Multi-objective optimization in graphical models

Many real-life optimization problems are combinatorial, i.e. they concern a choice of the best solution from a finite but exponentially large set of alternatives. Besides, the solution quality of many of these problems can often be evaluated from several points of view (a.k.a. criteria). In that case, each criterion may be described by a different objective function. Some important and well-known multicriteria scenarios are: · In investment optimization one wants to minimize risk and maximize benefits. · In travel scheduling one wants to minimize time and cost. · In circuit design one wants to minimize circuit area, energy consumption and maximize speed. · In knapsack problems one wants to minimize load weight and/or volume and maximize its economical value. The previous examples illustrate that, in many cases, these multiple criteria are incommensurate (i.e., it is difficult or impossible to combine them into a single criterion) and conflicting (i.e., solutions that are good with respect one criterion are likely to be bad with respect to another). Taking into account simultaneously the different criteria is not trivial and several notions of optimality have been proposed. Independently of the chosen notion of optimality, computing optimal solutions represents an important current research challenge. Graphical models are a knowledge representation tool widely used in the Artificial Intelligence field. They seem to be specially suitable for combinatorial problems. Roughly, graphical models are graphs in which nodes represent variables and the (lack of) arcs represent conditional independence assumptions. In addition to the graph structure, it is necessary to specify its micro-structure which tells how particular combinations of instantiations of interdependent variables interact. The graphical model framework provides a unifying way to model a broad spectrum of systems and a collection of general algorithms to efficiently solve them. In this Thesis we integrate multi-objective optimization problems into the graphical model paradigm and study how algorithmic techniques developed in the graphical model context can be extended to multi-objective optimization problems. As we show, multiobjective optimization problems can be formalized as a particular case of graphical models using the semiring-based framework. It is, to the best of our knowledge, the first time that graphical models in general, and semiring-based problems in particular are used to model an optimization problem in which the objective function is partially ordered. Moreover, we show that most of the solving techniques for mono-objective optimization problems can be naturally extended to the multi-objective context. The result of our work is the mathematical formalization of multi-objective optimization problems and the development of a set of multiobjective solving algorithms that have been proved to be efficient in a number of benchmarks.Muchos problemas reales de optimización son combinatorios, es decir, requieren de la elección de la mejor solución (o solución óptima) dentro de un conjunto finito pero exponencialmente grande de alternativas. Además, la mejor solución de muchos de estos problemas es, a menudo, evaluada desde varios puntos de vista (también llamados criterios). Es este caso, cada criterio puede ser descrito por una función objetivo. Algunos escenarios multi-objetivo importantes y bien conocidos son los siguientes: · En optimización de inversiones se pretende minimizar los riesgos y maximizar los beneficios. · En la programación de viajes se quiere reducir el tiempo de viaje y los costes. · En el diseño de circuitos se quiere reducir al mínimo la zona ocupada del circuito, el consumo de energía y maximizar la velocidad. · En los problemas de la mochila se quiere minimizar el peso de la carga y/o el volumen y maximizar su valor económico. Los ejemplos anteriores muestran que, en muchos casos, estos criterios son inconmensurables (es decir, es difícil o imposible combinar todos ellos en un único criterio) y están en conflicto (es decir, soluciones que son buenas con respecto a un criterio es probable que sean malas con respecto a otra). Tener en cuenta de forma simultánea todos estos criterios no es trivial y para ello se han propuesto diferentes nociones de optimalidad. Independientemente del concepto de optimalidad elegido, el cómputo de soluciones óptimas representa un importante desafío para la investigación actual. Los modelos gráficos son una herramienta para la represetanción del conocimiento ampliamente utilizados en el campo de la Inteligencia Artificial que parecen especialmente indicados en problemas combinatorios. A grandes rasgos, los modelos gráficos son grafos en los que los nodos representan variables y la (falta de) arcos representa la interdepencia entre variables. Además de la estructura gráfica, es necesario especificar su (micro-estructura) que indica cómo interactúan instanciaciones concretas de variables interdependientes. Los modelos gráficos proporcionan un marco capaz de unificar el modelado de un espectro amplio de sistemas y un conjunto de algoritmos generales capaces de resolverlos eficientemente. En esta tesis integramos problemas de optimización multi-objetivo en el contexto de los modelos gráficos y estudiamos cómo diversas técnicas algorítmicas desarrolladas dentro del marco de los modelos gráficos se pueden extender a problemas de optimización multi-objetivo. Como mostramos, este tipo de problemas se pueden formalizar como un caso particular de modelo gráfico usando el paradigma basado en semi-anillos (SCSP). Desde nuestro conocimiento, ésta es la primera vez que los modelos gráficos en general, y el paradigma basado en semi-anillos en particular, se usan para modelar un problema de optimización cuya función objetivo está parcialmente ordenada. Además, mostramos que la mayoría de técnicas para resolver problemas monoobjetivo se pueden extender de forma natural al contexto multi-objetivo. El resultado de nuestro trabajo es la formalización matemática de problemas de optimización multi-objetivo y el desarrollo de un conjunto de algoritmos capaces de resolver este tipo de problemas. Además, demostramos que estos algoritmos son eficientes en un conjunto determinado de benchmarks

Seeking the Self in Pigment and Pixels: Postmodernism, Art, and the Subject

In this study, I examine how works of art become vehicles for the postmodern inquiry into the nature of subjectivity. My thesis narrows the focus to those characters who attempt to ground themselves in works of art, especially representational paintings. I argue that, to cope with what they see as the chaos of a decentered postmodern world, these figures try to anchor their confused identities in what they wrongfully interpret as stable and mimetic artworks. Nostalgic for an imagined past when representation was transparent and corresponded to reality, they believe that traditional figurative art offers the promise of cohesive meaning otherwise lacking under postmodernism. Their views of art, therefore, underwrite a desire and nostalgia for absolutes that are non-existent. In their failure to ground themselves in images, we see the fundamental instability of both the subject and of art. The wayward individuals that I examine yearn for art objects to come to life in order to confirm their own selfhood. What they seek, then, is to transform art-objects into art-subjects; this Pygmalionesque project is grounded in the futile hope that the art-object can reciprocate their desires. We find literary examples of this trend in the characters I analyze in my first two chapters: notably the narrator(s) of John Banville’s Frames Trilogy and the gay spies of the fictionalized Cambridge Five. In my final chapter, I look to the clones and androids of popular culture and explore the real life example of Japanese love-doll owners. In each of these instances, artworks are strategically positioned as sites of ontological anchorage, but this foundation can never be secure under postmodernism. Despite their fervent hopes, these characters have misplaced their trust in a form of representation that is no more stable than any other aspect of the postmodern condition. I argue that Freddie, Victor, Tommy, and Tavo, among others, are particularly good examples of the vexed relationship between the image and the self

On Maximum Weight Clique Algorithms, and How They Are Evaluated

Maximum weight clique and maximum weight independent set solvers are often benchmarked using maximum clique problem instances, with weights allocated to vertices by taking the vertex number mod 200 plus 1. For constraint programming approaches, this rule has clear implications, favouring weight-based rather than degree-based heuristics. We show that similar implications hold for dedicated algorithms, and that additionally, weight distributions affect whether certain inference rules are cost-effective. We look at other families of benchmark instances for the maximum weight clique problem, coming from winner determination problems, graph colouring, and error-correcting codes, and introduce two new families of instances, based upon kidney exchange and the Research Excellence Framework. In each case the weights carry much more interesting structure, and do not in any way resemble the 200 rule. We make these instances available in the hopes of improving the quality of future experiments

Interlitteraria : Tartu Ülikooli maailmakirjanduse õppetooli ja Eesti Võrdleva Kirjandusteaduse Assotsiatsiooni rahvusvaheline ajakiri = international refereed edition of the Chair of Comparative Literature of Tartu University and the Estonian Association of Comparative Literature

http://www.ester.ee/record=b1226153*es

Constraint solving over multi-valued logics - application to digital circuits

Due to usage conditions, hazardous environments or intentional causes, physical and virtual systems are subject to faults in their components, which may affect their overall behaviour. In a ‘black-box’ agent modelled by a set of propositional logic rules, in which just a subset of components is externally visible, such faults may only be recognised by examining some output function of the agent. A (fault-free) model of the agent’s system provides the expected output given some input. If the real output differs from that predicted output, then the system is faulty. However, some faults may only become apparent in the system output when appropriate inputs are given. A number of problems regarding both testing and diagnosis thus arise, such as testing a fault, testing the whole system, finding possible faults and differentiating them to locate the correct one. The corresponding optimisation problems of finding solutions that require minimum resources are also very relevant in industry, as is minimal diagnosis. In this dissertation we use a well established set of benchmark circuits to address such diagnostic related problems and propose and develop models with different logics that we formalise and generalise as much as possible. We also prove that all techniques generalise to agents and to multiple faults. The developed multi-valued logics extend the usual Boolean logic (suitable for faultfree models) by encoding values with some dependency (usually on faults). Such logics thus allow modelling an arbitrary number of diagnostic theories. Each problem is subsequently solved with CLP solvers that we implement and discuss, together with a new efficient search technique that we present. We compare our results with other approaches such as SAT (that require substantial duplication of circuits), showing the effectiveness of constraints over multi-valued logics, and also the adequacy of a general set constraint solver (with special inferences over set functions such as cardinality) on other problems. In addition, for an optimisation problem, we integrate local search with a constructive approach (branch-and-bound) using a variety of logics to improve an existing efficient tool based on SAT and ILP

Transforming the Law of One: Anne Sexton and Sylvia Plath from a Kristevan perspective

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A recent trend in the study of Anne Sexton and Sylvia Plath often dissociates Confessional poetry from the subject of the writer and her biography, claiming that the artist is in full control of her work and that her art does not have naïve mimetic qualities. However, this study proposes that subjective attributes, namely negativity and abjection, enable a powerful transformative dialectic. Specifically, it demonstrates that an emphasis on the subjective can help manifest the process of transgressing the law of One. The law of One asserts a patriarchal, monotheistic law as a social closed system and can be opposed to the bodily drives and its open dynamism. This project asserts that unique, creative voices are derived from that which is individual and personal and thus, readings of Confessional poetry are in fact best served by acknowledgment of the subjective. In order to stress the subject of the artist in Confessionalism, this study employed a psychoanalytical Kristevan approach. This enables consideration of the subject not only in terms of the straightforward narration of her life, but also in relation to her poetic language and the process of creativity where instinctual drives are at work. This study further applies a feminist reading to the subject’s poetic language and its ability to transgress the law, not necessarily in the political, macrocosmic sense of the word, but rather on the microcosmic, subjective level. Although Sexton and Plath possess similar biographies, their work does not have the same artistic value in terms of transformative capabilities. Transformation here signifies transgressing of the unity of the subject and of the authoritative father, the other within, who has prohibitive social and linguistic powers. Plath, Kristeva’s the “deadmost,” successfully confronts the unity of the law, releasing the death drive through anger. Moreover, Plath’s psychic borders are more fluid because of her ability to identify with the pre-Oedipal mother. This unsettling subject is identified by shifts in texts marked by renewal, transgression, and jouissance. Unlike Sexton, Plath is able to achieve transformation as she oscillates masochistically between the “inside” and the “outside” of her psychic borders, and between the symbolic and the semiotic. Furthermore, this enables Plath to develop the unique “Siren Voice of the Other.” In comparison, Sexton, the “dead/less,” evades any confrontation with the maternal and the performance of death in her poetry. Her case is further complicated by the discovery of a second mother. As a result, passivity becomes a main characteristic of her work. This passivity remains until the maternal abject bursts in her text and she reacts to this by performing cleansing rituals, and gravitating toward a symbolic father. Without the dynamism of transgression, Sexton’s work is heterogeneous but does not achieve ultimate transformation and jouissance. Confessional poetry, in this sense, takes on a new dimension. The life stories of the poets become important not for their pejorative, pathological aspects that focus on narrative mimesis, but rather for their manifestation as an aesthetic process. The subject of the writer becomes important as an aesthetic identity in the poems, which are rooted in real life. The main concern then becomes the aesthetic transformative dialectic between the semiotic and the symbolic in her work of art.Philadelphia University, Jorda

LISTENING TO THE SPONTANEOUS MUSIC-MAKING OF PRESCHOOL CHILDREN IN PLAY: LIVING A PEDAGOGY OF WONDER

This study sings with joy the wonder of preschool children spontaneously being music-makers in play. Through hermenuetic phenomenological methodology provided by van Manen (2003), voices of Heidegger (1962, being-with), Levin (1989, listening), Ihde (1976, music-language), Casey (1993, place), Merleau-Ponty (1962, the body), Levinas (1987, "we"), Arendt (1959, new beginnings), and Steiner (1984; 1985a,b; 1998, human development, freedom) support the work. The study asks: What is the lived experience of preschool children spontaneously making music in play? In Waldorf preschools, forty-six children in three age-differentiated classes are observed and tape-recorded in a pre-study; observations of twenty-four children in a mixed-age class and, during outdoor playtime, an additional twenty-four children from a similar class are observed and recorded in note-taking during a year-long study. Significant themes of will-ing, be-ing, and time-in-place emerge. Freedom to move about in play with peers is essential to music-making that spontaneously expresses Life-lived-in-the-moment. The phenomena of this study -- the songs, chant, and other sound-shapes -- are the being of children, who are not bound by time or by space. In this study, musical form includes a sung-tryptich, a communal-collage, call-response, a transforming chant, and language that sings and stretches into many, varied sound-shapes. The wonder of Life shines through. Teaching music of early childhood is being one's self a music-maker in being-with children. This teaching is preparing a place of beauty, order, and caring, where a rhythmic framework of fine- and living-arts experiences extends the letting-learn, and where the children move about, playing freely with materials that nurture the imagination, indoors and out daily, rain or shine. Teaching is moving through richly developed integrated-circles (songs, poems, and verses, with gestures), worthy of the children's imitation. Teaching is telling tales from the heart, planting seeds of wisdom. Teaching is "reading the children" then creating soft edges in moving-with-one's-own-singing from one activity to another. This is a Pedagogy of Wonder that respects the child's will, enriches the child's Being, lets-be the spontaneous music-making of preschool children in play, nourishing that music-making by being-with the child musically. Listening to the spontaneous music-making of preshcool children in play offers a new beginning