A Preliminary Analysis on the Effect of Randomness in a CEGAR Framework

Formal verification techniques can check the correctness of systems in a mathematically precise way. Counterexample-Guided Abstraction Refinement (CEGAR) is an automatic algorithm that reduces the complexity of systems by constructing and refining abstractions. CEGAR is a generic approach, having many variants and strategies developed over the years. However, as the variants become more and more advanced, one may not be sure whether the performance of a strategy can be attributed to the strategy itself or to other, unintentional factors. In this paper we perform an experiment by evaluating the performance of different strategies while randomizing certain external factors such as the search strategy and variable naming. We show that randomization introduces a great variation in the output metrics, and that in several cases this might even influence whether the algorithm successfully terminates

Exploratory Analysis of the Performance of a Configurable CEGAR Framework

Formal verification techniques can check the correctness of systems in a mathematically precise way. However, their computational complexity often prevents their successful application. The counterexample-guided abstraction refinement (CEGAR) algorithm aims to overcome this problem by automatically building abstractions for the system to reduce its complexity. Previously, we developed a generic CEGAR framework, which incorporates many configurations of the algorithm. In this paper we focus on an exploratory analysis of our framework. We identify parameters of the systems and algorithm configurations, overview some possible analysis methods and present preliminary results. We show that different variants are more efficient for certain tasks and we also describe how the properties of the system and parameters of the algorithm affect the success of verification

Supporting Unit Test Generation via Automated Isolation

“Este trabajo es una compilación de crónicas, resultado del programa Talleres de Crónica Memorias del Agua, auspiciado por el Banco de la República bajo la coordinación académica de la Pontificia Universidad Javeriana, que pretende contar una historia inédita del país inspirada por el agua. Las setenta y cuatro crónicas seleccionadas para este libro permitieron concluir que, en el nuevo milenio, en varias capitales y cabeceras municipales del país, hay miles de personas que libran una batalla diaria por acceder a este recurso básico. Estos talleres propiciaron un estimulante diálogo entre culturas regionales, generaciones, oficios, saberes, disciplinas y miradas al agua en medio de la diversidad territorial. La mayoría de los participantes jamás había escrito una crónica, y los que tenían experiencia con la escritura no habían experimentado con ese género. Otros comprendieron la desaprovechada cercanía entre la historia y el periodismo, el periodismo y la literatura. En los talleres aprendieron a encontrar su propia voz y a recoger las voces de otros para lograr esa polifonía que pide el género”. Descripción tomada de la sección de novedades de publicaciones de la Pontificia Universidad Javeriana. http://www.javeriana.edu.co/editorial/libros/pais-gota-agua- Memorias. - Lugares. - Personajes

To Do or Not to Do: Semantics and Patterns for Do Activities in UML PSSM State Machines

State machines are used ubiquitously in engineering software-intensive systems. UML State Machines extend simple finite state machines with powerful constructs. Among the many extensions, there is one seemingly simple and innocent language construct that fundamentally changes state machines' reactive model of computation: doActivity behaviors. DoActivity behaviors describe behavior that is executed independently from the state machine once entered in a given state, typically modeling complex computation or communication as background tasks. However, the UML specification or textbooks are vague about how the doActivity behavior construct should be appropriately used. This lack of guidance is a severe issue as, when improperly used, doActivities can cause concurrent, non-deterministic bugs that are especially challenging to find and could ruin a seemingly correct software design. The Precise Semantics of UML State Machines (PSSM) specification introduced detailed operational semantics for state machines. To the best of our knowledge, there is no rigorous review yet of doActivity's semantics as specified in PSSM. We analyzed the semantics by collecting evidence from cross-checking the text of the specification, its semantic model and executable test cases, and the simulators supporting PSSM. We synthesized insights about subtle details and emergent behaviors relevant to tool developers and advanced modelers. We reported inconsistencies and missing clarifications in more than 20 issues to the standardization committee. Based on these insights, we studied 11 patterns for doActivities detailing the consequences of using a doActivity in a given situation and discussing countermeasures or alternative design choices. We hope that our analysis of the semantics and the patterns help vendors develop conformant simulators or verification tools and engineers design better state machine models

Towards Evaluating Size Reduction Techniques for Software Model Checking

Formal verification techniques are widely used for detecting design flaws in software systems. Formal verification can be done by transforming an already implemented source code to a formal model and attempting to prove certain properties of the model (e.g. that no erroneous state can occur during execution). Unfortunately, transformations from source code to a formal model often yield large and complex models, making the verification process inefficient and costly. In order to reduce the size of the resulting model, optimization transformations can be used. Such optimizations include common algorithms known from compiler design and different program slicing techniques. Our paper describes a framework for transforming C programs to a formal model, enhanced by various optimizations for size reduction. We evaluate and compare several optimization algorithms regarding their effect on the size of the model and the efficiency of the verification. Results show that different optimizations are more suitable for certain models, justifying the need for a framework that includes several algorithms.Comment: In Proceedings VPT 2017, arXiv:1708.0688

A kukoricahibridek agronómiai és környezeti reakcióinak összehasonlító vizsgálata növekedésanalízissel és ökofiziológiai mérésekkel tartamkísérletekben = Comparative studies on the agronomic and environmental responses of maize hybrids by methods of plant growth analysis and ecophysiological measurements in long-term experiments

A növekedésanalízist és az ökofiziológiai kutatásokat öt különböző kisparcellás kísérletben végeztük. Három kukoricahibrid növényszám reakcióját hat denzitásnál vizsgáltuk. A növényszám reakció komplex leírása a növényegyedek és a növényállomány produkció vizsgálatán és növekedési és ökofiziológiai paramétereken alapult. Új összefüggést találtunk a termés és a genotípusok növekedési paraméterei között. Az N műtrágyázás hatását vizsgáltuk 3 kukoricahibrid növekedésének és növekedési paramétereinek dinamikájára. Az N műtrágyázásnak szignifikáns hatása volt a szárazanyag akkumuláció és a levélterület dinamikájára. A növekedési paraméterek jól jellemezték az N stressz hatását a növekedésre és a termésképzésre. A szárazanyag akkumuláció és a növekedési paraméterek dinamikája hozzájárulhat az N műtrágya reakció időbeni változásának megértéséhez és a kukoricahibridek N hasznosításának javításához. A növekedésanalízis - ökofiziológiai mérésekkel kiegészítve - ideális módszer az agronómiai és ökológiai faktorok hatásának tanulmányozására és az agronómiai reakciók közötti genotípusos különbségek okainak feltárására. A kutatási program keretében három fiatal PhD hallgató fejezte be kutatásait. | Growth analysis and ecophysiological measurements were carried out in five different small-plot experiments. The plant density responses of 3 maize hybrids were studied at six plant densities. Detailed sudies were made on the effect of plant density on dry matter accumulation and on plant growth rate. Complex description of the plant density responses of maize hybrids was based on the yield of individual plants and plant stands and on growth and ecophysiological parameters. New relationships were found between the yield and the growth parameters of the maize plants. The effect of N fertilisation on the dynamics of growth and growth parameter dynamics of 3 maize hybrids was investigated. N fertilisation was demonstrated to have a significant effect on the dynamics of both the dry matter accumulation and leaf area of maize plants. The growth parameters gave a good characterisation of how N stress affected maize growth and yield formation. The dynamics of dry matter accumulation and of growth parameters could contribute to an understanding of changes in the N fertiliser response over time and to improvements in the N utilisation of maize hybrids. Growth analysis is an ideal method for studying the independent and interactive effects of different factors and, when supplemented by ecophysiological measurements, for discovering the causes of genotypic differences in agronomic responses. Three junior scientists were working for their PhDs within the framework of the project