Fundamenta Informaticae - Volume 179, issue 1

Authors: Benouhiba, Toufik

Article Type: Research Article

Abstract: Probabilistic models play an important role in many fields such as distributed systems and simulations. Like non-probabilistic systems, they can be synthesized using classical refinement-based techniques, but they also require identifying the probability distributions to be used and their parameters. Since a fully automated and blind refinement is generally undecidable, many works tried to synthesize them by looking for the parameters of the distributions. Syntax-guided synthesizing approaches are more powerful, they try to synthesize models structurally by using context-free grammars. However, many problems arise like huge search space, the complexity of generated models, and the limitation of context-free grammars to …define constraints over the structure. In this paper, we propose a multi-step refinement approach, based on meta-models, offering several abstraction levels to reduce the size of the search space. More specifically, each refinement step is divided into two stages in which the desired shape of models is first described by context-sensitive constraints. In the second stage, model templates are instantiated by using global optimization techniques. We use our approach to a synthesize a set of optimal probabilistic models and show that context-sensitive constraints coupled with the multi-level abilities of the approach make the synthesis task more effective. Show more

Keywords: model synthesis, refinement, search-based software engineering, constraint satisfaction, probabilistic model checking

DOI: 10.3233/FI-2021-2011

Citation: Fundamenta Informaticae, vol. 179, no. 1, pp. 1-33, 2021

Authors: Marrakchi, Sirine | Jemni, Mohamed

Article Type: Research Article

Abstract: A new approach for solving triangular band linear systems is established in this study to balance the load and obtain a high degree of parallelism. Our investigation consists to attribute both adequate start time and processor to each task and eliminate the useless dependencies which are not used in the parallel solve stage. Thereby, processors execute in parallel their related tasks taking account of the considered precedence constraints. The theoretical lower bounds for parallel execution time and the number of processors required to carry out the task graph in the shortest time are determined. Experimentations are realized on a shared-memory …multicore processor. The experimental results are fitted to the values derived from the determined mathematical formulas. The comparison of results obtained by our contribution with those from triangular systems resolution routine belonging to the library PLASMA, Parallel Linear Algebra Software for Multicore Architectures, confirms the efficiency of the proposed approach. Show more

Keywords: Solving triangular band linear systems, Parallel execution time, Load balancing, Precedence graph, Shared-memory multicore processor

DOI: 10.3233/FI-2021-2012

Citation: Fundamenta Informaticae, vol. 179, no. 1, pp. 35-58, 2021

Authors: Šlapal, Josef

Article Type: Research Article

Abstract: In this paper, we propose new definitions of digital Jordan curves and digital Jordan surfaces. We start with introducing and studying closure operators on a given set that are associated with n -ary relations (n > 1 an integer) on this set. Discussed are in particular the closure operators associated with certain n -ary relations on the digital line ℤ. Of these relations, we focus on a ternary one equipping the digital plane ℤ2 and the digital space ℤ3 with the closure operator associated with the direct product of two and three, respectively, copies of this ternary …relation. The connectedness provided by the closure operator is shown to be suitable for defining digital curves satisfying a digital Jordan curve theorem and digital surfaces satisfying a digital Jordan surface theorem. Show more

Keywords: Digital space, n-ary relation, closure operator, connectedness, digital Jordan curve, digital Jordan surface

DOI: 10.3233/FI-2021-2013

Citation: Fundamenta Informaticae, vol. 179, no. 1, pp. 59-74, 2021

Authors: Syau, Yu-Ru | Liau, Churn-Jung | Lin, En-Bing

Article Type: Research Article

Abstract: We present variable precision generalized rough set approach to characterize incomplete decision tables. We show how to determine the discernibility threshold for a reflexive relational decision system in the variable precision generalized rough set model. We also point out some properties of positive regions and prove a statement of the necessary condition for weak consistency of an incomplete decision table. We present two examples to illustrate the results obtained in this paper.

Keywords: Rough sets, variable precision rough set models, incomplete decision tables, consistency, relative discernibility

DOI: 10.3233/FI-2021-2014

Citation: Fundamenta Informaticae, vol. 179, no. 1, pp. 75-92, 2021