Now showing items 21-40 of 136

    • Analysis of methods for generating octree models of objects from their silhouettes 

      Franquesa Niubó, Marta; Brunet Crosa, Pere (1997-01)
      Article
      Restricted access - publisher's policy
      Reconstructing 3D models from their projection images has been an interesting research topic in computer vision and geometric modeling. In this paper, we review several methods that generate octree models of objects from ...
    • Approximate formulae for a logic that capture classes of computational complexity 

      Arratia Quesada, Argimiro Alejandro; Ortiz, Carlos E. (Oxford University Press, 2009-02)
      Article
      Open Access
      This paper presents a syntax of approximate formulae suited for the logic with counting quantifiers SOLP. This logic was formalised by us in [1] where, among other properties, we showed the following facts: (i) In the ...
    • Augmenting the power of (partial) MaxSat resolution with extension 

      Larrosa Bondia, Francisco Javier; Rollón Rico, Emma (AAAI Press, 2020)
      Conference lecture
      Restricted access - publisher's policy
      The refutation power of SAT and MaxSAT resolution is challenged by problems like the soft and hard Pigeon Hole Problem PHP for which short refutations do not exist. In this paper we augment the MaxSAT resolution proof ...
    • Automating resolution is NP-Hard 

      Atserias, Albert; Muller, Moritz Martin (2020-09)
      Article
      Open Access
      We show that the problem of finding a Resolution refutation that is at most polynomially longer than a shortest one is NP-hard. In the parlance of proof complexity, Resolution is not automatable unless P = NP. Indeed, we ...
    • Automating Resolution is NP-hard 

      Atserias, Albert; Muller, Moritz Martin (Institute of Electrical and Electronics Engineers (IEEE), 2019)
      Conference report
      Open Access
      We show that the problem of finding a Resolution refutation that is at most polynomially longer than a shortest one is NP-hard. In the parlance of proof complexity, Resolution is not automatizable unless P = NP. Indeed, ...
    • Average complexity of algorithms on trees 

      Cases Muñoz, Rafael; Steyaert, Jean-Marc (1985)
      External research report
      Open Access
      In this work we count the number of structures resulting from the application of different kinds of structure modifying algorithms on binary trees
    • Average-case analysis of equality of binary trees under the BST probability model 

      Martínez Parra, Conrado (1991-03)
      External research report
      Open Access
      In this paper a simple algorithm to test equality of binary trees currently used in symbolic computation, unification, etc. is investigated. Surprisingly enough, it takes 0(1) steps on average to decide if a given pair of ...
    • Best response computation: efficient algorithm to compute the best response for strategic network formation with attack and immunization 

      Zhang, Niebo (Universitat Politècnica de Catalunya, 2021-05-25)
      Bachelor thesis
      Open Access
      En aquest projecte, ens centrem en investigar el model de Network Creation Games with attack and immunization introduït per Goyal et al.. Freqüentment, el cost computacional de computar una Best Response o de comprovar si ...
    • Bounded queries to arbitrary sets 

      Lozano Bojados, Antoni (1991-09)
      External research report
      Open Access
      We prove that if P superA[k] = P superA[k+1] for some k and an arbitrary set A, then A is reducible to its complement under a relativized nondeterministic conjunctive reduction. This result shows the first known property ...
    • Bounded-width QBF is PSPACE-complete 

      Atserias, Albert; Oliva Valls, Sergi (Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 2013)
      Conference report
      Open Access
      Tree-width is a well-studied parameter of structures that measures their similarity to a tree. Many important NP-complete problems, such as Boolean satisfiability (SAT), are tractable on bounded tree-width instances. In ...
    • Bounded-width QBF is PSPACE-complete 

      Atserias, Albert; Oliva Valls, Sergi (2014-11-01)
      Article
      Open Access
      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, ...
    • Celebrity games 

      Álvarez Faura, M. del Carme; Blesa Aguilera, Maria Josep; Duch Brown, Amalia; Messegué Buisan, Arnau; Serna Iglesias, María José (2016-10-04)
      Article
      Open Access
      We introduce Celebrity games, a new model of network creation games. In this model players have weights (W being the sum of all the player's weights) and there is a critical distance ß as well as a link cost a. The cost ...
    • Circular (yet sound) proofs 

      Atserias, Albert; Lauria, Massimo (Springer, 2019)
      Conference report
      Open Access
      We introduce a new way of composing proofs in rule-based proof systems that generalizes tree-like and dag-like proofs. In the new definition, proofs are directed graphs of derived formulas, in which cycles are allowed as ...
    • Clique is hard on average for regular resolution 

      Atserias, Albert; Bonacina, Ilario; Rezende, Susanna F. de; Lauria, Massimo; Nordström, Jakob; Razborov, Alexander (Association for Computing Machinery (ACM), 2018)
      Conference report
      Open Access
      We prove that for k ≪4√n regular resolution requires length nΩ(k) to establish that an Erdős–Rényi graph with appropriately chosen edge density does not contain a k-clique. This lower bound is optimal up to the multiplicative ...
    • Complexity in safety-critical systems 

      Ponsa Asensio, Pere (2012-10-03)
      Article
      Open Access
    • Complexity measures for resolution 

      Esteban Ángeles, Juan Luis (Universitat Politècnica de Catalunya, 2003-12-15)
      Doctoral thesis
      Open Access
      Esta obra es una contribución al campo de la Complejidad de la Demostración, que estudia la complejidad de los sistemas de demostración en términos de los recursos necesarios para demostrar o refutar fórmulas proposicionales. ...
    • Computational complexity of small descriptions 

      Gavaldà Mestre, Ricard; Watanabe, Osamu (1990-11-19)
      External research report
      Open Access
      For a set L that is polynomial time reducible (in short, = sub T super P-reducible) to some sparse set, we investigate the computational complexity of such sparse sets relative to L. We construct sets A and B such that ...
    • Connections among non uniform models for problems requiring high amount of resources 

      Balcázar Navarro, José Luis; Gabarró Vallès, Joaquim (1985-11)
      External research report
      Open Access
      We characterize in terms of oracle Turing machines the classes defined by exponential lower bounds on some nonuniform complexity measures. After, we use the same methods to give a new characterization of classes defined ...
    • Constant-time approximate sliding window framework with error control 

      Villalba Navarro, Álvaro; Carrera Pérez, David (Institute of Electrical and Electronics Engineers (IEEE), 2019)
      Conference report
      Open Access
      Stream Processing is a crucial element for the Edge Computing paradigm, in which large amount of devices generate data at the edge of the network. This data needs to be aggregated and processed on-the-move across different ...
    • Cooperation through social influence 

      Molinero Albareda, Xavier; Riquelme Csori, Fabián; Serna Iglesias, María José (Elsevier, 2015-05-01)
      Article
      Open Access
      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. ...