Building a scalable social game server

When building web applications with a broad target group, there is always a possibility that the user count will increase dramatically in a short period of time. Especially when building social application with a potential network effect. In such cases it is important to forestall scalability problems by implementing a scalable design from start. Often the scalability problems emerge at first when it is too late and the application has to be rewritten. Methods, architectures and techniques for building scalable applications are needed as well as methods for verifying scalability before the application is launched. This thesis explores the issue of scalability through the development and testing of an online word game. In the process of doing so, the thesis discusses the definition of scalability, how it is measured and how it is achieved is discussed through a literature study. Further on a scalable architecture is derived from the literature and a complete word game is implemented using the JavaScript based framework node.js. In addition to the server side application, a web browser client is developed to test the server functionality. For server persistence, the NoSQL key value store database Couchbase is used to allow horizontal storage scaling. Player simulations are implemented to mimic real game play to render server load. The simulations record measures such as response time when playing the game at different scaling parameters such as the number of web servers and database nodes in the database cluster at varying number of players. As a result of the implementation, a functional, playable game is completed. The results show some indication of scalability as decreased response time when increasing the number of web server instances. An unidentified problem with the database cluster prevented the simulations going beyond 8000 players as the database cluster becomes the bottleneck. The planned time was not sufficient to solve the unexpected database cluster problem and thus, the final measurements to determine the level of scalability could not be completed. But the conceptual architectural design can be regarded as horizontally scalable with support from the literature

On the non-linearity of the willingness to commute

Established analysis of labour market commuting are based on random choice models and gravity type models. In these models generalised transport costs are formulated as exponential or loglinear distance-dependent functions. This paper presents empirical observations that imply that time-distances influence the commuting behaviour in a non-linear way, such that the time sensitivity is much lower for very short and long distances, whereas intermediate distance display a high time sensitivity. This is explained in a model which is parametrised and estimated. The results are important for understanding and predicting commuter behaviour. It also helps to delineate space, as in classical traditions, into local, intra-regional, and extra-regional space.

Intermittent Connectivity for Exploration in Communication-Constrained Multi-Agent Systems

Motivated by exploration of communication-constrained underground environments using robot teams, we study the problem of planning for intermittent connectivity in multi-agent systems. We propose a novel concept of information-consistency to handle situations where the plan is not initially known by all agents, and suggest an integer linear program for synthesizing information-consistent plans that also achieve auxiliary goals. Furthermore, inspired by network flow problems we propose a novel way to pose connectivity constraints that scales much better than previous methods. In the second part of the paper we apply these results in an exploration setting, and propose a clustering method that separates a large exploration problem into smaller problems that can be solved independently. We demonstrate how the resulting exploration algorithm is able to coordinate a team of ten agents to explore a large environment

Market Potential and Distance Decay - Growth and decline of sectors across locations in urban regions

This paper introduces a model which identifies the economic activity of each local economy (location) and observes the time distance between each pair of locations as well as the average time distance between sub locations in each local economy. We focus on three categories of firms: (i) manufacturing, (ii) KIBS, and (iii) other services and model how they increase and decrease their employment in each location in response to the location?s market potential. The response mechanism allows for non-linearities and aims to show how the dynamic response differs for the three categories of firms. In the econometric analysis the market potential of each location is determined endogenously, and this also makes it possible to determine the geographic extension of urban regions. This exercise also includes an endogenous determination of sector-specific distance-decay parameters. The model succeeds in depicting the gradual increase of service activities in certain locations and manufacturing activities in others

Success in manufacturing employment in an industrial district: Higher productivity or lower wages?

The south-western part of the county of Jonkoping in Sweden has an industrial structure that is very different from that in the rest of Sweden. The region which may be characterised as an ?industrial district?, is dominated by small and medium-sized enterprises. It is well-known for its entrepreneurial spirit and in the international literature it has been compared with other entrepreneurial regions, such as ?the third Italy?, Rhone-Alps, Baden-Wurttemberg, and Silicon Valley. The employment share for manufacturing in the region is approximately double that of the rest of Sweden. This pattern seems to be very stable over time. Industries which are declining in other parts of Sweden are actually expanding in this region. The purpose of the current paper is to try to explain why the manufacturing industry is so successful in this region. In the paper we test a number of different hypotheses. In particular, we investigate whether the apparent success is the result of higher productivity growth or if it is the result of low input costs, mainly low wages. Differences in productivity growth or in input costs might be the result of the existence of particular types of agglomeration economies. In the paper we investigate the role of such economies. In the analysis we use productivity and gross profit distributions of Salter type. These distributions we estimate by using data on sales value, value added and wages for the manufacturing industry in Sweden for various years collected by Statistics Sweden

Regional Characteristics and the Survival of New Firms

There is an abundant literature on industrial ecology aiming at explaining the survival propensity of recently started firms. The majority of the contributions concentrate on the characteristics of the entrepreneur, the new firm or the industry. Only a small minority of the existing studies consider the influence of the location where the new firm has been started on survival probability. The evidence of the importance of location in the literature is mixed. However, only a limited share of these studies analyzes the importance of localized external economies of scale for the survival of newly founded firms. This relative lack of studies is intriguing since, for example, the ?new economic geography? theory empha-sizes the role that clusters of individual industries and of complementary industries within a distinct geographical area play in terms of proximity and network externalities. Thus, a basic motivation for this paper is that the absolute majority of business survival studies disregard the fundamental facts that every new firm is started in a specific location. A second motivation is the fact that in many of the studies that include spatial factors as explanatory factors the representation of these factors are often not ideal. A third motivation is that the representation of geographical space has not taken into consideration of the importance of the hierarchical structure of geographical space. The purpose of this paper is to test the influence of demand and supply conditions and general economic milieu in localities on the survival of newly founded firms while controlling for firm and industry characteristics and using a proper representation of the hierarchical structure of geographical space

Skills, education and productivity in the KIBS sector: firm level evidence on the presence of externalities

Increased productivity is one of the main drivers of economic growth. Considering the increasing importance of the service sector in many economies studies of productivity in service firms are essential, but still rare. Questions concerning the underlying reasons for productivity differences in service firms are therefore important. Why is the productivity in certain firms higher than in others and what are the possibilities for less-productive firms to increase their productivity levels? This paper aims to examine these issues with a particular focus on the importance of externalities. Externalities are defined as region-specific economic effects influencing firm efficiency. These externalities can be broadly divided in the following categories: i) urbanization economies which relate to diversity and density (Jacobs externalities), ii) localization economies which concern specialization and concentration (MAR externalities), iii) competition (Porter externalities), and iv) labor market externalities. The purpose of the paper is to explain the productivity levels of Swedish service firms using measures of these externalities. However, also firm specific characteristics, including characteristics of the workforce, are included. These are used both as control variables and to capture potential spillover effects that indirectly affect productivity through the employees. The characteristics of the workforce are essential to include since the employees have the potential to affect the way different firms absorb and use possible spillover effects. They are therefore a crucial component to channel externalities to the firm as a whole. This is the case especially for service firms since these are generally very labor intensive. The results of this study should be of interest to policy makers since they have the possibility to make decisions that contribute to more productive regional environments. This is also of interest to company leaders since they have the possibility to decide where to locate and how to structure their firms in order to take advantage of productivity enhancing externalities

On the non-linearity of the willingness to commute

Established analysis of labour market commuting are based on random choice models and gravity type models. In these models generalised transport costs are formulated as exponential or loglinear distance-dependent functions. This paper presents empirical observations that imply that time-distances influence the commuting behaviour in a non-linear way, such that the time sensitivity is much lower for very short and long distances, whereas intermediate distance display a high time sensitivity. This is explained in a model which is parametrised and estimated. The results are important for understanding and predicting commuter behaviour. It also helps to delineate space, as in classical traditions, into local, intra-regional, and extra-regional space

Intermittent Connectivity for Exploration in Communication-Constrained Multi-Agent Systems

Motivated by exploration of communication-constrained underground environments using robot teams, we study the problem of planning for intermittent connectivity in multi-agent systems. We propose a novel concept of information-consistency to handle situations where the plan is not initially known by all agents, and suggest an integer linear program for synthesizing information-consistent plans that also achieve auxiliary goals. Furthermore, inspired by network flow problems we propose a novel way to pose connectivity constraints that scales much better than previous methods. In the second part of the paper we apply these results in an exploration setting, and propose a clustering method that separates a large exploration problem into smaller problems that can be solved independently. We demonstrate how the resulting exploration algorithm is able to coordinate a team of ten agents to explore a large environment