Now showing items 21-40 of 69

    • Computational power of neural networks: a Kolmogorov complexity characterization 

      Balcázar Navarro, José Luis; Gavaldà Mestre, Ricard; Siegelmann, H. (1993-01-01)
      External research report
      Open Access
      The computational power of neural networks depends on properties of the real numbers used as weights. We focus on networks restricted to compute in polynomial time, operating on boolean inputs. Previous work has demonstrated ...
    • 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 ...
    • De cómo ciertos conjuntos no pueden ser NP-completos 

      Balcázar Navarro, José Luis (Universitat Politècnica de Barcelona. Centre de Càlcul, 1982-09)
      Article
      Open Access
      En este artículo se presenta una visión general a los últimos resultados acontecidos en el área de la estructura de la clase NP-completa y su relación con el problema de si: P=NP o P diferente de NP.
    • Deciding bisimilarity is P-complete 

      Balcázar Navarro, José Luis; Gabarró Vallès, Joaquim; Santha, Miklos (1990)
      External research report
      Open Access
      On finite labelled transition systems, the problems of deciding strong bisimilarity, observation equivalence, and observation congruence are P-complete under many-one NC-reducibility. As a consequence, algorithms for ...
    • Deriving specifications of embeddings in recursive program design 

      Roselló Balanyà, Celestí; Balcázar Navarro, José Luis; Peña Marí, Ricardo (1989)
      External research report
      Open Access
      The design of recursive functions is a well-studied subject. Design methods require a specification to start with, however, when an embedding design is attempted at, it is not clear how the specification of the embedding ...
    • Diameter minimization in networks for SIMD machines 

      Beivide Palacio, Ramon; Balcázar Navarro, José Luis (1985)
      External research report
      Open Access
      We propose an algebraic constructive method which allows to find a certain kind of networks having optimal diameter. These interconnection networks have been proposed for SIMD machines. We compare the results with other ...
    • El algoritmo de compleción de Knuth-Bendix 

      Balcázar Navarro, José Luis (1988)
      External research report
      Open Access
      An introduction to the confluence and finite termination properties of rewriting systems is presented and also to the Kunth-Bendix completion algorithm is presented.
    • Embedding: a unifying concept for recursive program design 

      Roselló Balanyà, Celestí; Balcázar Navarro, José Luis; Peña Marí, Ricardo (1988)
      External research report
      Open Access
      The concept of embedding one function into another is used to get a unified view of some well-known design techniques, such as loop derivation using inveriants, recursion removal, or folding-unfolding. A design method for ...
    • Empirical results on long-lived renaming algorithms 

      Moral Boadas, Sandra; Balcázar Navarro, José Luis (1997-09)
      External research report
      Open Access
      The Long-lived Renaming problem is an important subject in Distributed Algorithms. The Renaming problem consists in providing processes with new names from a hopefully smaller name space. In the long-lived version, only ...
    • Entailment among probabilistic implications 

      Atserias, Albert; Balcázar Navarro, José Luis (Institute of Electrical and Electronics Engineers (IEEE), 2015)
      Conference report
      Open Access
      We study a natural variant of the implicational fragment of propositional logic. Its formulas are pairs of conjunctions of positive literals, related together by an implicational-like connective, the semantics of this sort ...
    • Examples of CF-bi-inmune and CF-levelable sets in LOGSPACE 

      Balcázar Navarro, José Luis; Díaz Cort, Josep; Gabarró Vallès, Joaquim (1984)
      External research report
      Open Access
      We find sets in the class LOGSPACE (on-line) that do not have good respectively approximations by context-free languages. For that we introduce the languages CF-bi-inmune and CF-levelable. We prove the results by defining ...
    • Frequent sets, sequences, and taxonomies: new, efficient algorithmic proposals 

      Baixeries i Juvillà, Jaume; Casas Garriga, Gemma; Balcázar Navarro, José Luis (2000-12)
      External research report
      Open Access
      We describe efficient algorithmic proposals to approach three fundamental problems in data mining: association rules, episodes in sequences, and generalized association rules over hierarchical taxonomies. The association ...
    • Functional oracle queries as a measure of parallel time 

      Álvarez Faura, M. del Carme; Balcázar Navarro, José Luis; Jenner Núñez, Birgit (1990-08)
      External research report
      Open Access
      We discuss two notions of functional oracle for logarithmic space-bounded machines, which differ in whether there is only one oracle tape for both the query and the answer or a separate tape for the answer, which can still ...
    • Generalized Kolmogorov complexity in relativized separations 

      Gavaldà Mestre, Ricard; Torenvliet, Leen; Watanabe, Osamu; Balcázar Navarro, José Luis (1990-04)
      External research report
      Open Access
      We describe several developments of a technique, due to Hartmanis, that uses Kolmogorov complexity to prove the existence of relativizations separating complexity classes. The main advantage of these proofs is that they ...
    • Global optimality in k-means clustering 

      Tîrnauca, Cristina; Gómez Pérez, Domingo; Balcázar Navarro, José Luis; Montaña Arnaiz, José Luis (2018-05-01)
      Article
      Open Access
      We study the problem of finding an optimum clustering, a problem known to be NP-hard. Existing literature contains algorithms running in time proportional to the number of points raised to a power that depends on the ...
    • Horn axiomatizations for sequential data 

      Balcázar Navarro, José Luis; Casas Garriga, Gemma (2005-09)
      External research report
      Open Access
      We propose a notion of deterministic association rules for ordered data. We prove that our proposed rules can be formally justified by a purely logical characterization, namely, a natural notion of empirical Horn approximation ...
    • Immunity and simplicity in relativizations of probabilistic complexity classes 

      Balcázar Navarro, José Luis; Russo, David A. (1988-05)
      Article
      Open Access
      The existence of immune and simple sets in relativizations of the probabilistic polynomial time bounded classes is studied. Some techniques previously used to show similar results for relativizations of P and NP are adapted ...
    • Iterator-based algorithms in self-tuning discovery of partial implications 

      Balcázar Navarro, José Luis; García Sáiz, Diego; de la Dehesa, Javier (CEUR Workshop Proceedings, 2012)
      Conference report
      Open Access
      We describe the internal algorithmics of our recent implementation of a closure-based self-tuning associator: yacaree. This system is designed so as not to request the user to specify any threshold. In order to avoid the ...
    • Learnability of Kolmogorov-easy circuit expressions via queries 

      Balcázar Navarro, José Luis; Buhrman, H; Hermo, M (1995-02)
      External research report
      Open Access
      Circuit expressions were introduced to provide a natural link between Computational Learning and certain aspects of Structural Complexity. Upper and lower bounds on the learnability of circuit expressions are known. We ...
    • Learning definite Horn formulas from closure queries 

      Arias Vicente, Marta; Balcázar Navarro, José Luis; Tîrnauca, Cristina (2017-01-07)
      Article
      Open Access
      A definite Horn theory is a set of n-dimensional Boolean vectors whose characteristic function is expressible as a definite Horn formula, that is, as conjunction of definite Horn clauses. The class of definite Horn theories ...