New Deterministic Algorithms for Solving Parity Games

We study parity games in which one of the two players controls only a small number $k$ of nodes and the other player controls the $n-k$ other nodes of the game. Our main result is a fixed-parameter algorithm that solves bipartite parity games in time $k^{O(\sqrt{k})}\cdot O(n^3)$, and general parity games in time $(p+k)^{O(\sqrt{k})} \cdot O(pnm)$, where $p$ is the number of distinct priorities and $m$ is the number of edges. For all games with $k = o(n)$ this improves the previously fastest algorithm by Jurdzi{\'n}ski, Paterson, and Zwick (SICOMP 2008). We also obtain novel kernelization results and an improved deterministic algorithm for graphs with small average degree

Symmetric Strategy Improvement

Symmetry is inherent in the definition of most of the two-player zero-sum games, including parity, mean-payoff, and discounted-payoff games. It is therefore quite surprising that no symmetric analysis techniques for these games exist. We develop a novel symmetric strategy improvement algorithm where, in each iteration, the strategies of both players are improved simultaneously. We show that symmetric strategy improvement defies Friedmann's traps, which shook the belief in the potential of classic strategy improvement to be polynomial

Checking Properties Described by State Machines: On Synergy of Instrumentation, Slicing, and Symbolic Execution

We introduce a novel technique for checking properties described by finite state machines. The technique is based on a synergy of three well-known methods: instrumentation, program slicing, and symbolic execution. More precisely, we instrument a given program with a code that tracks runs of state machines representing various properties. Next we slice the program to reduce its size without affecting runs of state machines. And then we symbolically execute the sliced program to find real violations of the checked properties, i.e. real bugs. Depending on the kind of symbolic execution, the technique can be applied as a stand-alone bug finding technique, or to weed out some false positives from an output of another bug-finding tool. We provide several examples demonstrating the practical applicability of our technique.Představujeme novou techniku pro ověřování vlastností popsaných konečně-stavovými stroji. Tato technika je založena na synergii tří známých metod: instrumentace, prořezání programu a symbolické vykonání. Přesněji, instrumentujeme daný program kódem, který sleduje běh stavových strojů představujících různé vlastnosti. Dále program prořežeme, abychom zmenšili jeho velikost při zachování běhů stavových strojů. Nakonec prořezaný program symbolicky vykonáme, abychom našli skutečné porušení ověřovaných vlastností, t.j. skutečné chyby. Podle použitého druhu symbolického vykonání může být tato technika použita jako samostatná metoda pro detekci chyb nebo k vytřídění některých falešných hlášení z výstupu jiných nástrojů pro detekci chyb. Poskytujeme několik příkladů, které dokumentují praktickou použitelnost naší techniky

Parity Games of Bounded Tree- and Clique-Width

Abstract. In this paper it is shown that deciding the winner of a parity game is in LogCFL, if the underlying graph has bounded tree-width, and in LogDCFL, if the tree-width is at most 2. It is also proven that parity games of bounded clique-width can be solved in LogCFL via a log-space reduction to the bounded tree-width case, assuming that a k-expression for the parity game is part of the input.

LNCS

Discrete-time Markov Chains (MCs) and Markov Decision Processes (MDPs) are two standard formalisms in system analysis. Their main associated quantitative objectives are hitting probabilities, discounted sum, and mean payoff. Although there are many techniques for computing these objectives in general MCs/MDPs, they have not been thoroughly studied in terms of parameterized algorithms, particularly when treewidth is used as the parameter. This is in sharp contrast to qualitative objectives for MCs, MDPs and graph games, for which treewidth-based algorithms yield significant complexity improvements. In this work, we show that treewidth can also be used to obtain faster algorithms for the quantitative problems. For an MC with n states and m transitions, we show that each of the classical quantitative objectives can be computed in O((n+m)⋅t2) time, given a tree decomposition of the MC with width t. Our results also imply a bound of O(κ⋅(n+m)⋅t2) for each objective on MDPs, where κ is the number of strategy-iteration refinements required for the given input and objective. Finally, we make an experimental evaluation of our new algorithms on low-treewidth MCs and MDPs obtained from the DaCapo benchmark suite. Our experiments show that on low-treewidth MCs and MDPs, our algorithms outperform existing well-established methods by one or more orders of magnitude

O expletivo ele em domínios dependentes em português europeu

Tese de mestrado, Linguística, Universidade de Lisboa, Faculdade de Letras, 2013Esta dissertação tem como objeto de estudo a distribuição do expletivo ele nãopadrão em domínios oracionais dependentes em português europeu. Partindo de uma caracterização do expletivo ele como elemento linguístico relacionado com posições sintáticas na periferia esquerda da frase, a investigação aqui apresentada centra-se sobre a descrição sintática dos contextos dependentes que envolvem este expletivo, a fim de verificar: a posição ocupada por ele na periferia esquerda de domínios oracionais nãomatriz, a ocorrência de simetrias/assimetrias na distribuição e nos efeitos discursivos do expletivo em orações dependentes relativamente às propriedades atribuídas a este expletivo em orações principais. Neste sentido, a presente investigação visa também contribuir para o estudo comparativo da estrutura da periferia esquerda em frases principais e em frases dependentes. A base empírica aqui apresentada incide sobre dados de variedades não-padrão do português europeu recolhidos do Corpus Dialectal para o Estudo da Sintaxe (CORDIAL-SIN), desenvolvido pelo Centro de Linguística da Universidade de Lisboa. No plano da distribuição sintática, em orações dependentes, dois tipos de expletivo são distinguidos: o expletivo pré-verbal, que ocorre em posição pré ou pósconector e que pode ser associado a uma projeção ForceP na periferia esquerda da estrutura frásica, ou no domínio da oração dependente ou no domínio matriz de uma oração dependente periférica; pontualmente, o expletivo pós-verbal, que aparece em uma posição mais baixa. A presença do expletivo ele em contextos não-matriz manifesta propriedades discursivas enfáticas relevantes para a codificação de efeitos ilocutórios, em muitos dos exemplos analisados associáveis a domínios dependentes assertivos.Abstract The object of the study in this dissertation consists of the distribution of nonstandard expletive ele in dependent clausal domains in European Portuguese. Based on a characterization of the expletive ele as a linguistic element related to syntactic positions on the left periphery of the sentence, the research presented here focuses on the syntactical description of dependents contexts involving this expletive, in order to examine: the position occupied by ele in left periphery of non matrix clausal domains, the occurrence of symmetry/asymmetry in the distribution and discursive effects of the expletive in dependent clauses regarding the properties attributed to this expletive in main clauses. In this sense, this research also aims to contribute to the comparative study of the left periphery structure in main clauses and dependents phrases. The empirical study presented here focuses on non-standard European Portuguese data collected from the Syntax-oriented Corpus of Portuguese Dialects (CORDIAL-SIN), developed by the Centro de Linguística da Universidade de Lisboa. In terms of syntactic distribution, in dependents clauses, two expletive types are distinguished: the preverbal expletive, which occurs in a pre or post-connector position and can be associated with a ForceP projection in the left periphery of the sentence, either in dependents clauses or in the matrix clause domain of a peripheral dependent clause; and, occasionally, a post verbal expletive, which appears in a lower position. The presence of the expletive ele in non-matrix contexts shows discursive properties relevant to codify illocutionary effects, and in many examples it can be associated with assertive dependents domains

Gap – gep – gap?

They presented the general terminological difficulties in technical language continuum physics. In particular it deals with the advantages and disadvantages of the great influence of English in terms of graphical (typological) and phoneti

FO model checking of interval graphs

We study the computational complexity of the FO model checking problem on interval graphs, i.e., intersection graphs of intervals on the real line. The main positive result is that this problem can be solved in time O(n logn) for n-vertex interval graphs with representations containing only intervals with lengths from a prescribed finite set. We complement this result by showing that the same is not true if the lengths are restricted to any set that is dense in some open subset, e.g., in the set (1, 1 + ε)

New Deterministic Algorithms for Solving Parity Games

We study parity games in which one of the two players controls only a small number k of nodes and the other player controls the n-k n-kn-k other nodes of the game. Our main result is a fixed-parameter algorithm that solves bipartite parity games in time k o(k v ) ·o(n 3 ) ko(k)·o(n3)k^{o(\sqrt{k})}\cdot o(n^3) and general parity games in time (p+k) o(k v ) ·o(pnm) (p+k)o(k)·o(pnm)(p+k)^{o(\sqrt{k})} \cdot o(pnm), where p denotes the number of distinct priorities and m denotes the number of edges. For all games with k=o(n) k=o(n)k = o(n) this improves the previously fastest algorithm by jurdzinski, paterson, and zwick (sicomp 2008).we also obtain novel kernelization results and an improved deterministic algorithm for graphs with small average degree

The methodology of mapping, evidence, documentation, care, and protection of important avenues and their trees

Práce zahrnuje úvodní obecnou analytickou část, jejímž účelem je stručné informativní shrnutí současného poznání a komplexní podstaty řešené alejové problematiky. Na tuto část navazují konkrétní kapitoly v rámci odborné aplikované části: Mapování a dokumentace alejí (popisující stanovené a odzkoušené metody mapování, dokumentace a evidence sledovaných jevů a prvků významných alejových linií a stromořadí v krajině), Množení alejových dřevin (kde jsou rozebrány vhodné metody přemnožení vybraných alejových dřevin, péče o ně a jejich další pěstování) a Obnova a management historických alejí (kde jsou popsány jak současné postupy a principy péče a ochrany alejí a jejich dřevin, tak i používané metody (včetně zahraničních) revitalizací a obnov, které jsou významné z hlediska současné praxe)