Reports de recerca
http://hdl.handle.net/2117/3094
2016-05-29T04:07:03ZA review on DISC 2005, the 19th International Symposium on Distributed Computing
http://hdl.handle.net/2117/87343
A review on DISC 2005, the 19th International Symposium on Distributed Computing
Blesa Aguilera, Maria Josep; Georgiou, Chryssis
DISC is an international symposium on the theory, design, analysis, implementation and application of distributed systems and networks. The well-known International Symposium on Distributed Computing is organized annually in cooperation with the European Association for Theoretical Computer Science (EATCS). This is a review on the 19th International Symposium on Distributed Computing, which took place in Kraków, Poland, on September 26--29, 2005. The proceedings of DISC 2005 are published by Springer, as volume 3724 of the Lecture Notes in Computer Science (LNCS) series. The conference website can be found at www.mimuw.edu.pl/~disc2005.
2016-05-26T08:10:28ZBlesa Aguilera, Maria JosepGeorgiou, ChryssisDISC is an international symposium on the theory, design, analysis, implementation and application of distributed systems and networks. The well-known International Symposium on Distributed Computing is organized annually in cooperation with the European Association for Theoretical Computer Science (EATCS). This is a review on the 19th International Symposium on Distributed Computing, which took place in Kraków, Poland, on September 26--29, 2005. The proceedings of DISC 2005 are published by Springer, as volume 3724 of the Lecture Notes in Computer Science (LNCS) series. The conference website can be found at www.mimuw.edu.pl/~disc2005.An algebraic view of the relation between largest common subtrees and smallest common supertrees
http://hdl.handle.net/2117/87254
An algebraic view of the relation between largest common subtrees and smallest common supertrees
Rosselló, Francesc; Valiente Feruglio, Gabriel Alejandro
The relationship between two important problems in tree pattern matching, the largest common subtree and the smallest common supertree of two trees, is established by means of simple constructions, which allow one to obtain the largest common subtree from the smallest common supertree, and vice versa. These constructions are given for the problems of isomorphic, homeomorphic, topological, and minor embeddings. They can be implemented by a straightforward extension of any algorithm that solves one of the two problems, and the extension only takes time linear in the size of the trees.
2016-05-24T07:04:02ZRosselló, FrancescValiente Feruglio, Gabriel AlejandroThe relationship between two important problems in tree pattern matching, the largest common subtree and the smallest common supertree of two trees, is established by means of simple constructions, which allow one to obtain the largest common subtree from the smallest common supertree, and vice versa. These constructions are given for the problems of isomorphic, homeomorphic, topological, and minor embeddings. They can be implemented by a straightforward extension of any algorithm that solves one of the two problems, and the extension only takes time linear in the size of the trees.Minimal representations for majority games
http://hdl.handle.net/2117/86215
Minimal representations for majority games
Freixas Bosch, Josep; Molinero Albareda, Xavier; Roura Ferret, Salvador
This paper presents some new results about majority games. Isbell (1959) was the first to find a majority game without a minimum normalized representation; he needed 12 voters to construct such a game. Since then, it has been an open problem to find the minimum number of voters of a majority game without a minimum normalized representation. Our main new results are: 1. All majority games with less than 9 voters have a minimum representation. 2. For 9 voters there are 14 majority games without a minimum integer representation, but these games admit a minimal normalized integer representation. 3. For 10 voters exist majority games with neither a minimum integer representation nor a minimal normalized integer representation.
2016-04-27T07:22:54ZFreixas Bosch, JosepMolinero Albareda, XavierRoura Ferret, SalvadorThis paper presents some new results about majority games. Isbell (1959) was the first to find a majority game without a minimum normalized representation; he needed 12 voters to construct such a game. Since then, it has been an open problem to find the minimum number of voters of a majority game without a minimum normalized representation. Our main new results are: 1. All majority games with less than 9 voters have a minimum representation. 2. For 9 voters there are 14 majority games without a minimum integer representation, but these games admit a minimal normalized integer representation. 3. For 10 voters exist majority games with neither a minimum integer representation nor a minimal normalized integer representation.Stars and celebrities: A network creation game
http://hdl.handle.net/2117/83229
Stars and celebrities: A network creation game
Álvarez Faura, M. del Carme; Blesa Aguilera, Maria Josep; Duch Brown, Amalia; Messegué Buisan, Arnau; Serna Iglesias, María José
Celebrity games, a new model of network creation games is introduced. The specific features of this model are that players have different celebrity weights and that a critical distance is taken into consideration. The aim of any player is to be close (at distance less than critical) to the others, mainly to those with high celebrity weights. The cost of each player depends on the cost of establishing direct links to other players and on the sum of the weights of those players at a distance greater than the critical distance. We show that celebrity games always have pure Nash equilibria and we characterize the family of subgames having connected Nash equilibria, the so called star celebrity games. Exact bounds for the PoA of non star celebrity games and a bound of O(n/ß+ß) for star celebrity games are provided.
The upper bound on the PoA can be tightened when restricted to particular classes of Nash equilibria graphs. We show that the upper bound is O(n/ß) in the case of 2-edge-connected graphs and 2 in the case of trees.
CoRR
2016-02-22T09:39:41ZÁlvarez Faura, M. del CarmeBlesa Aguilera, Maria JosepDuch Brown, AmaliaMessegué Buisan, ArnauSerna Iglesias, María JoséCelebrity games, a new model of network creation games is introduced. The specific features of this model are that players have different celebrity weights and that a critical distance is taken into consideration. The aim of any player is to be close (at distance less than critical) to the others, mainly to those with high celebrity weights. The cost of each player depends on the cost of establishing direct links to other players and on the sum of the weights of those players at a distance greater than the critical distance. We show that celebrity games always have pure Nash equilibria and we characterize the family of subgames having connected Nash equilibria, the so called star celebrity games. Exact bounds for the PoA of non star celebrity games and a bound of O(n/ß+ß) for star celebrity games are provided.
The upper bound on the PoA can be tightened when restricted to particular classes of Nash equilibria graphs. We show that the upper bound is O(n/ß) in the case of 2-edge-connected graphs and 2 in the case of trees.Modelling service-oriented computing with temporal symbolic graph transformation systems
http://hdl.handle.net/2117/81101
Modelling service-oriented computing with temporal symbolic graph transformation systems
Mylonakis Pascual, Nicolás; Orejas Valdés, Fernando; Fiadeiro, José
In this paper, we present a novel semantics for an essential aspect of service-oriented computing: the mechanism through which systems evolve through a symbiosis of state transformations and run-time service discovery and binding.
The semantics is based on a new notion of temporal symbolic graph-transformation systems:
in temporal symbolic graphs, interfaces can be specified using temporal logic, and service-level agreements can be specified in that logic's propositional fragment.
An important advantage of our framework is that it can be supported by tools that implement temporal symbolic graph transformations, which would also provide a means of animating service-oriented systems evolution.
We illustrate our semantics with a simple trip-booking service.
2016-01-07T12:16:21ZMylonakis Pascual, NicolásOrejas Valdés, FernandoFiadeiro, JoséIn this paper, we present a novel semantics for an essential aspect of service-oriented computing: the mechanism through which systems evolve through a symbiosis of state transformations and run-time service discovery and binding.
The semantics is based on a new notion of temporal symbolic graph-transformation systems:
in temporal symbolic graphs, interfaces can be specified using temporal logic, and service-level agreements can be specified in that logic's propositional fragment.
An important advantage of our framework is that it can be supported by tools that implement temporal symbolic graph transformations, which would also provide a means of animating service-oriented systems evolution.
We illustrate our semantics with a simple trip-booking service.Adaptive clock with useful jitter
http://hdl.handle.net/2117/27967
Adaptive clock with useful jitter
Cortadella Fortuny, Jordi; Lavagno, Luciano; López Muñoz, Pedro; Lupon Navazo, Marc; Moreno Vega, Alberto; Roca Pérez, Antoni; Sapatnekar, Sachin S.
The growing variability in nanoelectronic devices due to uncertainties from the manufacturing process and environmental conditions (power supply, temperature, aging) requires increasing design guardbands, forcing circuits to work with conservative clock frequencies. Various schemes for clock generation based on ring oscillators have been proposed with the goal to mitigate the power and performance losses
attributable to variability. However, there has been no systematic analysis to quantify the benefits of such schemes.This paper presents and analyzes an Adaptive Clocking scheme with
Useful Jitter (ACUJ) that uses variability as an opportunity to reduce power by adapting the clock frequency to the varying environmental conditions and, thus, reducing guardband margins significantly. Power can be reduced between 20% and 40% at iso-performance and performance can be boosted by similar amounts at iso-power. Additionally, energy savings can be translated to substantial advantages in terms of reliability and thermal management. More importantly, the technology can be adopted with minimal modifications to conventional EDA flows.
Report - Departament Ciències de la Computació
2015-05-19T13:40:18ZCortadella Fortuny, JordiLavagno, LucianoLópez Muñoz, PedroLupon Navazo, MarcMoreno Vega, AlbertoRoca Pérez, AntoniSapatnekar, Sachin S.The growing variability in nanoelectronic devices due to uncertainties from the manufacturing process and environmental conditions (power supply, temperature, aging) requires increasing design guardbands, forcing circuits to work with conservative clock frequencies. Various schemes for clock generation based on ring oscillators have been proposed with the goal to mitigate the power and performance losses
attributable to variability. However, there has been no systematic analysis to quantify the benefits of such schemes.This paper presents and analyzes an Adaptive Clocking scheme with
Useful Jitter (ACUJ) that uses variability as an opportunity to reduce power by adapting the clock frequency to the varying environmental conditions and, thus, reducing guardband margins significantly. Power can be reduced between 20% and 40% at iso-performance and performance can be boosted by similar amounts at iso-power. Additionally, energy savings can be translated to substantial advantages in terms of reliability and thermal management. More importantly, the technology can be adopted with minimal modifications to conventional EDA flows.On the complexity of exchanging
http://hdl.handle.net/2117/27400
On the complexity of exchanging
Molinero Albareda, Xavier; Olsen, Martin; Serna Iglesias, María José
We analyze the computational complexity of the problem of deciding
whether, for a given simple game, there exists the possibility of rearranging the participants in a set of j given losing coalitions into a set of j winning coalitions. We also look at the problem of turning winning coalitions into losing coalitions. We analyze the problem when the simple game is represented by a list of wining, losing, minimal winning or maximal loosing coalitions.
2015-04-16T17:13:57ZMolinero Albareda, XavierOlsen, MartinSerna Iglesias, María JoséWe analyze the computational complexity of the problem of deciding
whether, for a given simple game, there exists the possibility of rearranging the participants in a set of j given losing coalitions into a set of j winning coalitions. We also look at the problem of turning winning coalitions into losing coalitions. We analyze the problem when the simple game is represented by a list of wining, losing, minimal winning or maximal loosing coalitions.Event-based real-time decomposed conformance analysis
http://hdl.handle.net/2117/22872
Event-based real-time decomposed conformance analysis
vanden Broucke, Seppe; Muñoz Gama, Jorge; Carmona Vargas, Josep; Baesens, Bart; Vanthienen, Jan
Process mining deals with the extraction of knowledge from event logs. One important task within this research field is denoted as conformance checking, which aims to diagnose deviations and discrepancies between modeled behavior and real-life, observed behavior. Conformance checking techniques still face some challenges, among which scalability, timeliness and traceability issues. In this paper, we propose a novel conformance analysis methodology to support the real-time monitoring of event-based data streams, which is shown to be more efficient than related approaches and able to localize deviations in a more fine-grained manner. Our developed approach can be directly applied in business process contexts where rapid reaction times are crucial; an exhaustive case example is provided to evidence the validity of the approach.
2014-05-07T07:49:48Zvanden Broucke, SeppeMuñoz Gama, JorgeCarmona Vargas, JosepBaesens, BartVanthienen, JanProcess mining deals with the extraction of knowledge from event logs. One important task within this research field is denoted as conformance checking, which aims to diagnose deviations and discrepancies between modeled behavior and real-life, observed behavior. Conformance checking techniques still face some challenges, among which scalability, timeliness and traceability issues. In this paper, we propose a novel conformance analysis methodology to support the real-time monitoring of event-based data streams, which is shown to be more efficient than related approaches and able to localize deviations in a more fine-grained manner. Our developed approach can be directly applied in business process contexts where rapid reaction times are crucial; an exhaustive case example is provided to evidence the validity of the approach.On the proper intervalization of colored caterpillar trees
http://hdl.handle.net/2117/12953
On the proper intervalization of colored caterpillar trees
Álvarez Faura, M. del Carme; Serna Iglesias, María José
This paper studies the computational complexity of the Proper interval colored graph problem (picg), when the input graph is a colored caterpillar, parameterized by hair length. In order prove our result we establish a close relationship between the picg and a graph layout problem the Proper colored layout problem (pclp). We show a dichotomy: the picg and the pclp are NP-complete for colored caterpillars of hair length ≥ 2, while both problems are in P for colored caterpillars of hair length < 2. For the hardness results we provide a reduction from the Multiprocessor Scheduling problem, while the polynomial time results follow from a characterization in terms of forbidden subgraphs.
2011-07-13T09:48:20ZÁlvarez Faura, M. del CarmeSerna Iglesias, María JoséThis paper studies the computational complexity of the Proper interval colored graph problem (picg), when the input graph is a colored caterpillar, parameterized by hair length. In order prove our result we establish a close relationship between the picg and a graph layout problem the Proper colored layout problem (pclp). We show a dichotomy: the picg and the pclp are NP-complete for colored caterpillars of hair length ≥ 2, while both problems are in P for colored caterpillars of hair length < 2. For the hardness results we provide a reduction from the Multiprocessor Scheduling problem, while the polynomial time results follow from a characterization in terms of forbidden subgraphs.Sensor field: a computational model
http://hdl.handle.net/2117/12934
Sensor field: a computational model
Álvarez Faura, M. del Carme; Duch Brown, Amalia; Gabarró Vallès, Joaquim; Serna Iglesias, María José
We introduce a formal model of computation for networks of tiny artifacts, the static synchronous sensor field model (SSSF) which
considers that the devices communicate through a fixed communication graph and interact with the environment through input/output data streams. We analyze the performance of SSSFs solving two sensing problems the Average Monitoring and the Alerting problems. For constant memory SSSFs we show that the set of recognized languages is contained in DSPACE(n+m) where n is the number of nodes of the communication graph and m its number of edges. Finally we explore the capabilities of SSSFs having sensing and additional non-sensing constant memory devices.
2011-07-12T10:23:04ZÁlvarez Faura, M. del CarmeDuch Brown, AmaliaGabarró Vallès, JoaquimSerna Iglesias, María JoséWe introduce a formal model of computation for networks of tiny artifacts, the static synchronous sensor field model (SSSF) which
considers that the devices communicate through a fixed communication graph and interact with the environment through input/output data streams. We analyze the performance of SSSFs solving two sensing problems the Average Monitoring and the Alerting problems. For constant memory SSSFs we show that the set of recognized languages is contained in DSPACE(n+m) where n is the number of nodes of the communication graph and m its number of edges. Finally we explore the capabilities of SSSFs having sensing and additional non-sensing constant memory devices.