Now showing items 1-12 of 54

    • Adaptive logspace reducibility and parallel time 

      Álvarez Faura, M. del Carme; Balcázar Navarro, José Luis; Jenner, Birgit (1991-11)
      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 ...
    • An approach to correctness of data parallel algorithms 

      Gabarró Vallès, Joaquim; Gavaldà Mestre, Ricard (1991-05)
      External research report
      Open Access
      The design of data parallel algorithms for fine-grained SIMD machines is a fundamental domain in today computer science. High standards in the specification and resolution of problems have been achieved in the sequential ...
    • A positive relativization of polynomial time vs. polylog space 

      Gavaldà Mestre, Ricard (1991-05)
      External research report
      Open Access
      Can every set in P be solved in polylogarithmic space? We show that this question is equivalent to asking whether the classes PSPACE and EXPTIME are always equal under relativization. We use an oracle access mechanism that ...
    • Adaptive logspace and depth-bounded reducibilities 

      Balcázar Navarro, José Luis (1991-04)
      External research report
      Open Access
      We discuss a number of results regarding an important subject: the study of the computational power of depth-bounded reducibilities, their use to classify the complexity of computational problems, and their characterizations ...
    • Characterizations of some complexity classes between [theta sub 2 super p] and [delta sub 2 super p] 

      Castro Rabal, Jorge; Seara Ojea, Carlos (1990)
      External research report
      Open Access
      We give some characterizations of the classes P super NP [0(log super k n)]. First, we show that these classes are equal to classes AC super k-1 (N P). Second, we prove that they are also equivalent to some classes defined ...
    • 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 ...
    • 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 ...
    • 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 ...
    • Parallel complexity in the design and analysis of concurrent systems 

      Álvarez Faura, M. del Carme; Balcázar Navarro, José Luis; Gabarró Vallès, Joaquim (1990-10)
      External research report
      Open Access
      We study the parallel complexity of three problems on concurrency: decision of firing sequences for Petri nets, trace equivalence for partially commutative monoids, and strong bisimilarity in finite transition systems. We ...
    • 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 ...
    • 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 ...
    • Logarithmic advice classes 

      Balcázar Navarro, José Luis; Schöning, Uwe (1988)
      External research report
      Open Access
      Karp and Lipton [9] introduced the notion of non-uniform complexity classes where a certain amount of "side information", the advice, is given for free. The advice only depends on the length of the input. Karp and Lipton ...