Parallelism in declarative languages

Imperative programming languages were initially built for uniprocessor systems that evolved out of the Von Neumann machine model. This model of storage oriented computation blocks parallelism and increases the cost of parallel program development and porting. Declarative languages based on mathematical models of computation, seem more suitable for the development of parallel programs. In the first part of this thesis we examine different language families under the declarative paradigm: functional, logic, and constraint languages. Functional languages are based on the abstract model of functions and (lamda)-calculus. They were initially developed for symbolic computation, but today they are commonly used in numerical analysis and many other application areas. Pure lisp is a widely known member of this class. Logic languages are based on first order predicate calculus. Although they were initially developed for theorem proving, fifth generation operating systems are written in them. Most logic languages are descendants or distant relatives of Prolog. Constraint languages are related to logic languages. In a constraint language you define a program object by placing constraints on its structure and its behavior. They were initially used in graphics applications, but today researchers work on using them in parallel computation. Here we will compare and contrast the language classes above, locate advantages and deficiencies, and explain different choices made by language implementors. In the second part of thesis we describe a front end for the CONSUL, a prototype constraint language for programming multiprocessors. The most important features of the front end are compact representation of constraints, type definitions, functional use of relations, and the ability to split programs into multiple files

Coarse-grained parallel genetic algorithms: Three implementations and their analysis

Although solutions to many problems can be found using direct analytical methods such as those calculus provides, many problems simply are too large or too difficult to solve using traditional techniques. Genetic algorithms provide an indirect approach to solving those problems. A genetic algorithm applies biological genetic procedures and principles to a randomly generated collection of potential solutions. The result is the evolution of new and better solutions. Coarse-Grained Parallel Genetic Algorithms extend the basic genetic algorithm by introducing genetic isolation and distribution of the problem domain. This thesis compares the capabilities of a serial genetic algorithm and three coarse-grained parallel genetic algorithms (a standard parallel algorithm, a non-uniform parallel algorithm and an adaptive parallel algorithm). The evaluation is done using an instance of the traveling salesman problem. It is shown that while the standard course-grained parallel algorithm provides more consistent results than the serial genetic algorithm, the adaptive distributed algorithm out-performs them both. To facilitate this analysis, an extensible object-oriented library for genetic algorithms, encompassing both serial and coarse-grained parallel genetic algorithms, was developed. The Java programming language was used throughout

Multi-perspective modelling for knowledge management and knowledge engineering

ii It seems almost self-evident that “knowledge management ” and “knowledge engineering” should be related disciplines that may share techniques and methods between them. However, attempts by knowledge engineers to apply their techniques to knowledge management have been praised by some and derided by others, who claim that knowledge engineers have a fundamentally wrong concept of what “knowledge management” is. The critics also point to specific weaknesses of knowledge engineering, notably the lack of a broad context for the knowledge. Knowledge engineering has suffered some criticism from within its own ranks, too, particularly of the “rapid prototyping ” approach, in which acquired knowledge was encoded directly into an iteratively developed computer system. This approach was indeed rapid, but when used to deliver a final system, it became nearly impossible to verify and validate the system or to maintain it. A solution to this has come in the form of knowledge engineering methodology, and particularly in the CommonKAD

TALK COMMONSENSE TO ME! ENRICHING LANGUAGE MODELS WITH COMMONSENSE KNOWLEDGE

Human cognition is exciting, it is a mesh up of several neural phenomena which really strive our ability to constantly reason and infer about the involving world. In cognitive computer science, Commonsense Reasoning is the terminology given to our ability to infer uncertain events and reason about Cognitive Knowledge. The introduction of Commonsense to intelligent systems has been for years desired, but the mechanism for this introduction remains a scientific jigsaw. Some, implicitly believe language understanding is enough to achieve some level of Commonsense [90]. In a less common ground, there are others who think enriching language with Knowledge Graphs might be enough for human-like reasoning [63], while there are others who believe human-like reasoning can only be truly captured with symbolic rules and logical deduction powered by Knowledge Bases, such as taxonomies and ontologies [50]. We focus on Commonsense Knowledge integration to Language Models, because we believe that this integration is a step towards a beneficial embedding of Commonsense Reasoning to interactive Intelligent Systems, such as conversational assistants. Conversational assistants, such as Alexa from Amazon, are user driven systems. Thus, giving birth to a more human-like interaction is strongly desired to really capture the user’s attention and empathy. We believe that such humanistic characteristics can be leveraged through the introduction of stronger Commonsense Knowledge and Reasoning to fruitfully engage with users. To this end, we intend to introduce a new family of models, the Relation-Aware BART (RA-BART), leveraging language generation abilities of BART [51] with explicit Commonsense Knowledge extracted from Commonsense Knowledge Graphs to further extend human capabilities on these models. We evaluate our model on three different tasks: Abstractive Question Answering, Text Generation conditioned on certain concepts and aMulti-Choice Question Answering task. We find out that, on generation tasks, RA-BART outperforms non-knowledge enriched models, however, it underperforms on the multi-choice question answering task. Our Project can be consulted in our open source, public GitHub repository (Explicit Commonsense).A cognição humana é entusiasmante, é uma malha de vários fenómenos neuronais que nos estimulam vivamente a capacidade de raciocinar e inferir constantemente sobre o mundo envolvente. Na ciência cognitiva computacional, o raciocínio de senso comum é a terminologia dada à nossa capacidade de inquirir sobre acontecimentos incertos e de raciocinar sobre o conhecimento cognitivo. A introdução do senso comum nos sistemas inteligentes é desejada há anos, mas o mecanismo para esta introdução continua a ser um quebra-cabeças científico. Alguns acreditam que apenas compreensão da linguagem é suficiente para alcançar o senso comum [90], num campo menos similar há outros que pensam que enriquecendo a linguagem com gráfos de conhecimento pode serum caminho para obter um raciocínio mais semelhante ao ser humano [63], enquanto que há outros ciêntistas que acreditam que o raciocínio humano só pode ser verdadeiramente capturado com regras simbólicas e deduções lógicas alimentadas por bases de conhecimento, como taxonomias e ontologias [50]. Concentramo-nos na integração de conhecimento de censo comum em Modelos Linguísticos, acreditando que esta integração é um passo no sentido de uma incorporação benéfica no racíocinio de senso comum em Sistemas Inteligentes Interactivos, como é o caso dos assistentes de conversação. Assistentes de conversação, como o Alexa da Amazon, são sistemas orientados aos utilizadores. Assim, dar origem a uma comunicação mais humana é fortemente desejada para captar realmente a atenção e a empatia do utilizador. Acreditamos que tais características humanísticas podem ser alavancadas por meio de uma introdução mais rica de conhecimento e raciocínio de senso comum de forma a proporcionar uma interação mais natural com o utilizador. Para tal, pretendemos introduzir uma nova família de modelos, o Relation-Aware BART (RA-BART), alavancando as capacidades de geração de linguagem do BART [51] com conhecimento de censo comum extraído a partir de grafos de conhecimento explícito de senso comum para alargar ainda mais as capacidades humanas nestes modelos. Avaliamos o nosso modelo em três tarefas distintas: Respostas a Perguntas Abstratas, Geração de Texto com base em conceitos e numa tarefa de Resposta a Perguntas de Escolha Múltipla . Descobrimos que, nas tarefas de geração, o RA-BART tem um desempenho superior aos modelos sem enriquecimento de conhecimento, contudo, tem um desempenho inferior na tarefa de resposta a perguntas de múltipla escolha. O nosso Projecto pode ser consultado no nosso repositório GitHub público, de código aberto (Explicit Commonsense)

Memory abstractions for parallel programming

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 156-163).A memory abstraction is an abstraction layer between the program execution and the memory that provides a different "view" of a memory location depending on the execution context in which the memory access is made. Properly designed memory abstractions help ease the task of parallel programming by mitigating the complexity of synchronization or admitting more efficient use of resources. This dissertation describes five memory abstractions for parallel programming: (i) cactus stacks that interoperate with linear stacks, (ii) efficient reducers, (iii) reducer arrays, (iv) ownershipaware transactions, and (v) location-based memory fences. To demonstrate the utility of memory abstractions, my collaborators and I developed Cilk-M, a dynamically multithreaded concurrency platform which embodies the first three memory abstractions. Many dynamic multithreaded concurrency platforms incorporate cactus stacks to support multiple stack views for all the active children simultaneously. The use of cactus stacks, albeit essential, forces concurrency platforms to trade off between performance, memory consumption, and interoperability with serial code due to its incompatibility with linear stacks. This dissertation proposes a new strategy to build a cactus stack using thread-local memory mapping (or TLMM), which enables Cilk-M to satisfy all three criteria simultaneously. A reducer hyperobject allows different branches of a dynamic multithreaded program to maintain coordinated local views of the same nonlocal variable. With reducers, one can use nonlocal variables in a parallel computation without restructuring the code or introducing races. This dissertation introduces memory-mapped reducers, which admits a much more efficient access compared to existing implementations. When used in large quantity, reducers incur unnecessarily high overhead in execution time and space consumption. This dissertation describes support for reducer arrays, which offers the same functionality as an array of reducers with significantly less overhead. Transactional memory is a high-level synchronization mechanism, designed to be easier to use and more composable than fine-grain locking. This dissertation presents ownership-aware transactions, the first transactional memory design that provides provable safety guarantees for "opennested" transactions. On architectures that implement memory models weaker than sequential consistency, programs communicating via shared memory must employ memory-fences to ensure correct execution. This dissertation examines the concept of location-based memoryfences, which unlike traditional memory fences, incurs latency only when synchronization is necessary.by I-Ting Angelina Lee.Ph.D