1,195 research outputs found
Binding-Time Analysis for Mercury
Full text linkIn this work, we develop a binding-time analysis for the logic programming language Mercury. We introduce a precise domain of binding-times, based on the type information available in Mercury programs, that allows the analyser to reason with partially static data structures. The analysis is polyvariant, and deals with the module structure and higher-order capabilities of Mercury programs.status: Publishe
Offline Specialisation in Prolog Using a Hand-Written Compiler Generator
Full text linkThe so called "cogen approach" to program specialisation, writing a compiler generator instead of a specialiser, has been used with considerable success in partial evaluation of both functional and imperative languages. This paper demonstrates that the "cogen" approach is also applicable to the specialisation of logic programs (called partial deduction when applied to pure logic programs) and leads to effective specialisers. Moreover, using good binding-time annotations, the speed-ups of the specialised programs are comparable to the speed-ups obtained with online specialisers. The paper first develops a generic approach to offline partial deduction and then a specific offline partial deduction method, leading to the offline system LIX for pure logic programs. While this is a usable specialiser by itself, its specialisation strategy is used to develop the "cogen" system LOGEN. Given a program, a specification of what inputs will be static, and an annotation specifying which calls should be unfolded, LOGEN generates a specialised specialiser for the program at hand. Running this specialiser with particular values for the static inputs results in the specialised program. While this requires two steps instead of one, the efficiency of the specialisation process is improved in situations where the same program is specialised multiple times. The paper also presents and evaluates an automatic binding-time analysis that is able to derive the annotations. While the derived annotations are still suboptimal compared to hand-crafted ones, they enable non-expert users to use the LOGEN system in a fully automated way Finally, LOGEN is extended so as to directly support a large part of Prolog's declarative and non-declarative features and so as to be able to perform so called mixline specialisations. In mixline specialisation some unfolding decisions depend on the outcome of tests performed at specialisation time instead of being hardwired into the specialiser
Specializing interpreters using offline partial deduction
No full textWe present the latest version of the LOGEN partial evaluation system for logic programs. In particular we present new binding-types, and show how they can be used to effectively specialise a wide variety of interpreters. We show how to achieve Jones-optimality in a systematic way for several interpreters. Finally, we present and specialise a non-trivial interpreter for a small functional programming language. Experimental results are also presented, highlighting that the LOGEN system can be a good basis for generating compilers for high-level languages
Anti-Unification of Unordered Goals
Full text linkAnti-unification in logic programming refers to the process of capturing common syntactic structure among given goals, computing a single new goal that is more general called a generalization of the given goals. Finding an arbitrary common generalization for two goals is trivial, but looking for those common generalizations that are either as large as possible (called largest common generalizations) or as specific as possible (called most specific generalizations) is a non-trivial optimization problem, in particular when goals are considered to be unordered sets of atoms. In this work we provide an in-depth study of the problem by defining two different generalization relations. We formulate a characterization of what constitutes a most specific generalization in both settings. While these generalizations can be computed in polynomial time, we show that when the number of variables in the generalization needs to be minimized, the problem becomes NP-hard. We subsequently revisit an abstraction of the largest common generalization when anti-unification is based on injective variable renamings, and prove that it can be computed in polynomially bounded time
Towards a framework for goal revision
No full textA rational agent revises its goals if something changes in its mental state. In this paper, we propose (i) a general framework based on classical propositional logic, to represent changes in the mental state of the agent after the acquisition of new information and/or after the arising of new desires; (ii) fundamental postulates that the function which generates the goal set must obey; and (iii) properties that this function must have to guarantee both the agent's maximal satisfaction and the consistency of the goal set
Attitudes Toward Statistics and Their Relationship with Short- and Long-Term Exam Results
Full text linkThis study uses the Attitudes Toward Statistics (ATS) scale (Wise 1985) to investigate the attitudes toward statistics and the relationship of those attitudes with short- and long-term statistics exam results for university students taking statistics courses in a five year Educational Sciences curriculum. Compared to the findings from previous studies, the results indicate that the sample of undergraduate students have relatively negative attitudes toward the use of statistics in their field of study but relatively positive attitudes toward the course of statistics in which they are enrolled. Similar to other studies, we find a relationship between the attitudes toward the course and the results on the first year statistics exam. Additionally, we investigate the relationship between the attitudes and the long-term exam results. A positive relationship is found between students' attitudes toward the use of statistics in their field of study and the dissertation grade. This relationship does not differ systematically from the one between the first year statistics exam results and the dissertation grade in the fifth year. Thus, the affective and cognitive measures at the beginning of the curriculum are, equally predictive for long-term exam results. Finally, this study reveals that the relationship between attitudes toward statistics and exam results is content-specific: We do not find a relationship between attitudes and general exam results, only between attitudes and results on statistics exams. Copyright © 2006 by Stijn Vanhoof, Ana Elisa Castro Sotos, Patrick Onghena, Lieven Verschaffel, Wim Van Dooren, Wim Van den Noortgate all rights reserved.sponsorship: This research was partially supported by Grant GOA 2006/01 "Developing adaptive expertise in mathematics education" from the Research Fund Katholieke Universiteit Leuven, Belgium. (Research Fund Katholieke Universiteit Leuven, Belgium|GOA 2006/01)status: Publishe
Dealing with the Energy Versus Performance Tradeoff in Future CMOS Digital Circuit Design
No full textstatus: Publishe
Floating WIM Threshold Concept for Truck Weight Enforcement
Full text linkWeigh stations are the primary weight compliance checkpoints for commercial trucks. In the past several decades, states have used weigh-in-motion (WIM) technology to reduce delay and increase enforcement on overweight vehicles. This study offers a detailed analysis of weigh station systems and presents floating-threshold algorithms to improve the efficiency of WIM equipped weigh stations.
This research evaluates weigh station design and operational parameters using queueing theory and found that WIM technology not only enhances the effectiveness and efficiency of weigh station operations but also largely reduces travel delay for trucking companies. The effects of truck demand, truck weight distribution, static scale service time, WIM accuracy, and sorting threshold on weigh station operations have been analyzed. The author shows the importance of transponders in a WIM mainline weigh station operation. The author also proves that the increase of storage spaces within a weigh station may largely increase truck travel delay and does not significantly improve weigh station operations.
This research focuses on the development of floating-threshold algorithms. Since the number of trucks, particularly heavy trucks, has increased rapidly in recent decades, many weigh stations cannot meet the demand even when equipped with WIM systems. This problem is complicated by the fact that truck demands, truck weight distribution, and static scale service time vary by time of day and day of week. The author designed floating-threshold algorithms to automatically adapt to high truck demand and the varying of truck demand, truck weight distribution, and static scale service time, over time. When the queue at the weigh station is long, the threshold value is increased so as to avoid the closure of the weigh station while still catching the worst weight limit offenders. When the queue is short, the threshold value is lowered to increase the number of trucks inspected. Both the traditional fixed-threshold strategy and two floating-threshold strategies were modeled and tested using a microscopic simulation model. The results show that floating-threshold strategies are both more effective in weight enforcement and more efficient for heavy traffic flow and high-variance environments. The finding that different floating-threshold strategies have different effects indicates that it is necessary to make a further study on floating-threshold algorithms
The Impact of Tourism on Curacao's Economy: A Scenario Approach
No full textCuraçao is an autonomous countrywithin the Kingdom of the Netherlands. The governmentwants to support tourism development. However,various development strategies are possible. This articlepresents four scenarios of marketing and investmentstrategies that will affect the number of tourists fromThe Netherlands and North America (USA and Canada)in different ways. A multiplier model was used to calculatethe economic impacts of the four scenarios. Bydoing so, this article shows how the government’s decisionto support particular marketing and investmentstrategies may have certain outcomes for the number ofjobs in Curaçao’s tourism industry
Model Validation and New Water Control Strategies in Drinking Water Treatment Plant Wim Mensink
No full textStimela is an environment for standardized mathematical models of drinking water treatment processes. It can be used to predict the future water treatment situation which may happen or change. In water treatment plant Wim Mensink, the Stimela model train was set up to compare with other alternative water control strategies. Before starting the work of developing new water control strategies with Stimela model, Stimela model for Wim Mensink must be validated so that the model can be seen as a reliable and stable tool for the next work. Before the validation work, the current water control strategy for the treatment process needs to be investigated clearly to fulfil all the input control information is correct. Besides this, an experiment for obtaining the measured results of pellet diameters over different layers was performed in Wim Mensink. The validation work starts with single pellet softening process for three different reactors over first month from January 20th to February 20th. The fluidized bed height, pressure drop over total height of reactor, pellet diameters and porosities are validated. After that, the validation work is integrated with whole water treatment system to prove the function of pellet softening reactor and the four important water quality parameters over two important locations (after weir aerator location and final RO mixing location). The validated results of softening process are analysed by the relative error way to prove the reliability of the model results compared with measured results. The final step of the thesis work is developing the new water control strategies to optimize the current control plans of Wim Mensink. Five different water control strategies are put forward. They can be either reached separately according to their own advantages and limitations or fulfil with a step by step order as a whole optimization process. Moreover, the other water control strategies developed by engineering consultancy company DHV are evaluated here with Stimela model so that they can be proved reliable and achievable. In the future, the application of Stimela model will be spread over all the drinking water treatment plants in the Netherlands and contributes to the central automated control as a drinking water treatment operator training simulator.Sanitary EngineeringWatermanagementCivil Engineering and Geoscience
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