The scalability of parallel applications executing on multithreaded and multicore multiprocessors is often quite limited due to large degrees of contention over shared resources on these systems. In fact, negative scalability frequently occurs such that a non-negligable performance loss is observed through the use of more processors and cores. In this dissertation, we present a prediction model for identifying efficient operating points of concurrency in multithreaded scientific applications in terms of both performance as a primary objective and power secondarily. We also present a runtime system that uses live analysis of hardware event rates through the prediction model to optimize applications dynamically. We discuss a dynamic, phase-aware performance prediction model (DPAPP), which combines statistical learning techniques, including multivariate linear regression and artificial neural networks, with runtime analysis of data collected from hardware event counters to locate optimal operating points of concurrency. We find that the scalability model achieves accuracy approaching 95%, sufficiently accurate to identify improved concurrency levels and thread placements from within real parallel scientific applications. Using DPAPP, we develop a prediction-driven runtime optimization scheme, called ACTOR, which throttles concurrency so that power consumption can be reduced and performance can be set at the knee of the scalability curve of each parallel execution phase in an application. ACTOR successfully identifies and exploits program phases where limited scalability results in a performance loss through the use of more processing elements, providing simultaneous reductions in execution time by 5%-18% and power consumption by 0%-11% across a variety of parallel applications and architectures. Further, we extend DPAPP and ACTOR to include support for runtime adaptation of DVFS, allowing for the synergistic exploitation of concurrency throttling and DVFS from within a single, autonomically-acting library, providing improved energy-efficiency compared to either approach in isolation. / Ph. D.

Power has become a primary concern for HPC systems. Dynamic voltage and frequency scaling (DVFS) and dynamic concurrency throttling (DCT) are two software tools (or knobs) for reducing the dynamic power consumption of HPC systems. To date, few works have considered the synergistic integration of DVFS and DCT in performance-constrained systems, and, to the best of our knowledge, no prior research has developed application-aware simultaneous DVFS and DCT controllers in real systems and parallel programming frameworks. We present a multi-dimensional, online performance prediction framework, which we deploy to address the problem of simultaneous runtime optimization of DVFS, DCT, and thread placement on multi-core systems. We present results from an implementation of the prediction framework in a runtime system linked to the Intel OpenMP runtime environment and running on a real dual-processor quad-core system as well as a dual-processor dual-core system. We show that the prediction framework derives near-optimal settings of the three power-aware program adaptation knobs that we consider. Our overall runtime optimization framework achieves significant reductions in energy (12.27% mean) and ED² (29.6% mean), through simultaneous power savings (3.9% mean) and performance improvements (10.3% mean). Our prediction and adaptation framework outperforms earlier solutions that adapt only DVFS or DCT, as well as one that sequentially applies DCT then DVFS. Further, our results indicate that prediction-based schemes for runtime adaptation compare favorably and typically improve upon heuristic search-based approaches in both performance and energy savings. / Master of Science

Green computing, an emerging field of research that seeks to reduce excess power consumption in high performance computing (HPC), is gaining popularity among researchers. Research in this field often relies on simulation or only uses a small cluster, typically 8 or 16 nodes, because of the lack of hardware support. In contrast, System G at Virginia Tech is a 2592 processor supercomputer equipped with power aware components suitable for large scale green computing research. DIRECT is a deterministic global optimization algorithm, implemented in the mathematical software package VTDIRECT95. This thesis explores the potential energy savings for the parallel implementation of DIRECT, called pVTdirect, when used with a large scale computational biology application, parameter estimation for a budding yeast cell cycle model, on System G. Two power aware approaches for pVTdirect are developed and compared against the CPUSPEED power saving system tool. The results show that knowledge of the parallel workload of the underlying application is beneficial for power management. / Master of Science

By 2004, microprocessor design focused on multicore scaling"increasing the number of cores per die in each generation "as the primary strategy for improving performance. These multicore processors typically equip multiple memory subsystems to improve data throughput. In addition, these systems employ heterogeneous processors such as GPUs and heterogeneous memories like non-volatile memory to improve performance, capacity, and energy efficiency. With the increasing volume of hardware resources and system complexity caused by heterogeneity, future systems will require intelligent ways to manage hardware resources. Early research to improve performance and energy efficiency on heterogeneous, multi-core, multi-memory systems focused on tuning a single primitive or at best a few primitives in the systems. The key limitation of past efforts is their lack of a holistic approach to resource management that balances the tradeoff between performance and energy consumption. In addition, the shift from simple, homogeneous systems to these heterogeneous, multicore, multi-memory systems requires in-depth understanding of efficient resource management for scalable execution, including new models that capture the interchange between performance and energy, smarter resource management strategies, and novel low-level performance/energy tuning primitives and runtime systems. Tuning an application to control available resources efficiently has become a daunting challenge; managing resources in automation is still a dark art since the tradeoffs among programming, energy, and performance remain insufficiently understood. In this dissertation, I have developed theories, models, and resource management techniques to enable energy-efficient execution of parallel applications through thread and data management in these heterogeneous multi-core, multi-memory systems. I study the effect of dynamic concurrent throttling on the performance and energy of multi-core, non-uniform memory access (NUMA) systems. I use critical path analysis to quantify memory contention in the NUMA memory system and determine thread mappings. In addition, I implement a runtime system that combines concurrent throttling and a novel thread mapping algorithm to manage thread resources and improve energy efficient execution in multi-core, NUMA systems. In addition, I propose an analytical model based on the queuing method that captures important factors in multi-core, multi-memory systems to quantify the tradeoff between performance and energy. The model considers the effect of these factors in a holistic fashion that provides a general view of performance and energy consumption in contemporary systems. Finally, I focus on resource management of future heterogeneous memory systems, which may combine two heterogeneous memories to scale out memory capacity while maintaining reasonable power use. I present a new memory controller design that combines the best aspects of two baseline heterogeneous page management policies to migrate data between two heterogeneous memories so as to optimize performance and energy. / Ph. D.

In this dissertation, we study multi-robot coordination in the context of multi-target tracking. Specifically, we are interested in the coordination achieved by means of submodular function optimization. Submodularity encodes the diminishing returns property that arises in multi-robot coordination. For example, the marginal gain of assigning an additional robot to track the same target diminishes as the number of robots assigned increases. The advantage of formulating coordination problems as submodular optimization is that a simple, greedy algorithm is guaranteed to give a good performance. However, often this comes at the expense of unrealistic models and assumptions. For example, the standard formulation does not take into account the fact that robots may fail, either randomly or due to adversarial attacks. When operating in uncertain conditions, we typically seek to optimize the expected performance. However, this does not give any flexibility for a user to seek conservative or aggressive behaviors from the team of robots. Furthermore, most coordination algorithms force robots to communicate at each time step, even though they may not need to. Our goal in this dissertation is to overcome these limitations by devising coordination algorithms that are parsimonious in communication, allow a user to manage the risk of the robot performance, and are resilient to worst-case robot failures and attacks. In the first part of this dissertation, we focus on designing parsimonious communication strategies for target tracking. Specifically, we investigate the problem of determining when to communicate and who to communicate with. When the robots use range sensors, the tracking performance is a function of the relative positions of the robots and the targets. We propose a self-triggered communication strategy in which a robot communicates its own position with its neighbors only when a certain set of conditions are violated. We prove that this strategy converges to the optimal robot positions for tracking a single target and in practice, reduces the number of communication messages by 30%. When tracking multiple targets, we can reduce the communication by forming subsets of robots and assigning one subset to track a target. We investigate a number of measures for tracking quality based on the observability matrix and show which ones are submodular and which ones are not. For non-submodular measures, we show a greedy algorithm gives a 1/(n+1) approximation, if we restrict the subset to n robots. In optimizing submodular functions, a common assumption is that the function value is deterministic, which may not hold in practice. For example, the sensor performance may depend on environmental conditions which are not known exactly. In the second part of the dissertation, we design an algorithm for stochastic submodular optimization. The standard formulation for stochastic optimization optimizes the expected performance. However, the expectation is a risk-neutral measure. Instead, we optimize the Conditional Value-at-Risk (CVaR), which allows the user the flexibility of choosing a risk level. We present an algorithm, based on the greedy algorithm, and prove that its performance has bounded suboptimality and improves with running time. We also present an online version of the algorithm to adapt to real-time scenarios. In the third part of this dissertation, we focus on scenarios where a set of robots may fail naturally or due to adversarial attacks. Our objective is to track as many targets as possible, a submodular measure, assuming worst-case robot failures. We present both centralized and distributed resilient tracking algorithms to cope with centralized and distributed communication settings. We prove these algorithms give a constant-factor approximation of the optimal in polynomial running time. / Doctor of Philosophy / Today, robotics and autonomous systems have been increasingly used in various areas such as manufacturing, military, agriculture, medical sciences, and environmental monitoring. However, most of these systems are fragile and vulnerable to adversarial attacks and uncertain environmental conditions. In most cases, even if a part of the system fails, the entire system performance can be significantly undermined. As robots start to coexist with humans, we need algorithms that can be trusted under real-world, not just ideal conditions. Thus, this dissertation focuses on enabling security, trustworthiness, and long-term autonomy in robotics and autonomous systems. In particular, we devise coordination algorithms that are resilient to attacks, trustworthy in the face of the uncertain conditions, and allow the long-term operation of multi-robot systems. We evaluate our algorithms through extensive simulations and proof-of-concept experiments. Generally speaking, multi-robot systems form the "physical" layer of Cyber-Physical Sytems (CPS), the Internet of Things (IoT), and Smart City. Thus, our research can find applications in the areas of connected and autonomous vehicles, intelligent transportation, communications and sensor networks, and environmental monitoring in smart cities.

Due to the limited computation and storage resources of Internet of Things (IoT) devices, many emerging intelligent applications based on deep learning techniques heavily depend on cloud computing for computation and storage. However, cloud computing faces technical issues with long latency, poor reliability, and weak privacy, resulting in the need for on-device computation and storage. Also, on-device computation is essential for many time-critical applications, which require real-time data processing and energy-efficient. Furthermore, the escalating requirements for on-device processing are driven by network bandwidth limitations and consumer anticipations concerning data privacy and user experience. In the realm of computing, there is a growing interest in exploring novel technologies that can facilitate ongoing advancements in performance. Of the various prospective avenues, the field of neuromorphic computing has garnered significant recognition as a crucial means to achieve fast and energy-efficient machine intelligence applications for IoT devices. The programming of neuromorphic computing hardware typically involves the construction of a spiking neural network (SNN) capable of being deployed onto the designated neuromorphic hardware. This dissertation presents a range of methodologies aimed at enhancing the precision and energy efficiency of SNNs. To be more precise, these advancements are achieved by incorporating four essential methods. The first method is the quantization of neural networks through knowledge distillation. This work introduces a quantization technique that effectively reduces the computational and storage resource requirements of a model while minimizing the loss of accuracy. To further enhance the reduction of quantization errors, the second method introduces a novel quantization-aware training algorithm specifically designed for training quantized spiking neural network (SNN) models intended for execution on the Loihi chip, a specialized neuromorphic computing chip. SNNs generally exhibit lower accuracy performance compared to deep neural networks (DNNs). The third approach introduces a DNN-SNN co-learning algorithm, which enhances the performance of SNN models by leveraging knowledge obtained from DNN models. The design of the neural architecture plays a vital role in enhancing the accuracy and energy efficiency of an SNN model. The fourth method presents a novel neural architecture search algorithm specifically tailored for SNNs on the Loihi chip. The method selects an optimal architecture based on gradients induced by the architecture at initialization across different data samples without the need for training the architecture. To demonstrate the effectiveness and performance across diverse machine intelligence applications, our methods are evaluated through (i) image classification, (ii) spectrum sensing, and (iii) modulation symbol detection. / Doctor of Philosophy / In the emerging Internet of Things (IoT), our everyday devices, from smart home gadgets to wearables, can autonomously make intelligent decisions. However, due to their limited computing power and storage, many IoT devices heavily depend on cloud computing, which brings along issues like slow response times, privacy concerns, and unreliable connections. Neuromorphic computing is a recognized and crucial approach for achieving fast and energy-efficient machine intelligence applications in IoT devices. Inspired by the human brain's neural networks, this cutting-edge approach allows devices to perform complex tasks efficiently and in real-time. The programming of this neuromorphic hardware involves creating spiking neural networks (SNNs). This dissertation presents several innovative methods to improve the precision and energy efficiency of these SNNs. Firstly, a technique called "quantization" reduces the computational and storage requirements of models without sacrificing accuracy. Secondly, a unique training algorithm is designed to enhance the performance of SNN models. Thirdly, a clever co-learning algorithm allows SNN models to learn from traditional deep neural networks (DNNs), further improving their accuracy. Lastly, a novel neural architecture search algorithm finds the best architecture for SNNs on the designated neuromorphic chip, without the need for extensive training. By making IoT devices smarter and more efficient, neuromorphic computing brings us closer to a world where our gadgets can perform intelligent tasks independently, enhancing convenience and privacy for users across the globe.

En este estudio analizamos las analogías estéticas y filosóficas entre los tres términos orientales principales del medievo japonés: mono no aware, wabi sabi y y¿gen y el `arte de la tierra¿ surgido en Europa en la década de los setenta llamado también Land Art. Cabe destacar, que hemos optado por incluir en este estudio únicamente la vertiente europea de Land Art, más que por la necesidad de acotar una investigación de esta índole, por las discrepancias que surgen entre los Earthworks norteamericanos y el arte medieval oriental. Las concomitancias encontradas entre el `arte de la tierra¿ y el arte medieval japonés constituyen el resultado de una búsqueda, emprendida por occidente, que va más allá del ámbito puramente artístico, ya que responde a cuestiones filosóficas, sociales y culturales sobre nuevos modos de experimentar la existencia. Podemos encontrar los primeros signos de dichas influencias extremoorientales en la ruptura con la concepción clásica del arte; es decir, en el romanticismo. El arte romántico, con su nueva visión de la naturaleza, supuso la revalorización del paisaje como autentico protagonista de una obra. Los artistas Land Art, rescatando la categoría de lo sublime en el arte, proponen una nueva relación entre el hombre y la naturaleza, basada en el respeto y comprensión de la misma, muy próxima a axiomas orientales. No en vano, ha sido en las obras iniciales de Land Art europeas donde críticos contemporáneos han encontrado mayores similitudes con la estetica medieval japonesa. Dos han sido los artistas 'viajeros' alrededor de los cuales han proliferado las comparaciones con el arte zen: Richard Long y Hamish Fulton. En el caso de éste último, autores como Robert C. Morgan han hecho alusiones explícitas a la relación existente entre el zen y la cosmovisión del artista, las encontramos en el artículo `Hamish Fulton: El residuo de la vision / La apertura de la mente¿, dentro del libro ¿Del arte a la idea : Ensayos sobre arte conceptual¿ editado por Akal en el año 2003. También el propio artista ha hecho declaraciones sobre la influencia del arte zen en su obra, podemos verlo en: ¿Higurashi: Spiritual consequences of walking on the land¿, Kitakyushu: Center for Contemporary Art, 1999. En cuanto a Richard Long, la proximidad de su obra al arte del medievo japonés es un tema recurrente en los escritos de Anne Seymour, entre los cuales destacamos el prólogo al catálogo ¿Piedras¿ de Richard Long: 'El estanque de Bash¿ - una nueva perspectiva', editado por la dirección general de bellas artes y archivos del Ministerio de cultura, en 1986, así como también en los de Gloria Moure, muy especialmente en su prólogo al catálogo Spanish Stones, editado por la Diputación de Huesca en 1998. Nuestra tesis queda dividida del modo siguiente: En la primera parte definimos los términos a comparar, es decir, mono no aware, wabi sabi y y¿gen, analizando sus principales manifestaciones artísticas(ámbito literario, teatro n¿, haiku y haiga, Ceremonia del Té, jardines karesansui y pintura de tinta); Así como el Land Art europeo de la década de los setenta, centrándonos en la obra de Richard Long y Hamish Fulton. En la segunda parte compararemos el Land Art europeo con el arte japonés medieval, haciendo hincapié en los cuatro apartados donde, a nuestro entender, se dan el mayor número de concomitancias, estos son: `la naturaleza como materia del arte¿, `la belleza pintoresca de la sencillez¿, `hacia un arte de la experiencia¿ y `en los márgenes del arte¿. Esta comparativa general nos sirve de marco para adentrarnos en el análisis de los rasgos de estética medieval japonesa en la obra de Long y Fulton. Dichos rasgos son variados y dispares pero pueden resumirse en los siguientes aspectos: Existen actitudes zen en la actitud y en el quehacer artístico de nuestros artistas caminantes; Su planteamiento del paseo responde a una concepción poética del tiempo muy similar a la de los poetas errantes japoneses de antaño; La naturaleza es, tanto para uno como para otros, una especie de religión, su fuente de inspiración y el marco idóneo para realizar sus obras; Los escritos y las instalaciones que nuestros artistas producen en el camino, están marcadas por una estética austera y minimalista muy acorde con las expresiones artísticas propias del medievo japonés, como el suibokuga o los haikus; Y por último, la crítica que encierra la obra de todos ellos, tanto occidentales como orientales, ha sido erróneamente tachada de escapista. Más que una huida se trata de un encuentro. Un encuentro con el espíritu del paisaje, con la esencia poética del mismo. Teniendo en cuenta la crisis actual y la enorme cantidad de noticias negativas por parte de los medios a las que estamos expuestos, la obra de Richard Long y Hamish Fulton es como un bálsamo que nos recuerda que formamos parte de la naturaleza y que nuestra existencia sería más plena si se basara en un profundo respeto hacia ella. / Andrés Alzola, S. (2013). Signos de Wabi Sabi, Mono no Aware y Yügen en el Land Art europeo de la década de los setenta. Los paseos de Hamish Fulton y Richard Long como ejemplo paradigmático [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31647

[EN] The increasing adoption of process-aware information systems (PAISs) together with the high variability in business processes has resulted in collections of process families. These families correspond to a business process model and its variants, which can comprise hundreds or thousands of different ways of realizing this process. Modeling and managing process variability in this context can be very challenging due to the size of these families. Motivated by this challenge, several approaches enabling process variability have been developed. However, with these approaches PAIS engineers usually are required to model and manage one by one all the elements of a process family and ensure its correctness by their own. This can be tedious and error-prone especially when a process family comprises hundreds or thousands of process variants. For example, variability may not be properly reflected since PAIS engineers need to be aware of each variation of each process variant. Thus, there is a need of methods that allow PAIS engineers to model process variability more explicitly, especially at a level of abstraction higher than the one provided by the existing process variability approaches. However, how process variability is represented in existing approaches becomes critical for these methods (e.g., what language constructs are used to model process variability). In this context, the use of modeling patterns (reusable solutions to a commonly occurring problem) is a promising way to address these issues. For example, patterns have been proved as an efficient solution to model individual business processes. The objective of this thesis is to enhance the modeling of variability in process families through change patterns. First, we conduct a systematic study to analyze existing process variability approaches regarding their expressiveness with respect to process variability modeling as well as their process support. Thus, we can identify how process variability is actually modeled by existing approaches (i.e., a core set of variability-specific language constructs). In addition, based on the obtained empirical evidence, we derive the VIVACE framework, a complete characterization of process variability which comprises also a core set of features fostering process variability. VIVACE enables PAIS engineers to evaluate existing process variability approaches as well as to select that variability approach meeting their requirements best. In addition, it helps process engineers in dealing with PAISs supporting process variability. Second, to facilitate variability modeling in process families, based on the identified language constructs, we present a set of 10 change patterns and show how they can be implemented in a process variability approach. In particular, these patterns support process family modeling and evolution and are able to ensure process family correctness. In order to prove their effectiveness and analyze their suitability, we applied these change patterns in a real scenario. More concretely, we conduct a case study with a safety standard with a high degree of variability. The case study results show that the application of the change patterns can reduce the effort for process family modeling in a 34% and for evolution in a 40%. In addition, we have analyzed how PAIS engineers apply the patterns and their perceptions of this application. Most of them expressed some benefit when applying the change patterns, did not perceived an increase of mental effort for applying the patterns, and agreed upon the usefulness and ease of use of the patterns. / [ES] La creciente adopción de sistemas de información dirigidos por procesos de negocio (PAIS) junto con la alta variabilidad en dichos procesos, han dado lugar a la aparición de colecciones de familias de procesos. Estas familias están constituidas por un modelo de proceso de negocio y sus variantes, las cuales pueden comprender entre cientos y miles de diferentes formas de llevar a cabo ese proceso. Gestionar la variabilidad en este contexto puede resultar muy difícil dado el tamaño que estas familias pueden alcanzar. Motivados por este desafío, se han desarrollado varias soluciones que permiten la gestión de la variabilidad en los procesos de negocio. Sin embargo, con estas soluciones los ingenieros deben crear y gestionar uno por uno todos los elementos de las familias de procesos y asegurar ellos mismos su corrección. Esto puede resultar tedioso y propenso a errores especialmente cuando las familias están compuestas de miles de variantes. Por ejemplo, la variabilidad puede no quedar adecuadamente representada ya que los ingenieros deben ser conscientes de todas y cada una de las variaciones de todas las variantes. Así, son necesarios nuevos métodos que permitan modelar la variabilidad de los procesos de una manera más explícita, a un nivel de abstracción más alto del proporcionado por las soluciones actuales. Sin embargo, cómo se representa la variabilidad en estos métodos resulta crítico (ej.: qué primitivas se utilizan). En este contexto, el uso de patrones de modelado (soluciones reutilizables a un problema recurrente) resultan un camino prometedor. Por ejemplo, los patrones han sido probados como una solución eficaz para gestionar procesos de negocio individuales. El objetivo de esta tesis es mejorar el modelado de la variabilidad en las familias de procesos a través del uso de patrones de cambio. En primer lugar, hemos llevado a cabo un estudio sistemático con el fin de analizar las soluciones existentes que permiten gestionar la variabilidad en los procesos, así como el soporte que estas proporcionan. Así, hemos sido capaces de identificar y analizar cuál es el conjunto básico de primitivas específicas para representar la variabilidad. Además, basándonos en la evidencia empírica obtenida, hemos derivado el marco de evaluación VIVACE, el cual recoge las primitivas de variabilidad y un conjunto básico de características que favorecen la variabilidad en los procesos. El principal objetivo de VIVACE es conformar una completa caracterización de la variabilidad en los procesos de negocio. Asimismo, VIVACE permite evaluar las soluciones que gestionan la variabilidad en los procesos, así como seleccionar la solución que se ajuste mejor a sus necesidades. Finalmente, VIVACE puede ayudar a los ingenieros a gestionar PAISs con variabilidad. En segundo lugar, para facilitar el modelado de la variabilidad en las familias de procesos, basándonos en las primitivas identificadas, hemos definido un conjunto de 10 patrones de cambio y hemos mostrado cómo estos patrones pueden ser implementados. En particular, estos patrones ayudan al modelado y la evolución de familias de procesos y son capaces de garantizar la corrección de la propia familia. Para probar su efectividad y analizar su idoneidad, hemos aplicado estos patrones de cambio en un escenario real. En concreto, hemos llevado a cabo un caso de estudio con un estándar de seguridad con un alto nivel de variabilidad. Los resultados de este caso demuestran que la aplicación de nuestros patrones de cambio puede reducir el esfuerzo para el modelado de familias de procesos en un 34% y para la evolución de esos modelos en un 40%. Además, hemos analizado cómo los ingenieros aplican los patrones y cuáles son sus percepciones de esta aplicación. Como resultado, la mayoría de ellos encontró beneficios al aplicar los patrones. Además, no percibieron un aumento en el esfuerzo mental necesario para aplicarlos y estuvieron de acuerdo en la utilid / [CA] La creixent adopció de sistemes d'informació dirigits per processos de negoci (PAIS) junt amb l'alta variabilitat en eixos processos, han donat lloc a la aparició de col·leccions de famílies de processos. Estes famílies es formen de un model de procés de negoci i les seues variants, les quals poden comprendre entre cents i milers de diferents formes de dur a terme eixe procés. Modelar la variabilitat dels processos en este context pot resultar molt difícil donat la grandària que aquestes famílies poden aconseguir. Motivats per este desafiament, s'han desenvolupat diverses solucions que permeten la gestió de la variabilitat en els processos de negoci. No obstant, amb aquestes solucions els enginyers que treballen amb PAIS han de crear i gestionar un a un tots els elements de les famílies de processos i assegurar ells mateixos la seua correcció. Això pot resultar tediós i propens a errors especialment quan les famílies es componen de cents o milers de variants. Per exemple, la variabilitat pot no quedar adequadament representada ja que els enginyers han de ser conscients de totes i cadascuna una de les variacions de totes les variants. Per quest motiu, son necessaris nous mètodes que permeten als enginyers de PAIS modelar la variabilitat dels processos de manera més explícita, sobretot a un nivell d'abstracció més alt del proporcionat per les solucions actuals. No obstant, com es representa la variabilitat en aquestos mètodes resulta crític (ex.: quines primitives s'utilitzen per a modelar la variabilitat en els processos). En aquest context, l'ús de patrons de modelatge (solucions reutilitzables a un problema recurrent) resulten un camí prometedor. Per exemple, els patrons han sigut provats com una solució eficaç per modelar i gestionar processos de negoci individuals. L'objectiu d'aquesta tesi 'es millorar el modelatge de la variabilitat en les famílies de processos a través de l'ús de patrons de canvi. En primer lloc, hem dut a terme un estudi sistemàtic per a analitzar les solucions existents per a gestionar la variabilitat en els processos, així com el suport que aquestes proporcionen. D'aquesta manera, som capaços d'identificar i analitzar quin 'es el conjunt bàsic de primitives específiques per a representar la variabilitat. A més, basant-nos en l'evidència empírica obtinguda, hem derivat el marc d'evacuació VIVACE, el qual arreplega les primitives de variabilitat i un conjunt bàsic de característiques que afavoreixen la variabilitat en els processos. Així mateix, VIVACE permet als enginyers de PAIS avaluar les solucions per a gestionar la variabilitat en els processos, així com seleccionar la solució que s'ajusta millor a les seues necessitats. Finalment, VIVACE també pot ajudar als enginyers a gestionar PAISs que donen suport a aquesta variabilitat. En segon lloc, per a facilitar el modelatge de la variabilitat en les famílies de processos, basant-nos en les primitives identificades, hem definit un conjunt de 10 patrons de canvi i hem mostrat com aquestos poden ser implementats. En particular, estos patrons ajuden al modelatge i l'evolució de famílies de processos i garanteixen la correcció de la pròpia família. Per a provar la seua efectivitat i analitzar la seua idoneïtat, hem aplicat els patrons de canvi en un escenari real. En particular, hem dut a terme un cas d'estudi amb un estàndard de seguretat amb un alt nivell de variabilitat. Els resultats de aquest cas demostren que l'aplicació dels nostres patrons de canvi poden reduir l'esforç per al modelatge de famílies de processos en un 34% i per a l'evolució de eixos models en un 40%. A més, hem analitzat com els enginyers de PAIS apliquen els patrons i quines son les seues percepcions d'esta aplicació. Com a resultat, la majoria d'ells va trobar beneficis al aplicar els patrons de canvi. A més, no van percebre un augment en l'esforç mental necessari per a aplicar-los i van estar d'acord en la utilitat i f / Ayora Esteras, C. (2015). Enhancing Variability Modeling in Process-Aware Information Systems through Change Patterns [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58426

Tesis por compendio / [EN] Multi-Agent Systems (MAS), Argumentation and Automated Planning are three lines of investigations within the field of Artificial Intelligence (AI) that have been extensively studied over the last years. A MAS is a system composed of multiple intelligent agents that interact with each other and it is used to solve problems whose solution requires the presence of various functional and autonomous entities. Multi-agent systems can be used to solve problems that are difficult or impossible to resolve for an individual agent. On the other hand, Argumentation refers to the construction and subsequent exchange (iteratively) of arguments between a group of agents, with the aim of arguing for or against a particular proposal. Regarding Automated Planning, given an initial state of the world, a goal to achieve, and a set of possible actions, the goal is to build programs that can automatically calculate a plan to reach the final state from the initial state. The main objective of this thesis is to propose a model that combines and integrates these three research lines. More specifically, we consider a MAS as a team of agents with planning and argumentation capabilities. In that sense, given a planning problem with a set of objectives, (cooperative) agents jointly construct a plan to satisfy the objectives of the problem while they defeasibly reason about the environmental conditions so as to provide a stronger guarantee of success of the plan at execution time. Therefore, the goal is to use the planning knowledge to build a plan while agents beliefs about the impact of unexpected environmental conditions is used to select the plan which is less likely to fail at execution time. Thus, the system is intended to return collaborative plans that are more robust and adapted to the circumstances of the execution environment. In this thesis, we designed, built and evaluated a model of argumentation based on defeasible reasoning for planning cooperative multi-agent system. The designed system is independent of the domain, thus demonstrating the ability to solve problems in different application contexts. Specifically, the system has been tested in context sensitive domains such as Ambient Intelligence as well as with problems used in the International Planning Competitions. / [ES] Dentro de la Inteligencia Artificial (IA), existen tres ramas que han sido ampliamente estudiadas en los últimos años: Sistemas Multi-Agente (SMA), Argumentación y Planificación Automática. Un SMA es un sistema compuesto por múltiples agentes inteligentes que interactúan entre sí y se utilizan para resolver problemas cuya solución requiere la presencia de diversas entidades funcionales y autónomas. Los sistemas multiagente pueden ser utilizados para resolver problemas que son difíciles o imposibles de resolver para un agente individual. Por otra parte, la Argumentación consiste en la construcción y posterior intercambio (iterativamente) de argumentos entre un conjunto de agentes, con el objetivo de razonar a favor o en contra de una determinada propuesta. Con respecto a la Planificación Automática, dado un estado inicial del mundo, un objetivo a alcanzar, y un conjunto de acciones posibles, el objetivo es construir programas capaces de calcular de forma automática un plan que permita alcanzar el estado final a partir del estado inicial. El principal objetivo de esta tesis es proponer un modelo que combine e integre las tres líneas anteriores. Más específicamente, nosotros consideramos un SMA como un equipo de agentes con capacidades de planificación y argumentación. En ese sentido, dado un problema de planificación con un conjunto de objetivos, los agentes (cooperativos) construyen conjuntamente un plan para resolver los objetivos del problema y, al mismo tiempo, razonan sobre la viabilidad de los planes, utilizando como herramienta de diálogo la Argumentación. Por tanto, el objetivo no es sólo obtener automáticamente un plan solución generado de forma colaborativa entre los agentes, sino también utilizar las creencias de los agentes sobre la información del contexto para razonar acerca de la viabilidad de los planes en su futura etapa de ejecución. De esta forma, se pretende que el sistema sea capaz de devolver planes colaborativos más robustos y adaptados a las circunstancias del entorno de ejecución. En esta tesis se diseña, construye y evalúa un modelo de argumentación basado en razonamiento defeasible para un sistema de planificación cooperativa multiagente. El sistema diseñado es independiente del dominio, demostrando así la capacidad de resolver problemas en diferentes contextos de aplicación. Concretamente el sistema se ha evaluado en dominios sensibles al contexto como es la Inteligencia Ambiental y en problemas de las competiciones internacionales de planificación. / [CA] Dins de la intel·ligència artificial (IA), hi han tres branques que han sigut àmpliament estudiades en els últims anys: Sistemes Multi-Agent (SMA), Argumentació i Planificació Automàtica. Un SMA es un sistema compost per múltiples agents intel·ligents que interactúen entre si i s'utilitzen per a resoldre problemas la solución dels quals requereix la presència de diverses entitats funcionals i autònomes. Els sistemes multiagente poden ser utilitzats per a resoldre problemes que són difícils o impossibles de resoldre per a un agent individual. D'altra banda, l'Argumentació consistiex en la construcció i posterior intercanvi (iterativament) d'arguments entre un conjunt d'agents, amb l'objectiu de raonar a favor o en contra d'una determinada proposta. Respecte a la Planificació Automàtica, donat un estat inicial del món, un objectiu a aconseguir, i un conjunt d'accions possibles, l'objectiu és construir programes capaços de calcular de forma automàtica un pla que permeta aconseguir l'estat final a partir de l'estat inicial. El principal objectiu d'aquesta tesi és proposar un model que combine i integre les tres línies anteriors. Més específicament, nosaltres considerem un SMA com un equip d'agents amb capacitats de planificació i argumentació. En aquest sentit, donat un problema de planificació amb un conjunt d'objectius, els agents (cooperatius) construeixen conjuntament un pla per a resoldre els objectius del problema i, al mateix temps, raonen sobre la viabilitat dels plans, utilitzant com a ferramenta de diàleg l'Argumentació. Per tant, l'objectiu no és només obtindre automàticament un pla solució generat de forma col·laborativa entre els agents, sinó també utilitzar les creences dels agents sobre la informació del context per a raonar sobre la viabilitat dels plans en la seua futura etapa d'execució. D'aquesta manera, es pretén que el sistema siga capaç de tornar plans col·laboratius més robustos i adaptats a les circumstàncies de l'entorn d'execució. En aquesta tesi es dissenya, construeix i avalua un model d'argumentació basat en raonament defeasible per a un sistema de planificació cooperativa multiagent. El sistema dissenyat és independent del domini, demostrant així la capacitat de resoldre problemes en diferents contextos d'aplicació. Concretament el sistema s'ha avaluat en dominis sensibles al context com és la inte·ligència Ambiental i en problemes de les competicions internacionals de planificació. / Pajares Ferrando, S. (2016). Defeasible Argumentation for Cooperative Multi-Agent Planning [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/60159 / Compendio

Deep learning methods have achieved state-of-the-art performance in various tasks of medical image analysis. However, the success relies heavily on the expensive and time-consuming collection of large quantities of labeled data, which is not always available. This dissertation investigates the use of self-supervised and generative methods to enhance the label efficiency of deep learning models for 3D medical image analysis. Unlike natural images, medical images contain consistent anatomical contexts specific to the domain, which can be exploited as self-supervision signals to pre-train the model. Furthermore, generative methods can be utilized to synthesize additional samples, thereby increasing sample diversity. In the first part of the dissertation, we introduce self-supervised learning frameworks that learn anatomy-aware and disease-related representation. In order to learn disease-related representation, we propose two domain-specific contrasting strategies that leverage anatomical similarity across patients to create hard negative samples that incentivize learning fine-grained pathological features. In order to learn anatomy-sensitive representation, we develop a novel 3D convolutional layer with kernels that are conditionally parameterized based on the anatomical locations. We perform extensive experiments on large-scale datasets of CT scans, which show that our method improves the performance of many downstream tasks. In the second part of the dissertation, we introduce generative models capable of synthesizing high-resolution, anatomy-guided 3D medical images. Current generative models are typically limited to low-resolution outputs due to memory constraints, despite clinicians' need for high-resolution details in diagnoses. To overcome this, we present a hierarchical architecture that efficiently manages memory demands, enabling the generation of high-resolution images. In addition, diffusion-based generative models are becoming more prevalent in medical imaging. However, existing state-of-the-art methods often under-utilize the extensive information found in radiology reports and anatomical structures. To address these limitations, we propose a text-guided 3D image diffusion model that preserves anatomical details. We conduct experiments on downstream tasks and blind evaluation by radiologists, which demonstrate the clinical value of our proposed methodologies.