Rastislav Lenhardt

Learn More
Gipfeli is a high-speed compression algorithm that uses backward references with a 16-bit sliding window, based on 1977 paper by Lempel and Ziv, enriched with an ad-hoc entropy coding for both literals and backward references. We have implemented it in C++ and fine-tuned for very high performance. The compression ratio is similar to Zlib in the fastest(More)
Interval Markov chains (IMCs) generalize ordinary Markov chains by having interval-valued transition probabilities. They are useful for modeling systems in which some transition probabilities depend on an unknown environment, are only approximately known, or are parameters that can be controlled. We consider the problem of computing values for the unknown(More)
Verification of properties expressed in the two-variable fragment of first-order logic FO<sup>2</sup> has been investigated in a number of contexts. The satisfiability problem for FO<sup>2</sup> over arbitrary structures is known to be NEXPTIME-complete, with satisfiable formulas having exponential-sized models. Over words, where FO<sup>2</sup> is known to(More)
An automaton is unambiguous if each word has at most one accepting run and separated if no word is accepted from two distinct states. The classical translation of LTL formulas to Büchi automata [5] produces unambiguous separated automata since the states of such automata correspond to complete subformula types. Motivated by this observation, Couvreur et al.(More)
Verification of properties of first order logic with two variables FO has been investigated in a number of contexts. Over arbitrary structures it is known to be decidable with NEXPTIME complexity, with finitely satisfiable formulas having exponential-sized models. Over word structures, where FO is known to have the same expressiveness as unary temporal(More)
Probabilistic automata were introduced by Rabin in early 1960s. We extend this concept by allowing transition probabilities among the states to be parametric. Two main decision problems are considered: the language equivalence and bisimulation of probabilistic automata. One of our main results is a new one sided error Monte Carlo randomized polynomial-time(More)
In the last decade, the power of the state-of-the-art SAT and ILP (Integer Linear Programming) solvers has dramatically increased. They implement many new techniques and heuristics and since any NP problem can be converted to SAT or ILP instance, we could take advantage of these techniques in general by converting the instance of NP problem to SAT formula(More)
  • 1