DSpace Collection:
http://hdl.handle.net/2117/3093
2015-07-07T09:26:26ZThe ordering principle in a fragment of approximate counting
http://hdl.handle.net/2117/28288
Title: The ordering principle in a fragment of approximate counting
Authors: Atserias Peri, Albert; Thapen, Neil
Abstract: The ordering principle states that every finite linear order has a least element. We show that, in the relativized setting, the surjective weak pigeonhole principle for polynomial time functions does not prove a Herbrandized version of the ordering principle over T-2(1). This answers an open question raised in Buss et al. [2012] and completes their program to compare the strength of Jerabek's bounded arithmetic theory for approximate counting with weakened versions of it.2015-06-12T08:41:44ZProcess discovery algorithms using numerical abstract domains
http://hdl.handle.net/2117/28272
Title: Process discovery algorithms using numerical abstract domains
Authors: Carmona Vargas, Josep; Cortadella Fortuny, Jordi
Abstract: The discovery of process models from event logs has emerged as one of the crucial problems for enabling the continuous support in the life-cycle of an information system. However, in a decade of process discovery research, the algorithms and tools that have appeared are known to have strong limitations in several dimensions. The size of the logs and the formal properties of the model discovered are the two main challenges nowadays. In this paper we propose the use of numerical abstract domains for tackling these two problems, for the particular case of the discovery of Petri nets. First, numerical abstract domains enable the discovery of general process models, requiring no knowledge (e.g., the bound of the Petri net to derive) for the discovery algorithm. Second, by using divide and conquer techniques we are able to control the size of the process discovery problems. The methods proposed in this paper have been implemented in a prototype tool and experiments are reported illustrating the significance of this fresh view of the process discovery problem.2015-06-11T09:06:20ZFirefighting as a game
http://hdl.handle.net/2117/28172
Title: Firefighting as a game
Authors: Álvarez Faura, M. del Carme; Blesa Aguilera, Maria Josep; Molter, Hendrik
Abstract: The Firefighter Problem was proposed in 1995 [16] as a deterministic discrete-time model for the spread (and containment) of a fire. Its applications reach from real fires to the spreading of diseases and the containment of floods. Furthermore, it can be used to model the spread of computer viruses or viral marketing in communication networks.
In this work, we study the problem from a game-theoretical perspective. Such a context seems very appropriate when applied to large networks, where entities may act and make decisions based on their own interests, without global coordination.
We model the Firefighter Problem as a strategic game where there is one player for each time step who decides where to place the firefighters. We show that the Price of Anarchy is linear in the general case, but at most 2 for trees. We prove that the quality of the equilibria improves when allowing coalitional cooperation among players. In general, we have that the Price of Anarchy is in T(n/k) where k is the coalition size. Furthermore, we show that there are topologies which have a constant Price of Anarchy even when constant sized coalitions are considered.2015-06-04T08:27:45ZLower bounds for DNF-refutations of a relativized weak pigeonhole principle
http://hdl.handle.net/2117/28085
Title: Lower bounds for DNF-refutations of a relativized weak pigeonhole principle
Authors: Atserias Peri, Albert; Müller, Moritz; Oliva Valls, Sergi
Abstract: The relativized weak pigeonhole principle states that if at least 2n out of n(2) pigeons fly into n holes, then some hole must be doubly occupied. We prove that every DNF-refutation of the CNF encoding of this principle requires size 2((log n)3/2-is an element of) for every is an element of > 0 and every sufficiently large n. By reducing it to the standard weak pigeonhole principle with 2n pigeons and n holes, we also show that this lower bound is essentially tight in that there exist DNF-refutations of size 2((log n)O(1)) even in R(log). For the lower bound proof we need to discuss the existence of unbalanced low-degree bipartite expanders satisfying a certain robustness condition.2015-05-28T07:25:26ZBounded-width QBF is PSPACE-complete
http://hdl.handle.net/2117/27300
Title: Bounded-width QBF is PSPACE-complete
Authors: Atserias Peri, Albert; Oliva Valls, Sergi
Abstract: Tree-width and path-width are two well-studied parameters of structures that measure their similarity to a tree and a path, respectively. We show that QBF on instances with constant path-width, and hence constant tree-width, remains PSPACE-complete. This answers a question by Vardi. We also show that on instances with constant path-width and a very slow-growing number of quantifier alternations (roughly inverse-Ackermann many in the number of variables), the problem remains NP-hard. Additionally, we introduce a family of formulas with bounded tree-width that do have short refutations in Q-resolution, the natural generalization of resolution for quantified Boolean formulas.2015-04-14T08:29:15ZA boolean rule-based approach for manufacturability-aware cell routing
http://hdl.handle.net/2117/27267
Title: A boolean rule-based approach for manufacturability-aware cell routing
Authors: Cortadella Fortuny, Jordi; Petit Silvestre, Jordi; Gómez Fernández, Sergio; Moll Echeto, Francisco de Borja
Abstract: An approach for cell routing using gridded design rules is proposed. It is technology-independent and parameterizable for different fabrics and design rules, including support for multiple-patterning lithography. The core contribution is a detailed-routing algorithm based on a Boolean formulation of the problem. The algorithm uses a novel encoding scheme, graph theory to support floating terminals, efficient heuristics to reduce the computational cost, and minimization of the number of unconnected pins in case the cell is unroutable. The versatility of the algorithm is demonstrated by routing single-and double-height cells. The efficiency is ascertained by synthesizing a library with 127 cells in about one hour and a half of CPU time. The layouts derived by the implemented tool have also been compared with the ones from a commercial library; thus, showing the competitiveness of the approach for gridded geometries.2015-04-13T09:46:45ZArea-optimal transistor folding for 1-D gridded cell design
http://hdl.handle.net/2117/27265
Title: Area-optimal transistor folding for 1-D gridded cell design
Authors: Cortadella Fortuny, Jordi
Abstract: The 1-D design style with gridded design rules is gaining ground for addressing the printability issues in subwavelength photolithography. One of the synthesis problems in cell generation is transistor folding, which consists of breaking large transistors into smaller ones (legs) that can be placed in the active area of the cell. In the 1-D style, diffusion sharing between differently sized transistors is not allowed, thus implying a significant area overhead when active areas with different sizes are required. This paper presents a new formulation of the transistor folding problem in the context of 1-D design style and a mathematical model that delivers area-optimal solutions. The mathematical model can be customized for different variants of the problem, considering flexible transistor sizes and multiple-height cells. An innovative feature of the method is that area optimality can be guaranteed without calculating the actual location of the transistors. The model can also be enhanced to deliver solutions with good routability properties.2015-04-13T09:20:30ZPartially definable forcing and bounded arithmetic
http://hdl.handle.net/2117/27193
Title: Partially definable forcing and bounded arithmetic
Authors: Atserias Peri, Albert; Müller, Moritz
Abstract: We describe a method of forcing against weak theories of arithmetic and its applications in propositional proof complexity.2015-04-09T07:48:00ZTrustworthiness in P2P: performance behaviour of two fuzzy-based systems for JXTA-overlay platform
http://hdl.handle.net/2117/27102
Title: Trustworthiness in P2P: performance behaviour of two fuzzy-based systems for JXTA-overlay platform
Authors: Spaho, Evjola; Sakamoto, Shinji; Barolli, Leonard; Xhafa Xhafa, Fatos; Ikeda, Makoto
Abstract: Peer-to-peer (P2P) networks, will be very important for future distributed systems and applications. In such networks, peers are heterogeneous in providing the services and they do not have the same competence of reliability. Therefore, it is necessary to estimate whether a peer is trustworthy or not for file sharing and other services. In this paper, we propose two fuzzy-based trustworthiness system for P2P communication in JXTA-overlay. System 1 has only one fuzzy logic controller (FLC) and uses four input parameters: mutually agreed behaviour (MAB), actual behaviour criterion (ABC), peer disconnections (PD) and number of uploads (NU) and the output is peer reliability (PR). System 2 has two FLCs. In FLC1 use three input parameters: number of jobs (NJ), number of connections (NC) and connection lifetime (CL) and the output is actual behavioural criterion (ABC). We use ABC and reputation (R) as input linguistic parameters for FLC2 and the output is peer reliability (PR). We evaluate the proposed systems by computer simulations. The simulation results show that the proposed systems have a good behaviour and can be used successfully to evaluate the reliability of the new peer connected in JXTA-overlay.2015-03-27T15:44:52ZMeasuring precision of modeled behavior
http://hdl.handle.net/2117/26715
Title: Measuring precision of modeled behavior
Authors: Adriansyah, Arya; Muñoz Gama, Jorge; Carmona Vargas, Josep; Van Dongen, Boudewijn; van der Aalst, Wil M. P.
Abstract: Conformance checking techniques compare observed behavior (i.e., event logs) with modeled behavior for a variety of reasons. For example, discrepancies between a normative process model and recorded behavior may point to fraud or inefficiencies. The resulting diagnostics can be used for auditing and compliance management. Conformance checking can also be used to judge a process model automatically discovered from an event log. Models discovered using different process discovery techniques need to be compared objectively. These examples illustrate just a few of the many use cases for aligning observed and modeled behavior. Thus far, most conformance checking techniques focused on replay fitness, i.e., the ability to reproduce the event log. However, it is easy to construct models that allow for lots of behavior (including the observed behavior) without being precise. In this paper, we propose a method to measure precision of process models, given their event logs by first aligning the logs to the models. This way, the measurement is not sensitive to non-fitting executions and more accurate values can be obtained for non-fitting logs. Furthermore, we introduce several variants of the technique to deal better with incomplete logs and reduce possible bias due to behavioral property of process models. The approach has been implemented in the ProM 6 framework and tested against both artificial and real-life cases. Experiments show that the approach is robust to noise and applicable to handle logs and models of real-life complexity.2015-03-16T11:04:52ZDegree lower bounds of tower-type for approximating formulas with parity quantifiers
http://hdl.handle.net/2117/26697
Title: Degree lower bounds of tower-type for approximating formulas with parity quantifiers
Authors: Atserias Peri, Albert; Dawar, Anuj
Abstract: Kolaitis and Kopparty have shown that for any first-order formula with parity quantifiers over the language of graphs, there is a family of multivariate polynomials of constant-degree that agree with the formula on all but a 2(-Omega(n))-fraction of the graphs with n vertices. The proof bounds the degree of the polynomials by a tower of exponentials whose height is the nesting depth of parity quantifiers in the formula. We show that this tower-type dependence is necessary. We build a family of formulas of depth q whose approximating polynomials must have degree bounded from below by a tower of exponentials of height proportional to q. Our proof has two main parts. First, we adapt and extend the results by Kolaitis and Kopparty that describe the joint distribution of the parities of the numbers of copies of small subgraphs in a random graph to the setting of graphs of growing size. Second, we analyze a variant of Karp's graph canonical labeling algorithm and exploit its massive parallelism to get a formula of low depth that defines an almost canonical pre-order on a random graph.2015-03-13T13:18:21ZCooperation through social influence
http://hdl.handle.net/2117/26600
Title: Cooperation through social influence
Authors: Molinero Albareda, Xavier; Riquelme Csori, Fabián; Serna Iglesias, María José
Abstract: We consider a simple and altruistic multiagent system in which the agents are eager to perform a collective task but where their real engagement depends on the willingness to perform the task of other influential agents. We model this scenario by an influence game, a cooperative simple game in which a team (or coalition) of players succeeds if it is able to convince enough agents to participate in the task (to vote in favor of a decision). We take the linear threshold model as the influence model. We show first the expressiveness of influence games showing that they capture the class of simple games. Then we characterize the computational complexity of various problems on influence games, including measures (length and width), values (Shapley-Shubik and Banzhaf) and properties (of teams and players). Finally, we analyze those problems for some particular extremal cases, with respect to the propagation of influence, showing tighter complexity characterizations.2015-03-05T17:47:09ZOn the complexity of problems on simple games
http://hdl.handle.net/2117/25093
Title: On the complexity of problems on simple games
Authors: Freixas Bosch, Josep; Molinero Albareda, Xavier; Olsen, Martin; Serna Iglesias, María José
Abstract: Simple games cover voting systems in which a single alter-
native, such as a bill or an amendment, is pitted against the status quo. A simple game or a yes-no voting system is a set of rules that specifies exactly which collections of “yea” votes yield passage of the issue at hand. Each of these collections of “yea” voters forms a winning coalition. We are interested in performing a complexity analysis on problems defined on such families of games. This analysis as usual depends on the game representation used as input. We consider four natural explicit representations: winning, losing, minimal winning, and maximal losing. We first analyze the complexity of testing whether a game is simple and testing whether a game is weighted. We show that, for the four types of representations, both problems can be solved in polynomial time. Finally, we provide results on the complexity of testing whether a simple game or a weighted game is of a special type. We analyze strongness, properness, weightedness, homogeneousness, decisiveness and majorityness, which are desirable properties to be fulfilled for a simple game.
Finally, we consider the possibility of representing a game in a more
succinct and natural way and show that the corresponding recognition
problem is hard.2014-12-18T19:12:37ZLong non-coding RNAs as a source of new peptides
http://hdl.handle.net/2117/24421
Title: Long non-coding RNAs as a source of new peptides
Authors: Ruiz Orera, Jorge; Messeguer Peypoch, Xavier; Subirana Torrent, Juan A.; Albà Soler, M. Mar
Abstract: Deep transcriptome sequencing has revealed the existence of many transcripts that lack long or conserved open reading frames (ORFs) and which have been termed long non-coding RNAs (lncRNAs). The vast majority of lncRNAs are lineage-specific and do not yet have a known function. In this study, we test the hypothesis that they may act as a repository for the synthesis of new peptides. We find that a large fraction of the lncRNAs expressed in cells from six different species is associated with ribosomes. The patterns of ribosome protection are consistent with the translation of short peptides. lncRNAs show similar coding potential and sequence constraints than evolutionary young protein coding sequences, indicating that they play an important role in de novo protein evolution.2014-10-20T08:38:40ZPower indices of influence games and new centrality measures for agent societies and social networks
http://hdl.handle.net/2117/24245
Title: Power indices of influence games and new centrality measures for agent societies and social networks
Authors: Molinero Albareda, Xavier; Riquelme Csori, Fabián; Serna Iglesias, María José
Abstract: We propose as centrality measures for social networks two classical power indices, Banzhaf and Shapley-Shubik, and two new measures, effort and satisfaction, related to the spread of influence process that emerge from the subjacent influence game. We perform a comparison of these measures with three well known centrality measures, degree, closeness and betweenness, applied to three simple social networks.2014-10-03T13:58:17Z