Notas sobre actualidad relacionada con mis asignaturas y mi trabajo en la Universidad.
Se acaba de publicar el primer número de 2015 de ReVisión, la revista de la Asociación de Enseñantes Universitarios de la Informática.
Creating rankings might seem like a vain exercise in belly-button gazing, even more so for people so unlike that kind of things as programmers. However, in this paper we will try to prove how creating city (or province) based on rankings in Spain has led to all kinds of interesting effects, including increased productivity and community building.
El día 8 de septiembre era el día Día Internacional de la Alfabetización y del gabinete de prensa de la universidad me dijeron que los de la televisión querían hacer un reportaje sobre analfabetismo digital.
Petri nets are graph based tools to model and study concurrent systems and their properties; one of them is liveness, which is related to the possibility of every part of the system to be activated eventually. Siphons are sets of places that are related to liveness properties. When we need to deal with realistic problems its computation is hard or even impossible and this is why in this paper we are approaching it using evolutionary computation, a meta-heuristic that has proved it can successfully find solutions when the search space is big. In a previous work a formulation of the siphon property based on linear constraints and a genetic algorithm was proposed for general Petri Nets. Here we propose to adapt an algebraic method based on the selection of rows of the matrix that cancel in an adequate way input and output transitions so the resulting selection is a siphon. We will also present an evaluation for a family of resource allocation systems (RAS). The proposed solution is based on a genetic algorithm (GA); we can see how siphons can be computed using this genetic algorithm, with experiments showing that in some cases they are able to find a few solutions in less time than previous deterministic algorithms.It will appear soon in my Research Interests page, but if you can wait for a copy, just drop me an email.
Deaddlock states are undesirable situations in any system. Their avoiding presents a major issue in control of resource allocation systems (RAS), a theoretical paradigm used in construction of several application systems, including flexible manufacturing systems. In coordinating RAS with non-sequential processes, i.e. processes containing concurrent execution in their development, it has been proved that deadlock avoidance policies developed for sequential systems are applicable. This requires, however, transformation of the coordinating RAS structure using reachability graph of single processes to a sequential RAS, what brings the exponential growth of the modelled system size.
In this paper, we present a deadlock avoidance method that allows using the original system, coordinating RAS with non-sequential processes, with additional data structures calculated before the system start. It is a banker's like approach -- an enhanced version of the banker's algorithm with our proposed data structures manipulation.
The disparity of Petri net models in the literature for the study of resource allocation problems in Flexible Manufacturing Systems (FMSs) is overwhelming. Paradoxically, those models often strongly overlap in terms of their modeling capability. Such clustering seems to be impelled by a mature knowledge of results which capsize liveness at the topological level of the FMS for families of models which comply with some properties of good behaviour. Not rarely, such properties are embraced at the expense of severe or inconsistent syntax restrictions paying slight regard to actual modelling requirements in the application domain of FMSs. In this paper, we promote a distillation of the current amalgam of subclasses and tangent results, proposing taxonomic categories that allow capturing the different capabilities of each kind of model and establishing a reference framework for past and future advances.
Se acaba de publicar el segundo número de 2014 de ReVisión, la revista de la Asociación de Enseñantes Universitarios de la Informática.