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Applying formal methods to analysis of semantic differences between versions of software
Nečas, František ; Vojnar, Tomáš (oponent) ; Malík, Viktor (vedoucí práce)
The goal of this work is to propose an integration of formal methods into DiffKemp, a static analysis tool for analyzing semantic differences of large-scale C projects. The aim of this extension is to facilitate analysis of more complex code changes, which would typically be better handled by a tool based on formal methods, while also maintaining DiffKemp’s scalability to large projects. To achieve this, whenever a possible semantic change is found, the equivalence of the relevant instructions is encoded into an SMT problem instance and the difference is either confirmed or refuted using an SMT solver. The proposed solution has been implemented in DiffKemp and our experiments on a set of benchmarks called EqBench show that it extends the capabilities of DiffKemp, mainly with regards to sound analysis of refactorings of arithmetic expressions.
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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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Generic Template-Based Synthesis of Program Abstractions
Marušák, Matej ; Holík, Lukáš (oponent) ; Malík, Viktor (vedoucí práce)
The goal of this work is to design and to implement a generic strategy solver to the 2LS tool. 2LS is an analyser for a static verification of programs written in C language. A verified program is analysed by an SMT solver using abstract interpretation. Convertion from an abstract state of the program into a logical formula, that an SMT solver can work with, is done by a component called strategy solver. In the current implementation, there is one strategy solver for each abstract domain. Our approach introduces a single generic strategy solver, which makes creating new domains easier. Also, this approach enables migration of the existing domains and hence the codebase can be reduced.
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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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Generic Template-Based Synthesis of Program Abstractions
Marušák, Matej ; Holík, Lukáš (oponent) ; Malík, Viktor (vedoucí práce)
The goal of this work is to design and to implement a generic strategy solver to the 2LS tool. 2LS is an analyser for a static verification of programs written in C language. A verified program is analysed by an SMT solver using abstract interpretation. Convertion from an abstract state of the program into a logical formula, that an SMT solver can work with, is done by a component called strategy solver. In the current implementation, there is one strategy solver for each abstract domain. Our approach introduces a single generic strategy solver, which makes creating new domains easier. Also, this approach enables migration of the existing domains and hence the codebase can be reduced.
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