Ara es mostren els items 1-20 de 59

  • Absorption time of the Moran process 

    Díaz Cort, Josep; Goldberg, Leslie Ann; Richerby, David; Serna Iglesias, María José (2016-08-01)
    Article
    Accés obert
    © 2016 Wiley Periodicals, Inc. The Moran process models the spread of mutations in populations on graphs. We investigate the absorption time of the process, which is the time taken for a mutation introduced at a randomly ...
  • Adversarial models for priority-based networks 

    Álvarez Faura, M. del Carme; Díaz Cort, Josep; Blesa Aguilera, Maria Josep; Fernández Anta, Antonio; Serna Iglesias, María José (2003-06)
    Report de recerca
    Accés obert
    We propose several variations of the adversarial queueing model. The priority model takes into account the case in which the packets can have different priorities, assigned by the adversary at injection time. The ...
  • Algorithms for learning finite automata from queries: a unified view 

    Balcázar Navarro, José Luis; Díaz Cort, Josep; Gavaldà Mestre, Ricard; Watanabe, Osamu (1996-09)
    Report de recerca
    Accés obert
    In this survey we compare several known variants of the algorithm for learning deterministic finite automata via membership and equivalence queries. We believe that our presentation makes it easier to understand what ...
  • Algunes consideracions teòriques al problema de la construcció d’horaris (comunicació breu) 

    Berenguer, Xavier; Díaz Cort, Josep (Universitat Politècnica de Barcelona. Centre de Càlcul, 1980-03)
    Article
    Accés obert
    Corominas i Roselló varen presentar una visió general dels algorismes per a resoldre el problema de la construcció d'horaris en centres escolars. En aquesta comunicació es pretén completar aquest treball amb una revisió ...
  • A new upper bound for 3-SAT 

    Díaz Cort, Josep; Lefteris, Kirousis; Mitsche, Dieter; Perez-Gimenez, Xavier (Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik, Germany, 2008)
    Text en actes de congrés
    Accés obert
    We show that a randomly chosen 3-CNF formula over n variables with clauses-tovariables ratio at least 4.4898 is asymptotically almost surely unsatisfiable. The previous best such bound, due to Dubois in 1999, was 4.506. ...
  • A note on the subgraphs of the (2×\infty)-grid 

    Díaz Cort, Josep; Kaminski, Marcin; Thilikos Touloupas, Dimitrios (2010-02)
    Article
    Accés restringit per política de l'editorial
    We give a linear-time algorithm checking whether a graph is a subgraph of the (2×k)-grid for some value of k. Our algorithm is based on a detailed characterization of the structure of such graphs.
  • Approximating layout problems on random sparse graphs 

    Díaz Cort, Josep; Petit Silvestre, Jordi; Serna Iglesias, María José; Trevisan, Marco (1998-07)
    Report de recerca
    Accés obert
    We show that, with high probability, several layout problems are approximable within a constant for random graphs drawn from the standard Gnp model with p=c/n for some constant c. Our results establish that, in fact, ...
  • Approximating the permanent is in RNC 

    Díaz Cort, Josep; Serna Iglesias, María José; Spirakis, Paul George (1995-04)
    Report de recerca
    Accés obert
    In this work we look into the parallelization (in the NC sense) of the Markov Chain approach to almost random generation, as described by Sinclair (1993). We give a RNC almost uniform generator for perfect matchings in ...
  • A Random graph model for optical networks of sensors 

    Díaz Cort, Josep; Petit Silvestre, Jordi; Serna Iglesias, María José (2002-12)
    Report de recerca
    Accés obert
    In this paper we propose a model for Smart Dust Networks and show its applicability when the goal of the network is monitoring an area under the surveillance of a base station. We analyze basic parameters of these nets and ...
  • A Survey on graph layout problems 

    Díaz Cort, Josep; Petit Silvestre, Jordi; Serna Iglesias, María José (2000-10)
    Report de recerca
    Accés obert
    In this paper we survey results on several graph layout problems from an algorithmic point of view. Graph layout problems are a particular class of combinatorial optimization problems whose goal is to find a linear layout ...
  • Bisection of random cubic graphs 

    Díaz Cort, Josep; Do, Norman; Serna Iglesias, María José; Wormald, Nick (2002-05)
    Report de recerca
    Accés obert
    In this paper we present two randomized algorithms to compute the bisection width of random cubic graphs with n vertices, giving an asymptotic upper bound for the bisection width respectively of 0.174039n and 0.174501n. ...
  • Bounds on the bisection width for random d-regular graphs 

    Díaz Cort, Josep; Serna Iglesias, María José; Wormald, Nick (2004-04)
    Report de recerca
    Accés obert
    In this paper we provide an explicit way to compute asymptotically almost sure upper bounds on the bisection width of random d-regular graphs, for any value of d. The upper bounds are obtained from the analysis of the ...
  • Bounds on the max and min bisection of random cubic and 4-regular graphs 

    Díaz Cort, Josep; Do, Norman; Serna Iglesias, María José; Wormald, Nick (2002-12)
    Report de recerca
    Accés obert
    In this paper we present simple randomized algorithms to bisect cubic and 4-regular graphs. These algorithms produce bisections of size asymptotically at most 0.17404n for typical random cubic n-vertex graphs, and ...
  • Chromatic number in random scaled sector graphs 

    Díaz Cort, Josep; Sanwalani, Vishal; Serna Iglesias, María José; Spirakis, Paul George (2004-04)
    Report de recerca
    Accés obert
    In this paper, we introduce a new model of random graph that we call random sector graph. This model aims to provide a tool for studying communication problems in networks of sensors using laser communication such as ...
  • Communication tree problems 

    Álvarez Faura, M. del Carme; Cases Muñoz, Rafel; Díaz Cort, Josep; Petit Silvestre, Jordi; Serna Iglesias, María José (2001-03)
    Report de recerca
    Accés obert
    In this paper, we consider random communication requirements and several cost measures for a particular model of tree routing on a complete network. First we show that a random tree does not give any approximation. Then ...
  • Complejidad de problemas combinatorios 

    Díaz Cort, Josep (Universitat Politècnica de Barcelona. Centre de Càlcul, 1978-03)
    Article
    Accés obert
    Un gran número de problemas entre los que se encuentran problemas tan conocidos como el del viajante de comercio, o el problema isoperimétrico, se muéstran como equivalentes en el sentido de que si uno de ellos admite una ...
  • Complexity issues on bounded restrictive H-coloring 

    Serna Iglesias, María José; Díaz Cort, Josep; Thilikos Touloupas, Dimitrios (2004-04)
    Report de recerca
    Accés obert
    We consider the restriction of the H-coloring problem where we are looking for homomorphisms were the number of preimages of certain vertices of H is bounded by some fixed constant. We consider the decision and the ...
  • Complexity of metric dimension on planar graphs 

    Díaz Cort, Josep; Pottonen, Ollie; Serna Iglesias, María José; van Leeuwen, Erik Jan (2017-04-03)
    Article
    Accés obert
    The metric dimension of a graph G is the size of a smallest subset L ¿ V (G) such that for any x, y ¿ V (G) with x =/ y there is a z ¿ L such that the graph distance between x and z differs from the graph distance between ...
  • Computation of bisection width for random d-regular graphs 

    Díaz Cort, Josep; Serna Iglesias, María José; Wormald, Nick (2003-07)
    Report de recerca
    Accés obert
    In this paper we describe a randomized greedy algorithm for obtaining bisections of graphs. Analysis of the algorithm's performance on random d-regular graphs yields asymptotically almost sure upper bounds on the bisection ...
  • Continuous monitoring in the dynamic sensor field model 

    Álvarez Faura, M. del Carme; Díaz Cort, Josep; Dieter Wilhelm, Mitsche; Serna Iglesias, María José (2011-05)
    Report de recerca
    Accés obert
    In this work we consider the problem of continuously monitoring a collection of data sets produced by sensors placed on moving or static targets. We propose a modification of the static sensor field model (SSSF) [2] to ...