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• 1. Abdulla, Parosh Aziz
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Bisimulation minimization of tree automata2007In: International Journal of Foundations of Computer Science, ISSN 0129-0541, Vol. 18, no 4, p. 699-713Article in journal (Refereed)

We extend an algorithm by Paige and Tarjan that solves the coarsest stable refinement problem to the domain of trees. The algorithm is used to minimize nondeterministic tree automata (NTA) with respect to bisimulation. We show that our algorithm has an overall complexity of $O(\hat{r} m \log n)$, where $\hat{r}$ is the maximum rank of any symbol in the input alphabet, m is the total size of the transition table, and n is the number of states.

• 2. Abdulla, Parosh Aziz
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Bisimulation minimization of tree automata2006In: Implementation and Application of Automata : 11th International Conference, CIAA 2006, 2006, p. 699-713Conference paper (Refereed)

We extend an algorithm by Paige and Tarjan that solves the coarsest stable refinement problem to the domain of trees. The algorithm is used to minimize nondeterministic tree automata (NTA) with respect to bisimulation. We show that our algorithm has an overall complexity of O ((r) over cap log n), where (r) over cap is the maximum rank of any symbol in the input alphabet, m is the total size of the transition table, and n is the number of states.

• 3.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
A Direct Method for 3D Hand Pose Recovery2014In: 22nd International Conference on Pattern Recognition, 2014, p. 345-350Conference paper (Refereed)

This paper presents a novel approach for performing intuitive 3D gesture-based interaction using depth data acquired by Kinect. Unlike current depth-based systems that focus only on classical gesture recognition problem, we also consider 3D gesture pose estimation for creating immersive gestural interaction. In this paper, we formulate gesture-based interaction system as a combination of two separate problems, gesture recognition and gesture pose estimation. We focus on the second problem and propose a direct method for recovering hand motion parameters. Based on the range images, a new version of optical flow constraint equation is derived, which can be utilized to directly estimate 3D hand motion without any need of imposing other constraints. Our experiments illustrate that the proposed approach performs properly in real-time with high accuracy. As a proof of concept, we demonstrate the system performance in 3D object manipulation. This application is intended to explore the system capabilities in real-time biomedical applications. Eventually, system usability test is conducted to evaluate the learnability, user experience and interaction quality in 3D interaction in comparison to 2D touch-screen interaction.

• 4.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
Self-supervised language grounding by active sensing combined with Internet acquired images and text2017In: Proceedings of the Fourth International Workshop on Recognition and Action for Scene Understanding (REACTS2017) / [ed] Jorge Dias George Azzopardi, Rebeca Marf, Málaga: REACTS , 2017, p. 71-83Conference paper (Refereed)

For natural and efficient verbal communication between a robot and humans, the robot should be able to learn names and appearances of new objects it encounters. In this paper we present a solution combining active sensing of images with text based and image based search on the Internet. The approach allows the robot to learn both object name and how to recognise similar objects in the future, all self-supervised without human assistance. One part of the solution is a novel iterative method to determine the object name using image classi- fication, acquisition of images from additional viewpoints, and Internet search. In this paper, the algorithmic part of the proposed solution is presented together with evaluations using manually acquired camera images, while Internet data was acquired through direct and reverse image search with Google, Bing, and Yandex. Classification with multi-classSVM and with five different features settings were evaluated. With five object classes, the best performing classifier used a combination of Pyramid of Histogram of Visual Words (PHOW) and Pyramid of Histogram of Oriented Gradient (PHOG) features, and reached a precision of 80% and a recall of 78%.

• 5.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Autonomous Object Category Learning for Service Robots Using Internet Resources2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

With the developments in the field of Artificial Intelligence (AI), robots are becoming smarter, more efficient and capable of doing more dififcult tasks than before. Recent progress in Machine Learning has revolutionized the field of AI. Rather than performing pre-programmed tasks, nowadays robots are learning things, and becoming more autonomous along the way. However, in most of the cases, robots need a certain level of human assistance to learn something. To recognize or classify daily objects is a very important skill that a service robot should possess. In this research work, we have implemented a fully autonomous object category learning system for service robots, where the robot uses internet resources to learn object categories. It gets the name of an unknown object by performing reverse image search in the internet search engines, and applying a verification strategy afterwards. Then the robot retrieves a number of images of that object from internet and use those to generate training data for learning classifiers. The implemented system is tested in actual domestic environment. The classification performance is examined against some object categories from a benchmark dataset. The system performed decently with 78:40% average accuracy on ve object categories taken from the benchmark dataset and showed promising results in real domestic scenarios. There are existing research works that deal with object category learning for robots using internet images. But those works use Human-in-the-loop models, where humans assist the robot to get the object name for using it as a search cue to retrieve training images from internet. Our implemented system eliminates the necessity of human assistance by making the task of object name determination automatic. This facilitates the whole process of learning object categories with full autonomy, which is the main contribution of this research.

Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
What is the Word for Engineering in Swedish: Swedish Students' Conceptions of their Discipline2007Report (Other academic)
• 7.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Parallel Algorithms and Library Software for the Generalized Eigenvalue Problem on Distributed Memory Computer Systems2016Licentiate thesis, comprehensive summary (Other academic)

We present and discuss algorithms and library software for solving the generalized non-symmetric eigenvalue problem (GNEP) on high performance computing (HPC) platforms with distributed memory. Such problems occur frequently in computational science and engineering, and our contributions make it possible to solve GNEPs fast and accurate in parallel using state-of-the-art HPC systems. A generalized eigenvalue problem corresponds to finding scalars y and vectors x such that Ax = yBx, where A and B are real square matrices. A nonzero x that satisfies the GNEP equation is called an eigenvector of the ordered pair (A,B), and the scalar y is the associated eigenvalue. Our contributions include parallel algorithms for transforming a matrix pair (A,B) to a generalized Schur form (S,T), where S is quasi upper triangular and T is upper triangular. The eigenvalues are revealed from the diagonals of S and T. Moreover, for a specified set of eigenvalues an associated pair of deflating subspaces can be computed, which typically is requested in various applications. In the first stage the matrix pair (A,B) is reduced to a Hessenberg-triangular form (H,T), where H is upper triangular with one nonzero subdiagonal and T is upper triangular, in a finite number of steps. The second stage reduces the matrix pair further to generalized Schur form (S,T) using an iterative QZ-based method. Outgoing from a one-stage method for the reduction from (A,B) to (H,T), a novel parallel algorithm is developed. In brief, a delayed update technique is applied to several partial steps, involving low level operations, before associated accumulated transformations are applied in a blocked fashion which together with a wave-front task scheduler makes the algorithm scale when running in a parallel setting. The potential presence of infinite eigenvalues makes a generalized eigenvalue problem ill-conditioned. Therefore the parallel algorithm for the second stage, reduction to (S,T) form, continuously scan for and robustly deflate infinite eigenvalues. This will reduce the impact so that they do not interfere with other real eigenvalues or are misinterpreted as real eigenvalues. In addition, our parallel iterative QZ-based algorithm makes use of multiple implicit shifts and an aggressive early deflation (AED) technique, which radically speeds up the convergence. The multi-shift strategy is based on independent chains of so called coupled bulges and computational windows which is an important source of making the algorithm scalable. The parallel algorithms have been implemented in state-of-the-art library software. The performance is demonstrated and evaluated using up to 1600 CPU cores for problems with matrices as large as 100000 x 100000. Our library software is described in a User Guide. The software is, optionally, tunable via a set of parameters for various thresholds and buffer sizes etc. These parameters are discussed, and recommended values are specified which should result in reasonable performance on HPC systems similar to the ones we have been running on.

• 8.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N). Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Distributed one-stage Hessenberg-triangular reduction with wavefront scheduling2018In: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 40, no 2, p. C157-C180Article in journal (Refereed)

A novel parallel formulation of Hessenberg-triangular reduction of a regular matrix pair on distributed memory computers is presented. The formulation is based on a sequential cacheblocked algorithm by K degrees agstrom et al. [BIT, 48 (2008), pp. 563 584]. A static scheduling algorithm is proposed that addresses the problem of underutilized processes caused by two-sided updates of matrix pairs based on sequences of rotations. Experiments using up to 961 processes demonstrate that the new formulation is an improvement of the state of the art and also identify factors that limit its scalability.

• 9.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N). Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Distributed one-stage Hessenberg-triangular reduction with wavefront scheduling2016Report (Other academic)

A novel parallel formulation of Hessenberg-triangular reduction of a regular matrix pair on distributed memory computers is presented. The formulation is based on a sequential cache-blocked algorithm by Kågstrom, Kressner, E.S. Quintana-Ortí, and G. Quintana-Ortí (2008). A static scheduling algorithm is proposed that addresses the problem of underutilized processes caused by two-sided updates of matrix pairs based on sequences of rotations. Experiments using up to 961 processes demonstrate that the new algorithm is an improvement of the state of the art but also identifies factors that currently limit its scalability.

• 10.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
A parallel QZ algorithm for distributed memory HPC systems2014In: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 36, no 5, p. C480-C503Article in journal (Refereed)

Appearing frequently in applications, generalized eigenvalue problems represent one of the core problems in numerical linear algebra. The QZ algorithm of Moler and Stewart is the most widely used algorithm for addressing such problems. Despite its importance, little attention has been paid to the parallelization of the QZ algorithm. The purpose of this work is to fill this gap. We propose a parallelization of the QZ algorithm that incorporates all modern ingredients of dense eigensolvers, such as multishift and aggressive early deflation techniques. To deal with (possibly many) infinite eigenvalues, a new parallel deflation strategy is developed. Numerical experiments for several random and application examples demonstrate the effectiveness of our algorithm on two different distributed memory HPC systems.

• 11.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N). Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Parallel Variants of the Multishift QZ Algorithm with Advanced Deflation Techniques2007In: Applied Parallel Computing - State of the Art in Scientific Computing: 8th International Workshop, PARA 2006, Springer , 2007, p. 117-126Conference paper (Refereed)

The QZ algorithm reduces a regular matrix pair to generalized Schur form, which can be used to address the generalized eigenvalue problem. This paper summarizes recent work on improving the performance of the QZ algorithm on serial machines and work in progress on a novel parallel implementation. In both cases, the QZ iterations are based on chasing chains of tiny bulges. This allows to formulate the majority of the computation in terms of matrix-matrix multiplications, resulting in natural parallelism and better performance on modern computing systems with memory hierarchies. In addition, advanced deflation strategies are used, specifically the so called aggressive early deflation, leading to a considerable convergence acceleration and consequently to a reduction of floating point operations and computing time.

• 12.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N). SB–MATHICSE–ANCHP, EPF Lausanne.

Given a general matrix pair (A,B) with real entries, we provide software routines for computing a generalized Schur decomposition (S, T). The real and complex conjugate pairs of eigenvalues appear as 1×1 and 2×2 blocks, respectively, along the diagonals of (S, T) and can be reordered in any order. Typically, this functionality is used to compute orthogonal bases for a pair of deflating subspaces corresponding to a selected set of eigenvalues. The routines are written in Fortran 90 and targets distributed memory machines.

• 13.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
CONGESTION-CONTROLLED AUTOTUNING OF OPENMP PROGRAMS2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

Parallelisation is becoming more and more important as the single core performance increase is stagnating while the amount of cores is increasing with every new generation of hardware. The traditional approach of manual parallelisation has an alternative in parallel frameworks, such as OpenMP, which can simplify the creation of parallel code. Optimising this code can, however, be cumbersome and difficult. Automating the optimisation or tuning of parallel code and computations is a very interesting alternative to manually optimising algorithms and programs. Previous work has shown that intricate systems can effectively autotune parallel programs with potentially the same effectiveness as human experts. This study suggests using an approach with the main algorithm used inspired from the congestion control algorithms from computer networks, namely AIMD. By applying the algorithm on top of an OpenMP program the parallel parameters such as grain size can be controlled. Thee simplied algorithm is shown to be able to achieve a 19% speedup compared to a naive static parallel implementation

• 14.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Audio Video Streaming Solution for Bambuser2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis

Audio/Video streaming has widely been used in different applications but the social communication applications have especially raised its usage. The aim of this thesis is to design and develop an improved Audio/Video streaming solution for a Swedish company Bambuser and can easily be extended with new features where necessary. Currently Bambuser is using the Flash Media Server (FMS) for streaming the media, but it is license based and adds the extra cost to the company's budget. It does not support a wide range of platforms (e.g. OpenBSD and various Linux distributions) and also has limited options for the streaming. There is no real time monitoring and controlling functionality, which can show the status of essential services to the user, needed for the streaming (for example if the camera is working, microphone is turned on, battery power status. etc.).

In order to solve these issues the GStreamer is used, which is an Open source multimedia streaming framework. The GStreamer environment was tested on different Linux distributions. The research and implementation includes the creation of the streaming pipeline and analyzing which options (i.e. GStreamer elements and plugins) are required to stream the media. It also includes the testing of different pipeline parameters (for example video rate, audio rate etc.) and noting their effects in a real working environment. Python binding with GStreamer is used to have better control over the pipeline. Another requirement of this project was to add the functionality of monitoring and control that shows the status of essential services to the user. Implementation of this part is done by using server and client side coding. Further improvements and suggestions are also proposed in this report.

• 15.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Implementing a Resume Database with Online Learning to Rank2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

Learning to Rank is a research area within Machine Learning. It is mainly used in Information Retrieval and has been applied to, among other systems, web search engines and in computational advertising. The purpose of the Learning to Rank model is to rank a list of items, placing the most relevant at the top of the list, according to the users' requirements. Online Learning to Rank is a type of this model, that learns directly from the users' interactions with the system.

In this thesis a resume database is implemented, where the search engine applies an Online Learning to Rank algorithm, to rank consultant's resumes, when queries with required skills and competences are issued to the system. The implementation of the Resume Database and the ranking algorithm, as well as an evaluation, is presented in this report. Results from the evaluation indicates that the performance of the search engine, with the Online Learning to Rank algorithm, could be desirable in a production environment.

• 16.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Selection of foundational ontology for collaborative knowledge modeling in healthcare domain2010In: Artificial intelligence: methodology, systems, and applications / [ed] Dicheva, Darina; Dochev, Danail, Springer Berlin/Heidelberg, 2010, p. 261-262Conference paper (Refereed)

Ontology design is an important process for structuring knowledge to be reused in different projects in the health domain. In this paper, we describe an ontology design for the collaborative knowledge building system ACKTUS to be used for developing personalized knowledge applications for different domains. Different foundational ontologies were compared with respect to selected criteria considered vital for the project, such as modularity and descriptiveness.

• 17. Aichroth, Patrick
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
MICO - MEDIA IN CONTEXT2015In: 2015 IEEE International Conference on Multimedia & Expo Workshops (ICMEW), 2015Conference paper (Refereed)

The abundance of digital content requires cost-effective technologies to extract the hidden meaning from media objects. However, current approaches fail to deal with the challenges related to cross-media analysis, metadata publishing, querying and recommendation that are necessary to overcome this challenge. In this paper, we describe the EU project MICO (Media in Context) which aims to provide the necessary technologies based on open-source software (OSS) core components.

• 18.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
A Comparison of Rotation Parameterisations for Bundle Adjustment2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

Bundle Adjustment is an iterative process where 3D information is estimated from 2D image measurements. Typically, the position of object points are estimated simultaneously with the position and orientation of the cameras. While the object points and camera positions have a straightforward "natural" parameterisation, several possibilities exist for the rotation. In this thesis, seven parameterisation of the rotation were investigated; Euler angles (two variants), the Rodriguez representation, the axis-and-angle representation, unit quaternions, and two variants of the direction cosine matrix (DCM). The Euler and Rodriguez parameterisation are common in photogrammetry and each has three parameters. The other parameterisations have more parameters and one or more constraint between them.

The parameterisations were analyzed with respect to singularities, i.e. well-defined rotations that do not have any bounded and/or unique set of parameters. Four bundle adjustment experiments were setup, each corresponding to a singularity for one or more parameterisations. A fitth, singularity-free, experiment was also added. The experiments were perturbation studies that investigated the convergence properties of each parameterisation. The unconstrained parameterisations were solved by a damped and undamped Gauss-Newton algorithm, whereas the parameterisations with constraints were solved using damped and undamped algorithms based on the Gauss-Helmert estimation model.

As expected, the parameterisations corresponding to the constructed singularity had higher failure rates and required more iterations and execution time than the others when it did converge. Excluding their singular cases, the Euler xyz and Rodriguez representations were the fastest with about 37% of the dcm. Of the singularity-free parameterisation, the unit quaternion was the fastest with 79% of the dcm.

Surprisingly, the undamped bundle algorithms converged more often and faster than the damped bundle algorithms, even close to singularities. However, the undamped convergence was to a higher degree associated with numerical warnings and convergence toward angular values outside the nominal 2 range.

The results suggest that if singularities are not expected, the Euler xyz and Rodriguez representations are the best of the tested parameterisations. Otherwise, the unit quaternion is the best. As an alternative to the latter case, the switching algorithm by Singla may be used, at the expense of a more complex algorithm.

• 19.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Social Sciences, Department of Informatics.
Gestire-based Interaction and Implication for the Future2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis

Currently there exists an advanced and natural form of interaction, named gesture-based interaction. It has been applied in some fields successfully, especially in the form of game applications. Although people are filled with wonder at the new interaction, it has not replaced the traditional interaction, like keyboard and mouse. From the user experience point of view, gesture-based interaction has advantages which traditional interactive form cannot offer, but also shortcomings which people seem dissatisfied with. This thesis focuses on expressing user experience of gesture-based interaction by conducting interview method. Finally, this paper presents a new design and tries to find implications for its practical usage in the future.

• 20.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
The Thing about gaming experience2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

Despite the increasing popularity in the academic and practical fields of digital gaming, little has been explored and documented about gaming experience, especially firsthand account. This study uses Bruno Latour’s concept of the Thing while investigating digital gaming experience from frequent gamers’ standpoint using focus groups methodology. Additionally in-depth interviews were conducted with developers in order to gain a business perspective on the status of digital games development with regard to gamers. From the findings, Reality, Game, and Player were identified as agencies and their associations with the experiences of the gamers were gathered in making the Thing about gaming experience a matter of concern providing new meanings and further understandings of the abstract sets of experiences.

• 21.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Cell-phone Travel Planner GUI for SpaceTime2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

Global positioning systems have been having an increasing interest recently and been integrated and used in many applications to service positioning, navigation and travel planning. This project has set to design and test an interface of a travel planner for cell phones. A pre-study was made to investigate other travel planners to help the design of this application that has targeted a user friendly interface that people can use regardless of their background. A special feature, carpooling, has been introduced to ease the environmental, economical, and social aspects of navigation. The test was done as walk-through mockup images case scenarios. The test subjects were pleased with the interface’s friendliness, invoked carpooling issues, presented contradictory opinions regarding the interface's design, and offered future integration with other applications suggestions all of which were discussed. Overall, the test results were positive and few problems with the overall design were identified. A future study with more participants and a deeper analysis of the interface would be one way to further investigate the proposed interface.

• 22.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
The Glass Box Approach: Verifying Contextual Adherence to Values2019Conference paper (Refereed)

Artificial Intelligence (AI) applications are beingused to predict and assess behaviour in multiple domains, such as criminal justice and consumer finance, which directly affect human well-being. However, if AI is to be deployed safely, then people need to understand how the system is interpreting and whether it is adhering to the relevant moral values. Even though transparency is often seen as the requirement in this case, realistically it might notalways be possible or desirable, whereas the needto ensure that the system operates within set moral bounds remains.

In this paper, we present an approach to evaluate the moral bounds of an AI system based on the monitoring of its inputs and outputs. We place a ‘Glass Box’ around the system by mapping moral values into contextual verifiable norms that constrain inputs and outputs, in such a way that if these remain within the box we can guarantee that the system adheres to the value(s) in a specific context. The focus on inputs and outputs allows for the verification and comparison of vastly different intelligent systems–from deep neural networks to agent-based systems–whereas by making the context explicit we exposethe different perspectives and frameworks that are taken into account when subsuming moral values into specific norms and functionalities. We present a modal logic formalisation of the Glass Box approach which is domain-agnostic, implementable, and expandable.

• 23.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
An evaluation of HTML5 components for web-based manipulation of tabular data2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

HTML5 is a promising technology that is on its way to becoming a standard for the web. Companies that have built their web application components using plugins now have to move to a entirely new JavaScript environment. One such component is data grids or tables and will be the focus of this report.

In this report I present a proposal for evaluation criteria for tabular components in JavaScript frameworks. Using these criteria, grid components in some of the market leading frameworks are evaluated. Further I will for one of these frameworks present a test implementation and performance test focusing on load time with and without UI Virtualization.

• 24.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
An analysis of Mutation testing and Code coverage during progress of projects2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

In order to deliver high quality software projects, a developing team probably needs a well-developed test suite. There are several methods that aim to evaluate test suites in some way, such as Code coverage and Mutation testing. Code coverage describes the degree of source code that a program executes when running a test suite. Mutation testing measures the test suite effectiveness.

More development teams use code coverage to a greater extent than mutation testing. With code coverage being monitored throughout a project, could the development team risk drop of the test suite effectiveness as the codebase getting bigger with each version?

In this thesis, a mutation testing tool called PIT is used during progress of four well known open source projects. The reason for this is to show that mutation testing is an important technique to ensure continuously high test suite effectiveness, and does not only rely on code coverage measurements. In general, all projects perform well in both code coverage and test suite effectiveness, with the exception of one project inwhich the test suite effectiveness drops drastically. This drop shows that all projects are at risk of low test suite effectiveness, by not using mutation testing techniques.

• 25.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
Visual tree detection for autonomous navigation in forest environment2008In: IEEE Intelligent Vehicles SymposiumConference Location: Eindhoven, NETHERLANDS, 2008, , p. 1144-1149p. 1144-1149Conference paper (Refereed)

This paper describes a classification based tree detection method for autonomous navigation of forest vehicles in forest environment. Fusion of color, and texture cues has been used to segment the image into tree trunk and background objects. The segmentation of images into tree trunk and background objects is a challenging task due to high variations of illumination, effect of different color shades, non-homogeneous bark texture, shadows and foreshortening. To accomplish this, the approach has been to find the best combinations of color, and texture descriptors, and classification techniques. An additional task has been to estimate the distance between forest vehicle and the base of segmented trees using monocular vision. A simple heuristic distance measurement method is proposed that is based on pixel height and a reference width. The performance of various color and texture operators, and accuracy of classifiers has been evaluated using cross validation techniques.

• 26.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Capacity Scaling for Elastic Compute Clouds2013Licentiate thesis, comprehensive summary (Other academic)

• 27.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Nile University.
Optimizing Replica Placement in Peer-Assisted Cloud Stores2011Conference paper (Refereed)

Peer-assisted cloud storage systems use the unutilizedresources of the clients subscribed to a storage cloudto offload the servers of the cloud. The provider distributesdata replicas on the clients instead of replicating on the localinfrastructure. These replicas allow the provider to providea highly available, reliable and cheap service at a reducedcost. In this work we introduce NileStore, a protocol forreplication management in peer-assisted cloud storage. Theprotocol converts the replica placement problem into a lineartask assignment problem. We design five utility functionsto optimize placement taking into account the bandwidth,free storage and the size of data in need of replication oneach peer. The problem is solved using a suboptimal greedyoptimization algorithm. We show our simulation results usingthe different utilities under realistic network conditions. Ourresults show that using our approach offloads the cloud serversby about 90% compared to a random placement algorithmwhile consuming 98.5% less resources compared to a normalstorage cloud.

• 28.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Nile University.
Replica Placement in Peer-Assisted Clouds: An Economic Approach2011In: Lecture Notes in Computer Science / [ed] Pascal Felber, Romain Rouvoy, Springer, 2011, p. 208-213Conference paper (Refereed)

We introduce NileStore, a replica placement algorithm based on an economical model for use in Peer-assisted cloud storage. The algorithm uses storage and bandwidth resources of peers to offload the cloud provider’s resources. We formulate the placement problem as a linear task assignment problem where the aim is to minimize time needed for file replicas to reach a certain desired threshold. Using simulation, We reduce the probability of a file being served from the provider’s servers by more than 97.5% under realistic network conditions.

• 29.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Which Cloud Auto-Scaler Should I Use for my Application?: Benchmarking Auto-Scaling Algorithms2016In: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), Association for Computing Machinery (ACM), 2016, p. 131-132Conference paper (Refereed)
• 30.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Lund University. Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
Analysis and characterization of a Video-on-Demand service workload2015In: Proceedings of the 6th ACM Multimedia Systems Conference, MMSys 2015, ACM Digital Library, 2015, p. 189-200Conference paper (Refereed)

Video-on-Demand (VoD) and video sharing services accountfor a large percentage of the total downstream Internet traf-fic. In order to provide a better understanding of the loadon these services, we analyze and model a workload tracefrom a VoD service provided by a major Swedish TV broad-caster. The trace contains over half a million requests gener-ated by more than 20000 unique users. Among other things,we study the request arrival rate, the inter-arrival time, thespikes in the workload, the video popularity distribution, thestreaming bit-rate distribution and the video duration distri-bution. Our results show that the user and the session ar-rival rates for the TV4 workload does not follow a Poissonprocess. The arrival rate distribution is modeled using a log-normal distribution while the inter-arrival time distributionis modeled using a stretched exponential distribution. Weobserve the “impatient user” behavior where users abandonstreaming sessions after minutes or even seconds of startingthem. Both very popular videos and non-popular videos areparticularly affected by impatient users. We investigate ifthis behavior is an invariant for VoD workloads.

• 31.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Dept. of Electrical and Information Technology, Lund University, Lund, Sweden. Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
Efficient provisioning of bursty scientific workloads on the cloud using adaptive elasticity control2012In: Proceedings of the 3rd workshop on Scientific Cloud Computing Date, Association for Computing Machinery (ACM), 2012, p. 31-40Conference paper (Refereed)

Elasticity is the ability of a cloud infrastructure to dynamically change theamount of resources allocated to a running service as load changes. We build anautonomous elasticity controller that changes the number of virtual machinesallocated to a service based on both monitored load changes and predictions offuture load. The cloud infrastructure is modeled as a G/G/N queue. This modelis used to construct a hybrid reactive-adaptive controller that quickly reactsto sudden load changes, prevents premature release of resources, takes intoaccount the heterogeneity of the workload, and avoids oscillations. Using simulations with Web and cluster workload traces, we show that our proposed controller lowers the number of delayed requests by a factor of 70 for the Web traces and 3 for the cluster traces when compared to a reactive controller. Ourcontroller also decreases the average number of queued requests by a factor of 3 for both traces, and reduces oscillations by a factor of 7 for the Web traces and 3 for the cluster traces. This comes at the expense of between 20% and 30% over-provisioning, as compared to a few percent for the reactive controller.

• 32.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
How will your workload look like in 6 years?: Analyzing Wikimedia's workload2014In: Proceedings of the 2014 IEEE International Conference on Cloud Engineering (IC2E 2014) / [ed] Lisa O’Conner, IEEE Computer Society, 2014, p. 349-354Conference paper (Refereed)

Accurate understanding of workloads is key to efficient cloud resource management as well as to the design of large-scale applications. We analyze and model the workload of Wikipedia, one of the world's largest web sites. With descriptive statistics, time-series analysis, and polynomial splines, we study the trend and seasonality of the workload, its evolution over the years, and also investigate patterns in page popularity. Our results indicate that the workload is highly predictable with a strong seasonality. Our short term prediction algorithm is able to predict the workload with a Mean Absolute Percentage Error of around 2%.

• 33.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
Measuring cloud workload burstiness2014In: 2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing (UCC), IEEE conference proceedings, 2014, p. 566-572Conference paper (Refereed)

Workload burstiness and spikes are among the main reasons for service disruptions and decrease in the Quality-of-Service (QoS) of online services. They are hurdles that complicate autonomic resource management of datacenters. In this paper, we review the state-of-the-art in online identification of workload spikes and quantifying burstiness. The applicability of some of the proposed techniques is examined for Cloud systems where various workloads are co-hosted on the same platform. We discuss Sample Entropy (SampEn), a measure used in biomedical signal analysis, as a potential measure for burstiness. A modification to the original measure is introduced to make it more suitable for Cloud workloads.

• 34.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science.
An adaptive hybrid elasticity controller for cloud infrastructures2012In: 2012 IEEE Network operations and managent symposium (NOMS), IEEE Communications Society, 2012, p. 204-212Conference paper (Refereed)

Cloud elasticity is the ability of the cloud infrastructure to rapidly change the amount of resources allocated to a service in order to meet the actual varying demands on the service while enforcing SLAs. In this paper, we focus on horizontal elasticity, the ability of the infrastructure to add or remove virtual machines allocated to a service deployed in the cloud. We model a cloud service using queuing theory. Using that model we build two adaptive proactive controllers that estimate the future load on a service. We explore the different possible scenarios for deploying a proactive elasticity controller coupled with a reactive elasticity controller in the cloud. Using simulation with workload traces from the FIFA world-cup web servers, we show that a hybrid controller that incorporates a reactive controller for scale up coupled with our proactive controllers for scale down decisions reduces SLA violations by a factor of 2 to 10 compared to a regression based controller or a completely reactive controller.

• 35.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science. Lund University.
WAC: A Workload analysis and classification tool for automatic selection of cloud auto-scaling methodsManuscript (preprint) (Other academic)

• 36.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of Electrical and Information Technology, Lund University, Lund, Sweden.

Elasticity algorithms for cloud infrastructures dynamically change the amount of resources allocated to a running service according to the current and predicted future load. Since there is no perfect predictor, and since different applications’ workloads have different characteristics, no single elasticity algorithm is suitable for future predictions for all workloads. In this work, we introduceWAC, aWorkload Analysis and Classification tool that analyzes workloads and assigns them to the most suitable elasticity controllers based on the workloads’ characteristics and a set of business level objectives.

• 37.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Workload characterization, controller design and performance evaluation for cloud capacity autoscaling2015Doctoral thesis, comprehensive summary (Other academic)

• 38.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Object Tracking withIphone 3Gs2010Independent thesis Advanced level (degree of Master (One Year)), 30 credits / 45 HE creditsStudent thesis

In June of 2007 Apple Inc. released the smartphone Iphone. It was a groundbreaking success that set a new standard for what a smartphone should be able to do. Apple has improved the Iphone every year since then and the 3Gs is the newest Iphone model. As the phones have improved, both when looking at hardware and software, the applications have improved as well. The Iphone 3Gs provides the possibility to use the camera as an application background and with that the possibility to analyze the surroundings, making it possible to track objects that the phone is pointed towards.This thesis examines how object tracking can be implemented in applications for Iphone 3Gs as well as providing a survey of four different areas of use that have been implemented in Xcode: an augmented reality car game, a letter tracking application, a face recognition application and an object recognition application.

• 39.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
En jämförelsestudie av JavaScript-bibliotek Med fokus på mjukvarukvalitet2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

JavaScripts popularity is increasing and the number of libraries too. This report focuses on well-known software metrics in complexity, maintainability and different size-metrics. A few different JavaScript libraries are compared and analyzed. The result shows that there are indeed differences, mostly in size- and complexity-measures where some functions are implemented with a higher complexity.

• 40.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
A Comparison Between MongoDB and MySQL Document Store Considering Performance2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

Databases are an important part of today’s applications where data has to be stored and accessed quickly. One of the important criteria when choosing what database technology to use is performance, where you want the operations to be as fast as possible.

In April 2016 Oracle released a alternative way of working with MySQL as a document store. This creates an opportunity to compare it to MongoDB which is one of the most popular document store databases.

The comparison was performed by testing different operations on the databases and comparing the resulting time it took.

The result showed that MongoDB was faster in every test case for every operation.

• 41.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Classification of Heart Sounds with Deep Learning2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

Health care is becoming more and more digitalized and examinations of patients from a distance are closer to reality than fiction. One of these examinations would be to automatically classify a patient-recorded audiosegment of its heartbeats as healthy or pathological. This thesis examines how it can be achieved by examining different kinds of neural networks; convolutional neural networks (CNN) and long short-term memory networks (LSTM). The theory of artificial neural networks is explained. With this foundation, the feed forward CNN and the recurrent LSTM-network have their methods described. Before these methods can be used, the required pre-processing has to be completed, which is different for the two types of networks. Using this theory, the process of how to implement the networks in Matlab is explained. Different CNN:s are compared to each other, then the best performing CNN is compared to the LSTM-network. When comparing the two different networks to each other, cross validation is used to achieve the most correct result possible. The networks are compared by accuracy, least amount of training time and least amount of training data. A final resulti s presented, to show which type of network has the best performance, together with a discussion to explain the results. The CNN performed better than the LSTM-network in all aspects. A reflection on what could have been done differently to achieve a better result is posted.

• 42.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
School Timetabling in Theory and Practice A comparative study of Simulated Annealing and Tabu Search2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

School timetabling is way of distributing resources such as teachers and classrooms over a fixed period of time. This task can be difficult and very time-consuming. If the process of generating timetables is automated with the help of algorithms then this can help save both time and money for the educational institute.

In this thesis a general timetable is presented along with a set of constraints commonly used in school timetabling. Two meta heuristic algorithms with previous satisfying results, Simulated Annealing and Tabu Search, are implemented and benchmarked against each other in order to evaluate the performance of these.

The results show that although both algorithms are good candidates for creating timetables, Simulated Annealing has the edge both in run time and the quality of the timetable.

• 43.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Natural Language Processing In A Distributed  Environment: A comparative performance analysis of Apache Spark and Hadoop MapReduce2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

A big majority of the data hosted on the internet today is in natural text and therefore understanding natural language and how to effectively process and analyzing text has become a big part of data mining. Natural Language Processing has many applications in fields such as business intelligence and security purposes.The problem with natural language text processing and analyzing is the computational power needed to perform the actual processing, performance of personal computer has not kept up with amounts of data that needs to be processed so another approach with good performance scaling potential is needed.This study does a preliminary comparative performance analysis of processing natural language text in an distributed environment using two popular open-source frameworks, Hadoop MapReduce and Apache Spark.

• 44.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
An Experimental Evaluation of PIT’s Mutation Operators2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

Mutation testing is a fault-finding software testing technique that creates mutants by injecting a syntactic change into the source code. This technique operates by evaluating the ability of a testsuite to detect mutants, which is used to asses the quality of a test suite. The information from mutation testing can be used to improve the quality of a test suite by developing additional test cases. It is a promising technique, but the expensive nature of mutation testing has prevented its wide spread, practical use.

One approach to make mutation testing more efficient is selective mutation testing. This approach proposes to use a subset of the available mutation operators, thereby reducing the number of mutants generated which will lead to a reduced execution time.

According to theory many mutants are redundant and do not provide any useful information in the development of additional test cases. This study will evaluate PIT, a mutation testing tool, by using selective mutation testing on five programs, and compare the effectiveness of PIT with MuJava. The results showed that PIT’s default operators generated a small and effective set of mutants and at the same time giving a satisfying mutation score.

However, there was no significant difference in mutation score produced by the different sets of operators. The test suites adequate for PIT managed to detect 75-85% of MuJava’s mutants, which is relatively good when taken into consideration that PIT generated less than half as many mutants.

• 45.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Threat, risk, and vulnerabilityanalyses during the developmentof IT systems in the SwedishArmed Forces2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

This master’s thesis describes how two models from the Swedish Armed Forces; the risk management model and the IT lifecycle model can be combined. An example is then presented for how the risk management model can be extended for threats, risks, and vulnerabilities related to information technology. The combination and extension of the models are based on a literature study that lists and compares models and methods for threat, risk, andvulnerability analyses, as well as an analysis of threats related to information technology. From the combined and extended model, a design proposal for how to implement the identified functionality was identified. Based on an evaluation that showed that the program NTE and the plugin EASTER were suitable as the foundation for this implementation, the program NTE and the plugin EASTER were extended with further functionality and resulted in the implementation of the plugin ASCENSION. This was evaluated and resulted in ideas for a possible re-design and examples of the future potential of ASCENSION.

• 46.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North). Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North). Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North).
Parallel Algorithms for Triangular Periodic Sylvester-Type Matrix Equations2008In: Euro-Par 2008 - Parallel Processing: 14th International Euro-Par Conference Conference Location: Las Palmas de Gran Canaria, SPAIN, Springer , 2008, p. 780-789Conference paper (Refereed)

We present parallel algorithms for triangular periodic Sylvester-type matrix equations, conceptually being the third step of a periodic Bartels-Stewart-like solution method for general periodic Sylvester-type matrix equations based on variants of the periodic Schur decomposition. The presented algorithms are designed and implemented in the framework of the recently developed HPG library SCASY and are based on explicit blocking, 2-dimensional block cyclic data distribution and a wavefront-like traversal of the right hand side matrices. High performance is obtained by rich usage of level 3 BLAS operations. It is also demonstrated how several important key concepts of SCASY regarding communications and the treatment of quasi-triangular coefficient matrices are generalized to the periodic case. Some experimental results from a distributed memory Linux cluster demonstrate are also presented.

• 47.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Model based object finding in occluded cluttered environments2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

The aim of the thesis is object finding in occluded and cluttered environment using computer vision techniques and robot motion. Difficulties of the object finding are 1. finding objects at hidden area and 2. finding unrecognized objects. For solving the difficulties, two methods were developed, one is for finding objects in occluded cluttered environments using model based object finding and the other to increase the robustness in object finding by identifying known objects that are unidentified. The goal was to search occluded areas with the bumblebee2 stereo camera to be able to identify all known objects in the environment by removing all visible known objects To identify known objects SURF [9] was used and to be able to remove the identified objects their location first needed to be localized. To localize the object‘s x and y coordinate the information from SURF [9] was used, and the distance coordinate z is calculated using the depth image from the stereo camera. The method to identify objects the SURF [9] algorithm had missed to identify uses a method to find unknown segments in the environment. By using a push motion on the segments to change their angle it can remove possible light reflections and the object can be identified. The results of this research show that the method can find objects in occluded cluttered areas and it can also identified missed known objects.

• 48.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Pseudo-optimal strategies in no-limit poker2006In: ICGA Journal, ISSN 1389-6911, Vol. 29, no 3, p. 143-149Article in journal (Refereed)

Games have always been a strong driving force in Artificial Intelligence. In the last ten years huge improvements has been made in perfect information games like chess and Othello. The strongest computer agents can nowadays beat the strongest human players. This is not the case for imperfect information games such as poker and bridge where creating an expert computer player has shown to be much harder. Previous research in poker has either addressed limit poker or simplified variations of poker games. This paper tries to extend known techniques successfully used in limit poker to no-limit. No-limit poker increases the size of the game tree drastically. To reduce the complexity an abstracted model of the game is created. Finding an optimal strategy for the new model is now a minimization problem using linear programming techniques. The result is a set of pseudo-optimal strategies for no-limit Texas Hold'em. A bot named AGGROBOT was built from these strategies which perform well as long as the players' stack sizes are fairly small.

• 49.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Influence of File Systems on Performance When Working with an Abundance of Small Files2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis

High-performance computing is widely used within the scientific community to perform demanding computational work. Using the resources available at a high-performance center in an efficient manner is of great importance. One potential bottleneck for high-performance computing is file systems.

In this study two different file systems, the Lustre file system and MATLAB Datastore, have been evaluated in terms of performance when performing computations on an abundance of small files. The performance test consisted of classification of large numbers of small (<2 megabytes) images in MATLAB using the high-performance computer system Kebnekaise at HPC2N in Umeå.

Results indicate that MATLAB Datastore gives better performance than the Lustre file system for all images sets tested in the study. This makes it possible to recommend using MATLAB Datastore over the Lustre file system in situations where large number of smaller files are to be read and from the file system.

• 50.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Large Scale Server Publishing for Dynamic Content2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

The number of interactive and dynamic web services on the Internet is growing more and more and to accommodate as much functionality as possible, many techniques for asynchronous web communication are being developed. This thesis report describes the evaluation of an existing web service that uses bidirectional communication over the web to provide voting functionality in real-time on web pages. The thesis consists of an assessment of problem domains, an evaluation of the system and an implementation of some of the identified problems. It focuses on a few core issues of the current solution, namely the communication techniques between the client and the server, the setup of the overarching structure of the system and the separation of messaging channels for different use cases.The evaluation of the reference system was motivated by addressing the issue of being able to packet the service better as a product and create a distinction between the use case and the underlying system. It was done so that the stakeholders of the product may more easily define the way the service can be used and so that a better course of action can be taken for continuing the development of the service. The implemented solution shows an example of how the messaging channels could be separated and what kind of trade-os exist between the current and implemented solution.

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