divertidas e desafiantes. No final foi criado um conjunto de componentes reutilizáveis e um conjunto de parâmetros para a criação de novos jogos. Numa linha de trabalho futuro foram propostos vários objectivos interessantes que podem promover e reaproveitar o trabalho desenvolvido. Deste modo foi criado um jogo de puzzle baseado na primeira aplicação desenvolvida, mantendo os modos visual e audio, de forma a poder integrar no mercado de aplicações móveis, permitindo deste modo, um estudo em larga escala sobre os mesmos conceitos estudados neste trabalho. Foi também pensada a criação de um servidor centralizado, permitindo conter os resultados de todos os jogadores de forma a criar um ranking geral, podendo deste modo incentivar os jogadores a melhorar o seu desempenho, e ajudar a promover o próprio jogo. Outra alternativa passa por melhorar e aperfeiçoar o modo háptico, de forma a criar mais uma modalidade viável sobre o mesmo conceito de jogo, de forma a poder ser também estudada de forma equivalente. O puzzle para invisuais pode também ser melhorado e aperfeiçoado de forma a criar mais desafios através da inclusão dum modo háptio. E por fim, não menos importante, criar novas dimensões de jogo em grupo, permitindo jogar os modos cooperativo e competitivo em simultâneo, tendo por exemplo duas equipas de dois jogadores cada, a cooperar entre si para completar o puzzle, e de certa forma a competir contra a outra equipa para terminar primeiro e com melhores resultados. O objectivo seria, mais uma vez, estudar as estratégias usadas.Mobile entertainment applications have an important and significant role in the software market, covering a diverse group of users. All this is due to the sudden success of innovative interaction devices such as Nintendo’s Wiimote, Sony’s Move and Kinect’s Microsoft. On the other hand, these multimodal interaction techniques have been explored for mobile games. The latest generation of mobile devices is equipped with a wide variety of sensors, in addition to the obvious such as touch screen and microphone. There are other interesting components such as digital compass, accelerometers and optical sensors. Mobile devices are also used as a digital camera, personal organizer, to watch videos and listen to music, and of course, to play games. Looking for the new users groups and for the new ways to play the games and include new forms of interaction, using the attributes and capabilities of new platforms and new technologies is an issue as poignant and very challenging. This work aims to study and propose new dimensions of play and interaction with mobile platforms, whether smartphones or tablets, which suit most distinct communities of players. It is intended primarily to explore alternative modalities such as touch-based and vibratory, as well as audio based, combined or not with traditional visual ones. It also aims at exploring group games, spatially distributed and co-located, finding and studying new forms of expression in classic games and innovative games that involve small sets of individuals. The ubiquity inherent to mobile devices leads us to find input and output flows which support rapid or less rapid entry commands, without losing the interest and motivation to play. In addition to the design and implementation of three or four small game applications intended to create a set of reusable components and a set of guidelines for creating new games

A Systematic Mapping Study of MMOG Backend Architectures

The advent of utility computing has revolutionized almost every sector of traditional software development. Especially commercial cloud computing services, pioneered by the likes of Amazon, Google and Microsoft, have provided an unprecedented opportunity for the fast and sustainable development of complex distributed systems. Nevertheless, existing models and tools aim primarily for systems where resource usage—by humans and bots alike—is logically and physically quite disperse resulting in a low likelihood of conflicting resource access. However, a number of resource-intensive applications, such as Massively Multiplayer Online Games (MMOGs) and large-scale simulations introduce a requirement for a very large common state with many actors accessing it simultaneously and thus a high likelihood of conflicting resource access. This paper presents a systematic mapping study of the state-of-the-art in software technology aiming explicitly to support the development of MMOGs, a class of large-scale, resource-intensive software systems.By examining the main focus of a diverse set of related publications, we identify a list of criteria that are important for MMOG development. Then, we categorize the selected studies based on the inferred criteria in order to compare their approach, unveil the challenges faced in each of them and reveal research trends that might be present. Finally we attempt to identify research directions which appear promising for enabling the use of standardized technology for this class of systems

Managing Network Delay for Browser Multiplayer Games

Latency is one of the key performance elements affecting the quality of experience (QoE) in computer games. Latency in the context of games can be defined as the time between the user input and the result on the screen. In order for the QoE to be satisfactory the game needs to be able to react fast enough to player input. In networked multiplayer games, latency is composed of network delay and local delays. Some major sources of network delay are queuing delay and head-of-line (HOL) blocking delay. Network delay in the Internet can be even in the order of seconds. In this thesis we discuss what feasible networking solutions exist for browser multiplayer games. We conduct a literature study to analyze the Differentiated Services architecture, some salient Active Queue Management (AQM) algorithms (RED, PIE, CoDel and FQ-CoDel), the Explicit Congestion Notification (ECN) concept and network protocols for web browser (WebSocket, QUIC and WebRTC). RED, PIE and CoDel as single-queue implementations would be sub-optimal for providing low latency to game traffic. FQ-CoDel is a multi-queue AQM and provides flow separation that is able to prevent queue-building bulk transfers from notably hampering latency-sensitive flows. WebRTC Data-Channel seems promising for games since it can be used for sending arbitrary application data and it can avoid HOL blocking. None of the network protocols, however, provide completely satisfactory support for the transport needs of multiplayer games: WebRTC is not designed for client-server connections, QUIC is not designed for traffic patterns typical for multiplayer games and WebSocket would require parallel connections to mitigate the effects of HOL blocking