Chaining Test Cases for Reactive System Testing (extended version)

Testing of synchronous reactive systems is challenging because long input sequences are often needed to drive them into a state at which a desired feature can be tested. This is particularly problematic in on-target testing, where a system is tested in its real-life application environment and the time required for resetting is high. This paper presents an approach to discovering a test case chain---a single software execution that covers a group of test goals and minimises overall test execution time. Our technique targets the scenario in which test goals for the requirements are given as safety properties. We give conditions for the existence and minimality of a single test case chain and minimise the number of test chains if a single test chain is infeasible. We report experimental results with a prototype tool for C code generated from Simulink models and compare it to state-of-the-art test suite generators.Comment: extended version of paper published at ICTSS'1

Sound Static Deadlock Analysis for C/Pthreads (Extended Version)

We present a static deadlock analysis approach for C/pthreads. The design of our method has been guided by the requirement to analyse real-world code. Our approach is sound (i.e., misses no deadlocks) for programs that have defined behaviour according to the C standard, and precise enough to prove deadlock-freedom for a large number of programs. The method consists of a pipeline of several analyses that build on a new context- and thread-sensitive abstract interpretation framework. We further present a lightweight dependency analysis to identify statements relevant to deadlock analysis and thus speed up the overall analysis. In our experimental evaluation, we succeeded to prove deadlock-freedom for 262 programs from the Debian GNU/Linux distribution with in total 2.6 MLOC in less than 11 hours

Computerspielen als medial-kulturelle Praktik - Ein medienpädagogisch-kulturtheoretischer Zugang zum Phänomen Computerspielen

Gegenwärtig werden im medienpädagogischen Diskurs Computerspiele primär als Medienangebote thematisiert, wobei oftmals ausser Acht gelassen wird, dass Spielen eine kulturell geprägte, aktive und soziale Auseinandersetzung mit dem Spiel als Artefakt, Regelwerk und Geschichte impliziert. Im vorliegenden Beitrag wird vor dem Hintergrund bildungstheoretischer und lerntheoretischer Überlegungen ein methodisch-theoretischer Zugang entfaltet und präzisiert, der es erlaubt, Computerspiele als spezifisch situierte medial-kulturelle Praktik pädagogisch zu erfassen, zu beschreiben und zu analysieren. Werden Computerspiele und ihr Spielen als Transformation und Produktion von kulturellen Erfahrungen thematisiert, dann stellt sich die Frage nach der pädagogischen Dimension des Computerspiel(en)s neu. Es eröffnet sich dabei ein Forschungsfeld, das nach differenzierter medienpädagogischer Herangehensweise verlangt. Der vorliegende medienpädagogisch-kulturtheoretische Zugang zum Phänomen Computerspielen baut auf den theoretischen Wurzeln der Spieleforschung auf und fasst das Spielen als medial-kulturelle Handlung

Challenges in decomposing encodings of verification problems

Modern program verifiers use logic-based encodings of the verification problem that are discharged by a back end reasoning engine. However, instances of such encodings for large programs can quickly overwhelm these back end solvers. Hence, we need techniques to make the solving process scale to large systems, such as partitioning (divide-and-conquer) and abstraction. In recent work, we showed how decomposing the formula encoding of a termination analysis can significantly increase efficiency. The analysis generates a sequence of logical formulas with existentially quantified predicates that are solved by a synthesis-based program analysis engine. However, decomposition introduces abstractions in addition to those required for finding the unknown predicates in the formula, and can hence deteriorate precision. We discuss the challenges associated with such decompositions and their interdependencies with the solving process

Abstract Acceleration in Linear relation analysis (extended version)

Linear relation analysis is a classical abstract interpretation based on an over-approximation of reachable numerical states of a program by convex polyhedra. Since it works with a lattice of infinite height, it makes use of a widening operator to enforce the convergence of fixed point computations. Abstract acceleration is a method that computes the precise abstract effect of loops wherever possible and uses widening in the general case. Thus, it improves both the precision and the efficiency of the analysis. This research report gives a comprehensive tutorial on abstract acceleration: its origins in Presburger-based acceleration including new insights w.r.t. the linear accelerability of linear transformations, methods for simple and nested loops, recent extensions, tools and applications, and a detailed discussion of related methods and future perspectives. This is the long version of a paper under submission

Utilização de ferramentas de SIG para Agricultura de Precisão no planejamento ambiental de uma pequena propriedade rural produtora de maçãs.

O uso de ferramentas de SIG e a agricultura de precisão sempre estiveram vinculados à idéia de grandes empreendimentos agropecuários. Inicialmente o custo das ferramentas e insumos necessários tornava proibitivo seu uso em pequenas propriedades. Com o avanço do conhecimento das técnicas de coleta e organização de dados, e o barateamento das ferramentas de organização (computadores, planilhas eletrônicas, imagens de satélite), além da existência de softwares de geoprocessamento e SIG livres e com interface amigável, a barreira para o uso desta técnica também para a pequena propriedade passou a ser possível. O objetivo deste trabalho é verificar se é possível ao pequeno produtor aplicar os princípios da agricultura de precisão através da aplicação de ferramentas de SIG, através da obtenção, organização e manuseio de informações livres ou de baixo custo