383 research outputs found
Metaheuristic models for decision support in the software construction process
En la actualidad, los ingenieros software no solo tienen la responsabilidad de construir
sistemas que desempe~nen una determinada funcionalidad, sino que cada vez
es más importante que dichos sistemas también cumplan con requisitos no funcionales
como alta disponibilidad, efciencia o seguridad, entre otros. Para lograrlo,
los ingenieros se enfrentan a un proceso continuo de decisión, pues deben estudiar
las necesidades del sistema a desarrollar y las alternativas tecnológicas existentes
para implementarlo. Todo este proceso debe estar encaminado a la obtención de
sistemas software de gran calidad, reutilizables y que faciliten su mantenimiento y
modificación en un escenario tan exigente y competitivo.
La ingeniería del software, como método sistemático para la construcción de software,
ha aportado una serie de pautas y tareas que, realizadas de forma disciplinada
y adaptadas al contexto de desarrollo, posibilitan la obtención de software de calidad.
En concreto, el proceso de análisis y diseño del software ha adquirido una gran
importancia, pues en ella se concibe la estructura del sistema, en términos de sus bloques
funcionales y las interacciones entre ellos. Es en este momento cuando se toman
las decisiones acerca de la arquitectura, incluyendo los componentes que la conforman,
que mejor se adapta a los requisitos, tanto funcionales como no funcionales,
que presenta el sistema y que claramente repercuten en su posterior desarrollo. Por
tanto, es necesario que el ingeniero analice rigurosamente las alternativas existentes,
sus implicaciones en los criterios de calidad impuestos y la necesidad de establecer
compromisos entre ellos. En este contexto, los ingenieros se guían principalmente
por sus habilidades y experiencia, por lo que dotarles de métodos de apoyo a la
decisión representaría un avance significativo en el área.
La aplicación de técnicas de inteligencia artificial en este ámbito ha despertado un
gran interés en los últimos años. En particular, la inteligencia artificial ha encontrado
en la ingeniería del software un ámbito de aplicación complejo, donde diferentes
técnicas pueden ayudar a conseguir la semi-automatización de tareas tradicionalmente
realizadas de forma manual. De la unión de ambas áreas surge la denominada
ingeniería del software basada en búsqueda, que propone la reformulación de las
actividades propias de la ingeniería del software como problemas de optimización.
A continuación, estos problemas podrían ser resueltos mediante técnicas de búsqueda
como las metaheurísticas. Este tipo de técnicas se caracterizan por explorar el
espacio de posibles soluciones de una manera \inteligente", a menudo simulando
procesos naturales como es el caso de los algoritmos evolutivos.
A pesar de ser un campo de investigación muy reciente, es posible encontrar propuestas
para automatizar una gran variedad de tareas dentro del ciclo de vida del software, como son la priorización de requisitos, la planifcación de recursos, la refactorización del código fuente o la generación de casos de prueba. En el ámbito del
análisis y diseño de software, cuyas tareas requieren de creatividad y experiencia,
conseguir una automatización completa resulta poco realista. Es por ello por lo que
la resolución de sus tareas mediante enfoques de búsqueda debe ser tratada desde la
perspectiva del ingeniero, promoviendo incluso la interacción con ellos. Además, el
alto grado de abstracción de algunas de sus tareas y la dificultad de evaluar cuantitativamente
la calidad de un diseño software, suponen grandes retos en la aplicación
de técnicas de búsqueda durante las fases tempranas del proceso de construcción de
software.
Esta tesis doctoral busca realizar aportaciones significativas al campo de la ingeniería
del software basada en búsqueda y, más concretamente, al área de la optimización
de arquitecturas software. Aunque se están realizando importantes avances en este
área, la mayoría de propuestas se centran en la obtención de arquitecturas de bajo
nivel o en la selección y despliegue de artefactos software ya desarrollados. Por tanto,
no existen propuestas que aborden el modelado arquitectónico a un nivel de abstracción elevado, donde aún no existe un conocimiento profundo sobre cómo será el
sistema y, por tanto, es más difícil asistir al ingeniero. Como problema de estudio,
se ha abordado principalmente la tarea del descubrimiento de arquitecturas software
basadas en componentes. El objetivo de este problema consiste en abstraer los bloques
arquitectónicos que mejor definen la estructura actual del software, así como
sus interacciones, con el fin de facilitar al ingeniero su posterior análisis y mejora.
Durante el desarrollo de esta tesis doctoral se ha explorado el uso de una gran variedad
de técnicas de búsqueda, estudiando su idoneidad y realizando las adaptaciones
necesarias para hacer frente a los retos mencionados anteriormente. La primera propuesta
se ha centrado en la formulación del descubrimiento de arquitecturas como
problema de optimización, abordando la representación computacional de los artefactos
software que deben ser modelados y definiendo medidas software para evaluar
su calidad durante el proceso de búsqueda. Además, se ha desarrollado un primer
modelo basado en algoritmos evolutivos mono-objetivo para su resolución, el cual ha
sido validado experimentalmente con sistemas software reales. Dicho modelo se caracteriza
por ser comprensible y
exible, pues sus componentes han sido diseñados
considerando estándares y herramientas del ámbito de la ingeniería del software,
siendo además configurable en función de las necesidades del ingeniero.
A continuación, el descubrimiento de arquitecturas ha sido tratado desde una perspectiva
multiobjetivo, donde varias medidas software, a menudo en con
icto, deben
ser simultáneamente optimizadas. En este caso, la resolución del problema se ha
llevado a cabo mediante ocho algoritmos del estado del arte, incluyendo propuestas recientes del ámbito de la optimización de muchos objetivos. Tras ser adaptados al
problema, estos algoritmos han sido comparados mediante un extenso estudio experimental
con el objetivo de analizar la ifnuencia que tiene el número y la elección
de las métricas a la hora de guiar el proceso de búsqueda. Además de realizar una
validación del rendimiento de estos algoritmos siguiendo las prácticas habituales
del área, este estudio aporta un análisis detallado de las implicaciones que supone
la optimización de múltiples objetivos en la obtención de modelos de soporte a la
decisión.
La última propuesta en el contexto del descubrimiento de arquitecturas software
se centra en la incorporación de la opinión del ingeniero al proceso de búsqueda.
Para ello se ha diseñado un mecanismo de interacción que permite al ingeniero indicar
tanto las características deseables en las soluciones arquitectónicas (preferencias
positivas) como aquellos aspectos que deben evitarse (preferencias negativas). Esta
información es combinada con las medidas software utilizadas hasta el momento,
permitiendo al algoritmo evolutivo adaptar la búsqueda conforme el ingeniero interactúe. Dadas las características del modelo, su validación se ha realizado con la
participación de ingenieros con distinta experiencia en desarrollo software, a fin de
demostrar la idoneidad y utilidad de la propuesta.
En el transcurso de la tesis doctoral, los conocimientos adquiridos y las técnicas
desarrolladas también han sido extrapolados a otros ámbitos de la ingeniería del
software basada en búsqueda mediante colaboraciones con investigadores del área.
Cabe destacar especialmente la formalización de una nueva disciplina transversal,
denominada ingeniería del software basada en búsqueda interactiva, cuyo fin es promover
la participación activa del ingeniero durante el proceso de búsqueda. Además,
se ha explorado la aplicación de algoritmos de muchos objetivos a un problema clásico
de la computación orientada a servicios, como es la composición de servicios web.Nowadays, software engineers have not only the responsibility of building systems that provide a particular functionality, but they also have to guarantee that these systems ful l demanding non-functional requirements like high availability, e ciency or security. To achieve this, software engineers face a continuous decision process, as they have to evaluate system needs and existing technological alternatives to implement it. All this process should be oriented towards obtaining high-quality and reusable systems, also making future modi cations and maintenance easier in such a competitive scenario. Software engineering, as a systematic method to build software, has provided a number of guidelines and tasks that, when done in a disciplinarily manner and properly adapted to the development context, allow the creation of high-quality software. More speci cally, software analysis and design has acquired great relevance, being the phase in which the software structure is conceived in terms of its functional blocks and their interactions. In this phase, engineers have to make decisions about the most suitable architecture, including its constituent components. Such decisions are made according to the system requirements, either functional or non-functional, and will have a great impact on its future development. Therefore, the engineer has to rigorously analyse existing alternatives, their implications on the imposed quality criteria and the need of establishing trade-o s among them. In this context, engineers are mostly guided by their own capabilities and experience, so providing them with decision support methods would represent a signi cant contribution. The application of arti cial intelligent techniques in this area has experienced a growing interest in the last years. Particularly, software engineering represents a complex application domain to arti cial intelligence, whose diverse techniques can help in the semi-automation of tasks traditionally performed manually. The union of both elds has led to the appearance of search-based software engineering, which proposes reformulating software engineering activities as optimisation problems. For their resolution, search techniques like metaheuristics can be then applied. This type of technique performs an \intelligent" exploration of the space of candidate solutions, often inspired by natural processes as happens with evolutionary algorithms. Despite the novelty of this research eld, there are proposals to automate a great variety of tasks within the software lifecycle, such as requirement prioritisation, resource planning, code refactoring or test case generation. Focusing on analysis and design, whose tasks require creativity and experience, trying to achieve full automation is not realistic. Therefore, solving design tasks by means of search approaches should be oriented towards the engineer's perspective, even promoting their interaction. Furthermore, design tasks are also characterised by a high level of abstraction and the di culty of quantitatively evaluating design quality. All these aspects represent key challenges for the application of search techniques in early phases of the software construction process. The aim of this Ph.D. Thesis is to make signi cant contributions in search-based software engineering and, specially, in the area of software architecture optimisation. Although it is an area in which signi cant progress is being done, most of the current proposals are focused on generating low-level architectures or selecting and deploying already developed artefacts. Therefore, there is a lack of proposals dealing with architectural modelling at a high level of abstraction. At this level, engineers do not have a deep understanding of the system yet, meaning that assisting them is even more di cult. As case study, the discovery of component-based software architectures has been primary addressed. The objective for this problem consists in the abstraction of the architectural blocks, and their interactions, that best de ne the current structure of a software system. This can be viewed as the rst step an engineer would perform in order to further analyse and improve the system architecture. In this Ph.D. Thesis, the use of a great variety of search techniques has been explored. The suitability of these techniques has been studied, also making the necessary adaptations to cope with the aforementioned challenges. A rst proposal has been focused on the formulation of software architecture discovery as an optimisation problem, which consists in the computational representation of its software artefacts and the de nition of software metrics to evaluate their quality during the search process. Moreover, a single-objective evolutionary algorithm has been designed for its resolution, which has been validated using real software systems. The resulting model is comprehensible and exible, since its components have been designed under software engineering standards and tools and are also con gurable according to engineer's needs. Next, the discovery of software architectures has been tackled from a multi-objective perspective, in which several software metrics, often in con ict, have to be simultaneously optimised. In this case, the problem is solved by applying eight state-of-theart algorithms, including some recent many-objective approaches. These algorithms have been adapted to the problem and compared in an extensive experimental study, whose purpose is to analyse the in uence of the number and combination of metrics when guiding the search process. Apart from the performance validation following usual practices within the eld, this study provides a detailed analysis of the practical
implications behind the optimisation of multiple objectives in the context of
decision support.
The last proposal is focused on interactively including the engineer's opinion in the
search-based architecture discovery process. To do this, an interaction mechanism
has been designed, which allows the engineer to express desired characteristics for
the solutions (positive preferences), as well as those aspects that should be avoided
(negative preferences). The gathered information is combined with the software
metrics used until the moment, thus making possible to adapt the search as the
engineer interacts. Due to the characteristics of the proposed model, engineers of
di erent expertise in software development have participated in its validation with
the aim of showing the suitability and utility of the approach.
The knowledge acquired along the development of the Thesis, as well as the proposed
approaches, have also been transferred to other search-based software engineering
areas as a result of research collaborations. In this sense, it is worth noting the
formalisation of interactive search-based software engineering as a cross-cutting discipline,
which aims at promoting the active participation of the engineer during the
search process. Furthermore, the use of many-objective algorithms has been explored
in the context of service-oriented computing to address the so-called web service
composition problem
Metaheuristic Design Patterns: New Perspectives for Larger-Scale Search Architectures
Design patterns capture the essentials of recurring best practice in an abstract form. Their merits are well established in domains as diverse as architecture and software development. They offer significant benefits, not least a common conceptual vocabulary for designers, enabling greater communication of high-level concerns and increased software reuse. Inspired by the success of software design patterns, this chapter seeks to promote the merits of a pattern-based method to the development of metaheuristic search software components. To achieve this, a catalog of patterns is presented, organized into the families of structural, behavioral, methodological and component-based patterns. As an alternative to the increasing specialization associated with individual metaheuristic search components, the authors encourage computer scientists to embrace the ‘cross cutting' benefits of a pattern-based perspective to optimization algorithms. Some ways in which the patterns might form the basis of further larger-scale metaheuristic component design automation are also discussed
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An Evaluation of Performance Enhancements to Particle Swarm Optimisation on Real-World Data
Swarm Computation is a relatively new optimisation paradigm. The basic premise is to model the collective behaviour of self-organised natural phenomena such as swarms, flocks and shoals, in order to solve optimisation problems. Particle Swarm Optimisation (PSO) is a type of swarm computation inspired by bird flocks or swarms of bees by modelling their collective social influence as they search for optimal solutions.
In many real-world applications of PSO, the algorithm is used as a data pre-processor for a neural network or similar post processing system, and is often extensively modified to suit the application. The thesis introduces techniques that allow unmodified PSO to be applied successfully to a range of problems, specifically three extensions to the basic PSO algorithm: solving optimisation problems by training a hyperspatial matrix, using a hierarchy of swarms to coordinate optimisation on several data sets simultaneously, and dynamic neighbourhood selection in swarms.
Rather than working directly with candidate solutions to an optimisation problem, the PSO algorithm is adapted to train a matrix of weights, to produce a solution to the problem from the inputs. The search space is abstracted from the problem data.
A single PSO swarm optimises a single data set and has difficulties where the data set comprises disjoint parts (such as time series data for different days). To address this problem, we introduce a hierarchy of swarms, where each child swarm optimises one section of the data set whose gbest particle is a member of the swarm above in the hierarchy. The parent swarm(s) coordinate their children and encourage more exploration of the solution space. We show that hierarchical swarms of this type perform better than single swarm PSO optimisers on the disjoint data sets used.
PSO relies on interaction between particles within a neighbourhood to find good solutions. In many PSO variants, possible interactions are arbitrary and fixed on initialisation. Our third contribution is a dynamic neighbourhood selection: particles can modify their neighbourhood, based on the success of the candidate neighbour particle. As PSO is intended to reflect the social interaction of agents, this change significantly increases the ability of the swarm to find optimal solutions. Applied to real-world medical and cosmological data, this modification is and shows improvements over standard PSO approaches with fixed neighbourhoods
Numerical and Evolutionary Optimization 2020
This book was established after the 8th International Workshop on Numerical and Evolutionary Optimization (NEO), representing a collection of papers on the intersection of the two research areas covered at this workshop: numerical optimization and evolutionary search techniques. While focusing on the design of fast and reliable methods lying across these two paradigms, the resulting techniques are strongly applicable to a broad class of real-world problems, such as pattern recognition, routing, energy, lines of production, prediction, and modeling, among others. This volume is intended to serve as a useful reference for mathematicians, engineers, and computer scientists to explore current issues and solutions emerging from these mathematical and computational methods and their applications
Combining evolutionary algorithms and agent-based simulation for the development of urbanisation policies
Urban-planning authorities continually face the problem of optimising the allocation of green space over time in developing urban environments. To help in these decision-making processes, this thesis provides an empirical study of using evolutionary approaches to solve sequential decision making problems under uncertainty in stochastic environments. To achieve this goal, this work is underpinned by developing a theoretical framework based on the economic model of Alonso and the associated methodology for modelling spatial and temporal urban growth, in order to better understand the complexity inherent in this kind of system and to generate and improve relevant knowledge for the urban planning community. The model was hybridised with cellular automata and agent-based model and extended to encompass green space planning based on urban cost and satisfaction. Monte Carlo sampling techniques and the use of the urban model as a surrogate tool were the two main elements investigated and applied to overcome the noise and uncertainty derived from dealing with future trends and expectations. Once the evolutionary algorithms were equipped with these mechanisms, the problem under consideration was defined and characterised as a type of adaptive submodular. Afterwards, the performance of a non-adaptive evolutionary approach with a random search and a very smart greedy algorithm was compared and in which way the complexity that is linked with the configuration of the problem modifies the performance of both algorithms was analysed. Later on, the application of very distinct frameworks incorporating evolutionary algorithm approaches for this problem was explored: (i) an ‘offline’ approach, in which a candidate solution encodes a complete set of decisions, which is then evaluated by full simulation, and (ii) an ‘online’ approach which involves a sequential series of optimizations, each making only a single decision, and starting its simulations from the endpoint of the previous run
A Multiobjective Approach Applied to the Protein Structure Prediction Problem
Interest in discovering a methodology for solving the Protein Structure Prediction problem extends into many fields of study including biochemistry, medicine, biology, and numerous engineering and science disciplines. Experimental approaches, such as, x-ray crystallographic studies or solution Nuclear Magnetic Resonance Spectroscopy, to mathematical modeling, such as minimum energy models are used to solve this problem. Recently, Evolutionary Algorithm studies at the Air Force Institute of Technology include the following: Simple Genetic Algorithm (GA), messy GA, fast messy GA, and Linkage Learning GA, as approaches for potential protein energy minimization. Prepackaged software like GENOCOP, GENESIS, and mGA are in use to facilitate experimentation of these techniques. In addition to this software, a parallelized version of the fmGA, the so-called parallel fast messy GA, is found to be good at finding semi-optimal answers in reasonable wall clock time. The aim of this work is to apply a Multiobjective approach to solving this problem using a modified fast messy GA. By dividing the CHARMm energy model into separate objectives, it should be possible to find structural configurations of a protein that yield lower energy values and ultimately more correct conformations
Into the Unknown: How Computation Can Help Explore Uncharted Material Space
Novel functional materials are urgently needed to help combat the major global challenges facing humanity, such as climate change and resource scarcity. Yet, the traditional experimental materials discovery process is slow and the material space at our disposal is too vast to effectively explore using intuition-guided experimentation alone. Most experimental materials discovery programs necessarily focus on exploring the local space of known materials, so we are not fully exploiting the enormous potential material space, where more novel materials with unique properties may exist. Computation, facilitated by improvements in open-source software and databases, as well as computer hardware has the potential to significantly accelerate the rational development of materials, but all too often is only used to postrationalize experimental observations. Thus, the true predictive power of computation, where theory leads experimentation, is not fully utilized. Here, we discuss the challenges to successful implementation of computation-driven materials discovery workflows, and then focus on the progress of the field, with a particular emphasis on the challenges to reaching novel materials
Model based test suite minimization using metaheuristics
Software testing is one of the most widely used methods for quality assurance and fault detection purposes. However, it is one of the most expensive, tedious and time consuming activities in software development life cycle. Code-based and specification-based testing has been going on for almost four decades. Model-based testing (MBT) is a relatively new approach to software testing where the software models as opposed to other artifacts (i.e. source code) are used as primary source of test cases. Models are simplified representation of a software system and are cheaper to execute than the original or deployed system. The main objective of the research presented in this thesis is the development of a framework for improving the efficiency and effectiveness of test suites generated from UML models. It focuses on three activities: transformation of Activity Diagram (AD) model into Colored Petri Net (CPN) model, generation and evaluation of AD based test suite and optimization of AD based test suite. Unified Modeling Language (UML) is a de facto standard for software system analysis and design. UML models can be categorized into structural and behavioral models. AD is a behavioral type of UML model and since major revision in UML version 2.x it has a new Petri Nets like semantics. It has wide application scope including embedded, workflow and web-service systems. For this reason this thesis concentrates on AD models. Informal semantics of UML generally and AD specially is a major challenge in the development of UML based verification and validation tools. One solution to this challenge is transforming a UML model into an executable formal model. In the thesis, a three step transformation methodology is proposed for resolving ambiguities in an AD model and then transforming it into a CPN representation which is a well known formal language with extensive tool support. Test case generation is one of the most critical and labor intensive activities in testing processes. The flow oriented semantic of AD suits modeling both sequential and concurrent systems. The thesis presented a novel technique to generate test cases from AD using a stochastic algorithm. In order to determine if the generated test suite is adequate, two test suite adequacy analysis techniques based on structural coverage and mutation have been proposed. In terms of structural coverage, two separate coverage criteria are also proposed to evaluate the adequacy of the test suite from both perspectives, sequential and concurrent. Mutation analysis is a fault-based technique to determine if the test suite is adequate for detecting particular types of faults. Four categories of mutation operators are defined to seed specific faults into the mutant model. Another focus of thesis is to improve the test suite efficiency without compromising its effectiveness. One way of achieving this is identifying and removing the redundant test cases. It has been shown that the test suite minimization by removing redundant test cases is a combinatorial optimization problem. An evolutionary computation based test suite minimization technique is developed to address the test suite minimization problem and its performance is empirically compared with other well known heuristic algorithms. Additionally, statistical analysis is performed to characterize the fitness landscape of test suite minimization problems. The proposed test suite minimization solution is extended to include multi-objective minimization. As the redundancy is contextual, different criteria and their combination can significantly change the solution test suite. Therefore, the last part of the thesis describes an investigation into multi-objective test suite minimization and optimization algorithms. The proposed framework is demonstrated and evaluated using prototype tools and case study models. Empirical results have shown that the techniques developed within the framework are effective in model based test suite generation and optimizatio
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