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Walter B.,Poznan University of Technology | Alkhaeir T.,Poznan Supercomputing and Networking Center
Information and Software Technology | Year: 2016

Context - Design patterns represent recommended generic solutions to various design problems, whereas code smells are symptoms of design issues that could hinder further maintenance of a software system. We can intuitively expect that both concepts are mutually exclusive, and the presence of patterns is correlated with the absence of code smells. However, the existing experimental evidence supporting this claim is still insufficient, and studies separately analyzing the impact of smells and patterns on code quality deliver diverse results. Objective - The aim of the paper is threefold: (1) to determine if and how the presence of the design patterns is linked to the presence of code smells, (2) to investigate if and how these relationships change throughout evolution of code, and (3) to identify the relationships between individual patterns and code smells. Method - We analyze nine design patterns and seven code smells in two medium-size, long-evolving, open source Java systems. In particular, we explore how the presence of design patterns impacts the presence of code smells, analyze if this link evolves over time, and extract association rules that describe their individual relationships. Results - Classes participating in design patterns appear to display code smells less frequently than other classes. The observed effect is stronger for some patterns (e.g., Singleton, State-Strategy) and weaker for others (e.g., Composite). The ratio between the relative number of smells in the classes participating in patterns and the relative number of smells in other classes, is approximately stable or slightly decreasing in time. Conclusion - This observation could be used to anticipate the smell-proneness of individual classes, and improve code smell detectors. Overall, our findings indicate that the presence of design patterns is linked with a lower number of code smell instances. This could support programmers in a context-sensitive analysis of smells in code. © 2016 Elsevier B.V. All rights reserved.

Kowalik K.,Nicolaus Copernicus University | Hanasz M.,Nicolaus Copernicus University | Woltanski D.,Nicolaus Copernicus University | Gawryszczak A.,Poznan Supercomputing and Networking Center
Monthly Notices of the Royal Astronomical Society | Year: 2013

We investigate streaming instability using two-fluid approximation (neutral gas and dust) in a quasi-global, unstratified protoplanetary disc, with the help of PIERNIK code. We compare amplification rate of the eigenmode in numerical simulations, with the corresponding growth resulting from the linear stability analysis of full system of Euler's equation including aerodynamic drag. Following Youdin & Goodman (2005), we show that (1) rapid dust clumping occurs due to the difference in azimuthal velocities of gas and dust, coupled by the drag force, (2) initial density perturbations are amplified by several orders of magnitude. We demonstrate that the multifluid extension of the simple and efficient Relaxing TVD scheme, implemented in PIERNIK, leads to results, which are compatible with those obtained with other methods. ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Palma R.,Ontology Engineering Group | Palma R.,Poznan Supercomputing and Networking Center | Corcho O.,Ontology Engineering Group | Gomez-Perez A.,Ontology Engineering Group | And 2 more authors.
Journal of Web Semantics | Year: 2011

This paper describes our methodological and technological approach for collaborative ontology development in inter-organizational settings. It is based on the formalization of the collaborative ontology development process by means of an explicit editorial workflow, which coordinates proposals for changes among ontology editors in a flexible manner. This approach is supported by new models, methods and strategies for ontology change management in distributed environments: we propose a new form of ontology change representation, organized in layers so as to provide as much independence as possible from the underlying ontology languages, together with methods and strategies for their manipulation, version management, capture, storage and maintenance, some of which are based on existing proposals in the state of the art. Moreover, we propose a set of change propagation strategies that allow keeping distributed copies of the same ontology synchronized. Finally, we illustrate and evaluate our approach with a test case in the fishery domain from the United Nations Food and Agriculture Organisation (FAO). The preliminary results obtained from our evaluation suggest positive indication on the practical value and usability of the work here presented. © 2011 Elsevier B.V. All rights reserved.

Olejnik L.,CERN | Olejnik L.,Poznan Supercomputing and Networking Center
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We propose a quantum solution to the classical private information retrieval (PIR) problem, which allows one to query a database in a private manner. The protocol offers privacy thresholds and allows the user to obtain information from a database in a way that offers the potential adversary, in this model the database owner, no possibility of deterministically establishing the query contents. This protocol may also be viewed as a solution to the symmetrically private information retrieval problem in that it can offer database security (inability for a querying user to steal its contents). Compared to classical solutions, the protocol offers substantial improvement in terms of communication complexity. In comparison with the recent quantum private queries protocol, it is more efficient in terms of communication complexity and the number of rounds, while offering a clear privacy parameter. We discuss the security of the protocol and analyze its strengths and conclude that using this technique makes it challenging to obtain the unconditional (in the information-theoretic sense) privacy degree; nevertheless, in addition to being simple, the protocol still offers a privacy level. The oracle used in the protocol is inspired both by the classical computational PIR solutions as well as the Deutsch-Jozsa oracle. © 2011 American Physical Society.

Piatek W.,Poznan Supercomputing and Networking Center
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

The focus of this paper is a Data Center Workload and Resource Management Simulator (DCworms) which enables modeling and simulation of data centers to estimate their performance, energy consumption, and energy-efficiency metrics for diverse workloads and management policies. We present its functionality in terms of energy-efficiency modeling and methods of power usage estimations available in the simulator. Moreover, we show an application of DCworms within the CoolEmAll project that addresses the important problem of data center energy efficiency. © 2013 Springer-Verlag.

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