Context. Modern code review tools such as Gerrit have made available great amounts of code review data from different open source projects as well as other commercial projects. Code reviews are used to keep the quality of produced source code under control but the stored data could also be used for evaluation of the software development process. Objectives. This thesis uses machine learning methods for an approximation of review expert’s performance evaluation function. Due to limitations in the size of labelled data sample, this work uses semisupervised machine learning methods and measure their influence on the performance. In this research we propose features and also analyse their relevance to development performance evaluation. Methods. This thesis uses Radial Basis Function networks as the regression algorithm for the performance evaluation approximation and Metric Based Regularisation as the semi-supervised learning method. For the analysis of feature set and goodness of fit we use statistical tools with manual analysis. Results. The semi-supervised learning method achieved a similar accuracy to supervised versions of algorithm. The feature analysis showed that there is a significant negative correlation between the performance evaluation and three other features. A manual verification of learned models on unlabelled data achieved 73.68% accuracy. Conclusions. We have not managed to prove that the used semisupervised learning method would perform better than supervised learning methods. The analysis of the feature set suggests that the number of reviewers, the ratio of comments to the change size and the amount of code lines modified in later parts of development are relevant to performance evaluation task with high probability. The achieved accuracy of models close to 75% leads us to believe that, considering the limited size of labelled data set, our work provides a solid base for further improvements in the performance evaluation approximation.

This thesis presents an evaluation of the Solaris version of the Xen virtual machine monitor and a comparison of its performance to the performance of Solaris Containers under similar conditions. Xen is a virtual machine monitor, based on the paravirtualization approach, which provides an instruction set different to the native machine environment and therefore requires modifications to the guest operating systems. Solaris Zones is an operating system-level virtualization technology that is part of the Solaris OS. Furthermore, we provide a basic performance evaluation of the security modules for Xen and Zones, known as sHype and Solaris Trusted Extensions, respectively. We evaluate the control domain (know as Domain-0) and the user domain performance as the number of user domains increases. Testing Domain-0 with an increasing number of user domains allows us to evaluate how much overhead virtual operating systems impose in the idle state and how their number influences the overall system performance. Testing one user domain and increasing the number of idle domains allows us to evaluate how the number of domains influences operating system performance. Testing concurrently loaded increasing numbers of user domains we investigate total system efficiency and load balancing dependent on the number of running systems. System performance was limited by CPU, memory, and hard drive characteristics. In the case of CPU-bound tests Xen exhibited performance close to the performance of Zones and to the native Solaris performance, loosing 2-3% due to the virtualization overhead. In case of memory-bound and hard drive-bound tests Xen showed 5 to 10 times worse performance.

The emergence of real-time applications, like Voice over IP and video conferencing, in IP networks implies a challenge to the underlying infrastructure. Several real-time applications have requirements on timeliness as well as on reliability and are accompanied by signaling applications to set up, tear down and control the media sessions. Since neither of the traditional transport protocols responsible for end-to-end transfer of messages was found suitable for signaling traffic, the Stream Control Transmission Protocol (SCTP) was standardized. The focus for the protocol was initially on telephony signaling applications, but it was later widened to serve as a general purpose transport protocol. One major new feature to enhance robustness in SCTP is multihoming, which enables for more than one path within the same association. In this thesis we evaluate some of the mechanisms affecting transmission performance in case of a switchover between paths in a multihomed SCTP session. The major part of the evaluation concerns a failure situation, where the current path is broken. In case of failure, the endpoint does not get an explicit notification, but has to react upon missing acknowledgements. The challenge is to distinguish path failure from temporary congestion to decide  when to switch to an alternate path. A too fast switchover may be spurious, which could reduce transmission performance, while a too late switchover also results in reduced transmission performance. This implies a tradeoff which involves several protocol as well as network parameters and we elaborate among these to give a coherent view of the parameters and their interaction. Further, we present a recommendation on how to tune the parameters to meet  telephony signaling requirements, still without violating fairness to other traffic. We also consider another angle of switchover performance, the startup on the alternate path. Since the available capacity is usually unknown to the sender, the transmission on a new path is started at a low rate and then increased as acknowledgements of successful transmissions return. In case of switchover in the middle of a media session the startup phase after a switchover could cause problems to the application. In multihomed SCTP the availability of the alternate path makes it feasible for the end-host to estimate the available capacity on the alternate path prior to the switchover. Thus, it would be possible to implement a more efficient startup scheme. In this thesis we combine different switchover scenarios with relevant traffic. For these combinations, we analytically evaluate and quantify the potential performance gain from utilizing an ideal startup mechanism as compared to the traditional startup procedure.

Embedded microcomputers are used in a wide range of applications nowadays. Avionics is one of these areas and requires extra attention regarding reliability and determinism. Thus, these issues should also be born in mind in addition to performance when evaluating embedded microcomputers. This master thesis suggests a framework for performance evaluation of two members of the PowerPC microprocessor family, namely the MPC5554 from Freescale and PPC440EPx from AMCC, and analyzes the results within and between these processors. The framework can be generalized to be used in any microprocessor family, if required. Apart from performance evaluation, this thesis also suggests also a new terminology by introducing the concept of determinism levels to be able to estimate determinism issues in avionics applications more clearly, which is crucial regarding the requirements and working conditions of this very application. Such estimation does not include any practical results as in performance evaluation, but rather remains theoretical. Similar to Automark™ used by AutoBench™ in the EEMBC Benchmark Suite, we introduce a new performance metric score that we call ”Aviomark” and we carry out a detailed comparison of Aviomark with the traditional Automark™ score to be able to see how Aviomark differs from Automark™ in behavior. Finally, we have developed a graphical user interface (GUI) which works in parallel with the Green Hills MULTI Integrated Development Environment (IDE) in order to simplify and automate the evaluation process. By the help of the GUI, the users will be able to easily evaluate their specific PowerPC processors by starting the debugging from MULTI IDE.

In the last decade, we have seen an explosive growth in the deployment of multimedia applications on the Internet. However, the transport service provided over the Internet is not always feasible for these applications, since the network was originally designed for other types of applications. One way to better accommodate the service requirements of some of these applications is to provide a partially reliable transport service. A partially reliable transport service does not insist on recovering all, but just some of the packet losses, thus providing a lower transport delay than a reliable transport service. The work in this thesis focuses on the design, implementation, and evaluation of a partially reliable transport protocol called PRTP. PRTP has been designed as an extension to TCP in order to show that such a service could be effectively integrated with current protocol standards. An important feature of PRTP is that all modifications for PRTP are restricted to the receiver side, which means that it could be very easily deployed. The thesis presents performance results from various experiments on a Linux implementation of PRTP. The results suggest that transfer times can be decreased significantly when using PRTP as opposed to TCP in networks in which packet loss occurs. Furthermore, the thesis includes a study that investigates how users perceive an application that is based on a partially reliable service. Specifically, how users select the trade-off between image quality and latency when they download Web pages is explored. The results indicate that many of the users in the study could accept less than perfect image quality if the latency could be shortened.

Context: Chat applications have been around since the beginning of the modern internet. Today, there are many different chat systems with various communication solutions, but only a few utilize the fully decentralized Peer-to-Peer concept. Objectives: In this report, we want to investigate to see if a fully decentralized P2P concept is a suitable choice for chat applications. In order to investigate, a P2P architecture was selected and a simulation was implemented in Java. The simulation was used to make a performance evaluation in order see if the P2P concept could meet the requirements of a chat application, and to identify problems and difficulties. Methods: Two main methods were used in this thesis. First, a qualitative design method was used to identify and discuss different possibilities of designing a distributed chat application. Second, a performance evaluation was conducted to verify the selected and implemented mechanisms are able to obtain their general performance capabilities and to tune them towards anticipated performance. Results: The simulation proved that a decentralized P2P system can scale and find resources in a network quite efficiently without the need of any centralized service. It also proved to be simpler for the user to use the P2P concept, as no special configurations are needed. However, the selected protocol (Chord) had problems with high rates of churn, which could cause problems in big chat environments. The P2P concept was also shown to be highly complex to implement. Conclusion: P2P technology is a more complex technology, but it gives the host a lower cost in terms of hardware and maintenance. It also makes the system more robust and fault-tolerant. As we have seen in this report, P2P can scale and find other resources efficiently without the need of a centralized service. However, it will consume more power for each user, which makes mobile devices bad peers.

This dissertation describes a project to create a prototype application for Google Glass,where the purpose is to help assembly line industries by allowing workers to see instructionsvisually while working with both hands free. This solves the problem of requiringan instruction manual since instead all instructions will be stored in a database. GoogleGlass retrieves and displays the information for the user after scanning a QR-code forthe product which is going to be assembled. An important aspect is to see if such a systemis powerful enough for industries to start working with Google Glass. This conceptwas developed into a working prototype system, where Google Glass can retrieve data byscanning a QR-code that contains information about a specific product. This informationwill give a step by step instruction on which components the product contains and theinstructions for assembling them. The results presented in this dissertation shows thatGoogle Glass is not suited for the industry at its current state.

More than three decades ago the notion of trust was introduced into the management accounting (MA) literature, and a growing stream of empirical papers elaborating on the relation between MA controls and trust signals the importance andvitality of this research area. However, a closer look at the literature shows that while major insights have been made, there is also considerable confusion around both research models and the meanings of key concepts. Accordingly, the time seems opportune to conduct an extended and critical review of the legacies of this literature. More precisely, the aims of the study are to (i) analyze how MA and trust have been conceptualized and related to each other; (ii) identify weaknesses andknowledge gaps in the literature; and, (iii) based on these, suggest how the literature may be synthesized and developed in the future. In so doing, this thesis analyses 37 empirical studies focusing specifically on the association between MA and trust. Overall, two key findings emerge from the analysis. A first key finding is that the area can be characterized as fragmented. More specifically, many different terms are used to denote similar concepts, and vice versa. The literature is also characterized by different levels of analysis, and different, potentially conflicting research models. The literature is also underpinned by different theoretical perspectives, of which some have conflicting assumptions. The second key finding is that there are several knowledge gaps and weaknesses in th eliterature. For example, while a majority of studies shows that MA is a factor affecting trust, MA itself is oftentimes left unexplained. Also, many studies conceptualize trust from the perspective of only one party in a relationship, and the questions of how and why MA and trust (co)develops and emerges over time are largely unaddressed. Furthermore, while researchers have empirically studied both personal trust and system trust, respectively, no one has modelled how they may be interrelated. Based on these findings, a model is proposed which not only synthesizes the extant literature, but also indentifies new, potentially important associations between different MA and trust factors. The model—consisting of twelve propositions—also theorizes how these factors affect each other over time. The thesis concludes with a number of suggestions for how to develop this research area in the future.

The diploma thesis is prepared in cooperation with the company XY a.s. and it deals with the system of remuneration and employee evaluation. Through the analysis of the current situation and by means of a questionnaire, it assesses the state of the above mentioned areas within the company. Based on results of the research, recommendations regarding the system of remuneration and employee evaluation are suggested.

Abstract Peer-to-Peer (P2P) networking changes the way of people utilizing Internet, for example, sharing and consuming digital content, from the ground up. It continues to show its power and strength when it is combined with other emerging technologies, such as Web Services. This thesis contributes to the research and development of P2P networks from four aspects. Firstly, a P2P and Web Services converged multiple-tier system architecture is proposed. The architecture proposed enables providing Web Services in the context of heterogeneous access networks in an efficient way by utilizing P2P paradigm. A lightweight middleware architecture is introduced to fit the diversified mobile terminals. A theoretical analysis is given to provide a comparative study with the conventional centralized architecture. Secondly, a General Truncated Pyramid Peer-to-Peer (GTPP) architecture is presented to analyze the performance of hierarchical architecture compared with flat architecture. The motivation behind the GTPP architecture is to see whether an added tier can bring with it added value and functionality. A detailed mathematical analysis is provided which takes into consideration various performance metrics, including the lookup hopcount, lookup latency, maintenance traffic from a single peer point of view, and maintenance traffic from the whole system point of view. Furthermore, simulation results with respect to the lookup hopcount are also provided. Through mathematical analysis and simulation results, an optimal value regarding the number of tiers of the GTPP architecture is found, showing that 2~3 tiers are appropriate for most of situations. A specialized model is also proposed to improve the performance of hierarchical architecture. Thirdly, the performance evaluation of a communication-oriented Kademlia-based P2P system is provided in detail. NetHawk EAST-based simulation models and a prototype are both utilized to evaluate the performance. Simulation results from NetHawk EAST-based simulation models demonstrate the optimal design choices regarding the resource lookup parallelism degree and resource replication degree, and show the unnecessary existence of the messages used to detect the liveness of peers in a DHT overlay. Measurements from the prototype show the feasibility of mobile nodes acting as fully fledged overlay nodes from three different perspectives, namely CPU processing load, network traffic load, and battery consumption. The optimal size of packets which consumes battery in the most efficient way is also found through battery consumption measurements. Fourthly, the effects of different churn models on the performance of structured P2P networks are analyzed. Specifically, three typical churn models are analyzed to provide a comparative result. The simulation results show that the difference among the effects of different churn models on the performance of structured P2P networks is quantitative rather than qualitative. This provides some guidance for the selection of different churn models for the contemporary researchers.