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String Constraint Solving Through Parikh Images
Bartoš, Petr ; Havlena, Vojtěch (oponent) ; Holík, Lukáš (vedoucí práce)
This bachelor thesis aims to implement an alternative way of solving string constraints using the so-called flattening algorithm. The algorithm makes use of Parikh images and parametric flat automata to effectively convert string constraints to linear arithmetic, which allows for leveraging powerful SMT solvers. Solving constraints as an algebraic problem is supposed to be more efficient than standardly used automata-based techniques, as it avoids common pitfalls, such as state-space exposion. The thesis covers the theoretical knowledge required to understand the flattening algorithm and introduces alternative modern solution strategies. The implementation results are then compared to other solvers using conventional competition benchmarks. The conducted experiments show that while the speed of the implementation compared to other state-of-the-art solvers is worse, the effectiveness of the underapproximation itself is fairly promising, thus yielding mixed results.
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Abstraction of State Languages in Automata Algorithms
Chocholatý, David ; Síč, Juraj (oponent) ; Holík, Lukáš (vedoucí práce)
We explore possibilities of using various abstractions of finite automata languages in optimization of automata algorithms used in automata reasoning. We focus on abstracting languages of states to sets of accepted lengths of word or Parikh images, represented as semi-linear sets, and explore options of using them to optimize automata constructions by pruning states based on abstractions of their languages. We propose several abstractions and work on optimizing their performance. We use two common finite automata problems, synchronous product construction and deciding the emptiness of finite automata intersection, as benchmark problems on which we test our optimizations. Nevertheless, our abstractions are applicable on many other typical automata operations, e.g., complement generation etc. Our experiments show that the proposed optimizations reduce generated state space for both benchmark problems substantially.
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Abstraction of State Languages in Automata Algorithms
Chocholatý, David ; Síč, Juraj (oponent) ; Holík, Lukáš (vedoucí práce)
We explore possibilities of using various abstractions of finite automata languages in optimization of automata algorithms used in automata reasoning. We focus on abstracting languages of states to sets of accepted lengths of word or Parikh images, represented as semi-linear sets, and explore options of using them to optimize automata constructions by pruning states based on abstractions of their languages. We propose several abstractions and work on optimizing their performance. We use two common finite automata problems, synchronous product construction and deciding the emptiness of finite automata intersection, as benchmark problems on which we test our optimizations. Nevertheless, our abstractions are applicable on many other typical automata operations, e.g., complement generation etc. Our experiments show that the proposed optimizations reduce generated state space for both benchmark problems substantially.
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