Solving the Ghost-Gluon System of Yang-Mills Theory on GPUs

We solve the ghost-gluon system of Yang-Mills theory using Graphics Processing Units (GPUs). Working in Landau gauge, we use the Dyson-Schwinger formalism for the mathematical description as this approach is well-suited to directly benefit from the computing power of the GPUs. With the help of a Chebyshev expansion for the dressing functions and a subsequent appliance of a Newton-Raphson method, the non-linear system of coupled integral equations is linearized. The resulting Newton matrix is generated in parallel using OpenMPI and CUDA(TM). Our results show, that it is possible to cut down the run time by two orders of magnitude as compared to a sequential version of the code. This makes the proposed techniques well-suited for Dyson-Schwinger calculations on more complicated systems where the Yang-Mills sector of QCD serves as a starting point. In addition, the computation of Schwinger functions using GPU devices is studied.Comment: 19 pages, 7 figures, additional figure added, dependence on block-size is investigated in more detail, version accepted by CP

Guiding Dynamic Symbolic Execution Toward Unverified Program Executions

Most techniques to detect program errors, such as testing, code reviews, and static program analysis, do not fully verify all possible executions of a program. They leave executions unverified when they do not check certain properties, fail to verify properties, or check properties under certain unsound assumptions such as the absence of arithmetic overflow. In this paper, we present a technique to complement partial verification results by automatic test case generation. In contrast to existing work, our technique supports the common case that the verification results are based on unsound assumptions. We annotate programs to reflect which executions have been verified, and under which assumptions. These annotations are then used to guide dynamic symbolic execution toward unverified program executions. Our main technical contribution is a code instrumentation that causes dynamic symbolic execution to abort tests that lead to verified executions, to prune parts of the search space, and to prioritize tests that cover more properties that are not fully verified. We have implemented our technique for the .NET static analyzer Clousot and the dynamic symbolic execution tool Pex. It produces smaller test suites (by up to 19.2%), covers more unverified executions (by up to 7.1%), and reduces testing time (by up to 52.4%) compared to combining Clousot and Pex without our technique

Test generation for high coverage with abstraction refinement and coarsening (ARC)

Testing is the main approach used in the software industry to expose failures. Producing thorough test suites is an expensive and error prone task that can greatly benefit from automation. Two challenging problems in test automation are generating test input and evaluating the adequacy of test suites: the first amounts to producing a set of test cases that accurately represent the software behavior, the second requires defining appropriate metrics to evaluate the thoroughness of the testing activities. Structural testing addresses these problems by measuring the amount of code elements that are executed by a test suite. The code elements that are not covered by any execution are natural candidates for generating further test cases, and the measured coverage rate can be used to estimate the thoroughness of the test suite. Several empirical studies show that test suites achieving high coverage rates exhibit a high failure detection ability. However, producing highly covering test suites automatically is hard as certain code elements are executed only under complex conditions while other might be not reachable at all. In this thesis we propose Abstraction Refinement and Coarsening (ARC), a goal oriented technique that combines static and dynamic software analysis to automatically generate test suites with high code coverage. At the core of our approach there is an abstract program model that enables the synergistic application of the different analysis components. In ARC we integrate Dynamic Symbolic Execution (DSE) and abstraction refinement to precisely direct test generation towards the coverage goals and detect infeasible elements. ARC includes a novel coarsening algorithm for improved scalability. We implemented ARC-B, a prototype tool that analyses C programs and produces test suites that achieve high branch coverage. Our experiments show that the approach effectively exploits the synergy between symbolic testing and reachability analysis outperforming state of the art test generation approaches. We evaluated ARC-B on industry relevant software, and exposed previously unknown failures in a safety-critical software component

A Survey on Region Extractors from Web Documents

Extracting information from web documents has become a research area in which new proposals sprout out year after year. This has motivated several researchers to work on surveys that attempt to provide an overall picture of the many existing proposals. Unfortunately, none of these surveys provide a complete picture, because they do not take region extractors into account. These tools are kind of preprocessors, because they help information extractors focus on the regions of a web document that contain relevant information. With the increasing complexity of web documents, region extractors are becoming a must to extract information from many websites. Beyond information extraction, region extractors have also found their way into information retrieval, focused web crawling, topic distillation, adaptive content delivery, mashups, and metasearch engines. In this paper, we survey the existing proposals regarding region extractors and compare them side by side.Ministerio de Educación y Ciencia TIN2007-64119Junta de Andalucía P07-TIC-2602Junta de Andalucía P08- TIC-4100Ministerio de Ciencia e Innovación TIN2008-04718-EMinisterio de Ciencia e Innovación TIN2010-21744Ministerio de Economía, Industria y Competitividad TIN2010-09809-EMinisterio de Ciencia e Innovación TIN2010-10811-EMinisterio de Ciencia e Innovación TIN2010-09988-

A Survey of Symbolic Execution Techniques

Many security and software testing applications require checking whether certain properties of a program hold for any possible usage scenario. For instance, a tool for identifying software vulnerabilities may need to rule out the existence of any backdoor to bypass a program's authentication. One approach would be to test the program using different, possibly random inputs. As the backdoor may only be hit for very specific program workloads, automated exploration of the space of possible inputs is of the essence. Symbolic execution provides an elegant solution to the problem, by systematically exploring many possible execution paths at the same time without necessarily requiring concrete inputs. Rather than taking on fully specified input values, the technique abstractly represents them as symbols, resorting to constraint solvers to construct actual instances that would cause property violations. Symbolic execution has been incubated in dozens of tools developed over the last four decades, leading to major practical breakthroughs in a number of prominent software reliability applications. The goal of this survey is to provide an overview of the main ideas, challenges, and solutions developed in the area, distilling them for a broad audience. The present survey has been accepted for publication at ACM Computing Surveys. If you are considering citing this survey, we would appreciate if you could use the following BibTeX entry: http://goo.gl/Hf5FvcComment: This is the authors pre-print copy. If you are considering citing this survey, we would appreciate if you could use the following BibTeX entry: http://goo.gl/Hf5Fv

Técnicas de prueba avanzadas para la generación de casos de prueba

Software testing is a crucial phase in software development, particularly in contexts such as critical systems, where even minor errors can have severe consequences. The advent of Industry 4.0 brings new challenges, with software present in almost all industrial systems. Overcoming technical limitations, as well as limited development times and budgets, is a major challenge that software testing faces nowadays. Such limitations can result in insufficient attention being paid to it. The Bay of Cadiz’s industrial sector is known for its world-leading technological projects, with facilities and staff fully committed to innovation. The close relationship between these companies and the University of Cadiz allows for a constant exchange between industry and academia. This PhD thesis aims to identify the most important elements of software testing in Industry 4.0, based on close industrial experience and the latest state-of-the-art work. This allows us to break down the software testing process in a context where large teams work on large-scale, changing projects with numerous dependencies. It also allows us to estimate the percentage benefit that a solution could provide to test engineers throughout the process. Our results indicate a need for non-commercial, flexible, and adaptable solutions for the automation of software testing, capable of meeting the constantly changing needs of industry projects. This work provides a comprehensive study on the industry’s needs and motivates the development of two new solutions using state-of-the-art technologies, which are rarely present in industrial work. These results include a tool, ASkeleTon, which implements a procedure for generating test harnesses based on the Abstract Syntax Tree (AST) and a study examining the ability of the Dynamic Symbolic Execution (DSE) testing technique to generate test data capable of detecting potential faults in software. This study leads to the creation of a novel family of testing techniques, called mutationinspired symbolic execution (MISE), which combines DSE with mutation testing (MT) to produce test data capable of detecting more potential faults than DSE alone. The findings of this work can serve as a reference for future research on software testing in Industry 4.0. The solutions developed in this PhD thesis are able to automate essential tasks in software testing, resulting in significant potential benefits. These benefits are not only for the industry, but the creation of the new family of testing techniques also represents a promising line of research for the scientific community, benefiting all software projects regardless of their field of application.La prueba del software es una de las etapas más importantes durante el desarrollo de software, especialmente en determinados tipos de contextos como el de los sistemas críticos, donde el más mínimo fallo puede conllevar la más grave de las consecuencias. Nuevos paradigmas tecnológicos como la Industria 4.0 conllevan desafíos que nunca antes se habían planteado, donde el software está presente en prácticamente todos los sistemas industriales. Uno de los desafíos más importantes a los que se enfrenta la prueba del software consiste en superar las limitaciones técnicas además de los tiempos de desarrollo y presupuestos limitados, que provocan que en ocasiones no se le preste la atención que merece. El tejido industrial de la Bahía de Cádiz es conocido por sacar adelante proyectos tecnológicos punteros a nivel mundial, con unas instalaciones y un personal totalmente implicado con la innovación. Las buenas relaciones de este conjunto de empresas con la Universidad de Cádiz, sumadas a la cercanía geográfica, permiten que haya una conversación constante entre la industria y la academia. Este trabajo de tesis persigue identificar los elementos más importantes del desarrollo de la prueba del software en la Industria 4.0 en base a una experiencia industrial cercana, además de a los últimos trabajos del estado del arte. Esto permite identificar cada etapa en la que se desglosa la prueba del software en un contexto donde trabajan equipos muy grandes con proyectos de gran envergadura, cambiantes y con multitud de dependencias. Esto permite, además, estimar el porcentaje de beneficio que podría suponer una solución que ayude a los ingenieros de prueba durante todo el proceso. Gracias a los resultados de esta experiencia descubrimos que existe la necesidad de soluciones para la automatización de la prueba del software que sean no comerciales, flexibles y adaptables a las constantes necesidades cambiantes entre los proyectos de la industria. Este trabajo aporta un estudio completo sobre las necesidades de la industria en relación a la prueba del software. Los resultados motivan el desarrollo de dos nuevas soluciones que utilizan tecnologías del estado del arte, ampliamente usadas en trabajos académicos, pero raramente presentes en trabajos industriales. En este sentido, se presentan dos resultados principales que incluyen una herramienta que implementa un procedimiento para la generación de arneses de prueba basada en el Árbol de Sintaxis Abstracta (AST) a la que llamamos ASkeleTon y un estudio donde se comprueba la capacidad de la técnica de pruebas Ejecución Simbólica Dinámica (DSE, por sus siglas en inglés) para generar datos de prueba capaces de detectar fallos potenciales en el software. Este estudio deriva en la creación de una novedosa familia de técnicas de prueba a la que llamamos mutation-inspired symbolic execution (MISE) que combina DSE con la prueba de mutaciones (MT, por sus siglas en inglés) para conseguir un conjunto de datos de prueba capaz de detectar más fallos potenciales que DSE por sí sola. Las soluciones desarrolladas en este trabajo de tesis son capaces de automatizar parte de la prueba del software, resultando en unos beneficios potenciales importantes. No solo se aportan beneficios a la industria, sino que la creación de la nueva familia de técnicas de prueba supone una línea de investigación prometedora para la comunidad científica, siendo beneficiados todos los proyectos software independientemente de su ámbito de aplicación

Secure Routing in Wireless Mesh Networks

Wireless mesh networks (WMNs) have emerged as a promising concept to meet the challenges in next-generation networks such as providing flexible, adaptive, and reconfigurable architecture while offering cost-effective solutions to the service providers. Unlike traditional Wi-Fi networks, with each access point (AP) connected to the wired network, in WMNs only a subset of the APs are required to be connected to the wired network. The APs that are connected to the wired network are called the Internet gateways (IGWs), while the APs that do not have wired connections are called the mesh routers (MRs). The MRs are connected to the IGWs using multi-hop communication. The IGWs provide access to conventional clients and interconnect ad hoc, sensor, cellular, and other networks to the Internet. However, most of the existing routing protocols for WMNs are extensions of protocols originally designed for mobile ad hoc networks (MANETs) and thus they perform sub-optimally. Moreover, most routing protocols for WMNs are designed without security issues in mind, where the nodes are all assumed to be honest. In practical deployment scenarios, this assumption does not hold. This chapter provides a comprehensive overview of security issues in WMNs and then particularly focuses on secure routing in these networks. First, it identifies security vulnerabilities in the medium access control (MAC) and the network layers. Various possibilities of compromising data confidentiality, data integrity, replay attacks and offline cryptanalysis are also discussed. Then various types of attacks in the MAC and the network layers are discussed. After enumerating the various types of attacks on the MAC and the network layer, the chapter briefly discusses on some of the preventive mechanisms for these attacks.Comment: 44 pages, 17 figures, 5 table