| 1. |
- Edlund, Åke, et al.
(författare)
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Practical Cloud Evaluation from a Nordic eScience User perspective
- 2011
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Ingår i: Proceedings of the 5th international workshop on Virtualization technologies in distributed computing. - New York, NY, USA : ACM.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we describe the findings of the NEON project - a cross-Nordic - Sweden, Norway, Denmark, Finland and Iceland - project evaluating the usefulness of private versus public cloud services for HPC users. Our findings are briefly that private cloud technology is not mature enough yet to provide a transparent user experience. It is expected that this will be the case mid 2012. The cost efficiency of both public and private cloud should be continuously monitored as there is a strong downward trend. This conclusion is supported by NEON experimenting as well as larger initiatives e.g. StratusLab reports. Public cloud technology is mature enough but lacks certain features that will be necessary to include cloud resources in a transparent manner in a national infrastructure like the Norwegian NOTUR (www.notur.no) case, e.g. with respect to quota management. These features are expected to emerge in 2011 via third party management software and in the best of breed public cloud services. Public clouds are competitive in the low end for non-HPC jobs (low memory, low number of cores) on price. A significant fraction (ca. 20%) of the jobs running on the current Nordic supercomputer infrastructure are potentially suitable for cloud-like technology. This holds in particular for singlethreaded or single-node jobs with small/medium memory requirements and non-intensive I/O. There is a backlog of real supercomputer jobs that suffers from the non-HPC jobs on the supercomputer infrastructure. Off-loading these non-HPC jobs to a public cloud would effectively add supercomputing capacity. Another finding is that available storage capacity is not accessible in a user-friendly way; most storage clouds are only accessible via programmable interfaces. A number of experiments and piloting are presented to support these claims.
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| 2. |
- Hvannberg, Ebba Thora, et al.
(författare)
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Heuristic evaluation : Comparing ways of finding and reporting usability problems
- 2007
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Ingår i: Interacting with computers. - : Oxford University Press (OUP). - 0953-5438 .- 1873-7951. ; 19:2, s. 225-240
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Tidskriftsartikel (refereegranskat)abstract
- Research on heuristic evaluation in recent years has focused on improving its effectiveness and efficiency with respect to user testing. The aim of this paper is to refine a research agenda for comparing and contrasting evaluation methods. To reach this goal, a framework is presented to evaluate the effectiveness of different types of support for structured usability problem reporting. This paper reports on an empirical study of this framework that compares two sets of heuristics, Nielsen's heuristics and the cognitive principles of Gerhardt-Powals, and. two media of reporting a usability problem, i.e. either using a web tool or paper. The study found that there were no significant differences between any of the four groups in effectiveness, efficiency and inter-evaluator reliability. A more significant contribution of this research is that the framework used for the experiments proved successful and should be reusable by other researchers because of its thorough structure.
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| 3. |
- Klamma, Rolf, et al.
(författare)
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Social software for life-long learning
- 2007
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Ingår i: Educational Technology & Society. - MASSEY UNIVERSITY, Palmerston North, New Zealand : IEEE Computer Society. - 1176-3647 .- 1436-4522. ; 10:3, s. 72-83
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Tidskriftsartikel (refereegranskat)abstract
- Life-long learning is a key issue for our knowledge society. With social software systems new heterogeneous kinds of technology enhanced informal learning are now available to the life-long learner. Learners outside of learning institutions now have access to powerful social communities of experts and peers who are together forging a new web 2.0. This paper reviews current work in pan-European initiatives that impact upon life-long learning via views of professional learning, learner competence and social networking. It seeks to provide an overview of some of the critical research questions for the interdisciplinary field of social software research.
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| 4. |
- Klamma, Rolf, et al.
(författare)
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Social Software for Professional Learning : Examples and Research Issues
- 2006
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Ingår i: Proceedings - Sixth International Conference on Advanced Learning Technologies, ICALT 2006. - 0769526322 ; , s. 912-915
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Konferensbidrag (refereegranskat)abstract
- Social software is used widely in organizational knowledge management and professional learning. The PROLEARN network of excellence appreciates the trend of lowering the barriers between knowledge and learning management strategies for organizations and individuals. But, companies should not underestimate the needs for systematic support based on sound theories and technologies. We illustrate the requirements by examples and research issues for collaborative adaptive learning platforms for workplace learning in organizations
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| 5. |
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| 6. |
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| 7. |
- Källén, Malin, et al.
(författare)
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Impact of Code Refactoring using Object-Oriented Methodology on a Scientific Computing Application
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The effect of refactoring on the quality of software has been extensively evaluated in scientific studies. We see a need to also consider its effect on performance. To this end, we have refactored the central parts of a code base developed in academia for a class of computationally demanding scientific computing problems. We made design choices based on the SOLID principles and we used object-oriented techniques in the implementation. We discuss the effect on maintainability qualitatively and also analyze it quantitatively. Not surprisingly, we find that maintainability increased as an effect of the refactoring. We also find that dynamic binding in the most frequently executed parts of the code makes the execution times increase significantly. By exploiting static polymorphism, we reduce the increase in execution times, and in some cases even get better performance than for the original code. We argue that the code version implementing static polymorphism is less maintainable than the one using dynamic polymorphism, although both versions are considerably more maintainable than the original code. Accordingly, we conclude that static polymorphism could be used to increase maintainability for performance critical code bases. Last, we argue that static polymorphism could even improve performance in some procedural code bases.
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