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Publicações

Publicações por CRACS

2009

Improving the automatic evaluation of problem solutions in programming contests

Autores
Ribeiro, P; Guerreiro, P;

Publicação
Olympiads in Informatics

Abstract
Automatically evaluating source program files is a crucial part of programming contests. The evaluation aims at discriminating programs according to their correctness and efficiency. Given the performance of today's computers, in order to be able to distinguish the complexity of solutions, it is often necessary to use very large data sets. This is awkward, because it is against the nature of the stated problem and puts an unintended burden on the input operations. Besides, by advertizing a limit for the size of the input, the problem description gives away information with which the contestants may guess the algorithmic complexity that their solutions must attain. It would be more realistic to omit that information and let the contestants discover the limits by analyzing the problem, using a scientific approach. The complexity of the solution can then be estimated automatically by measuring the execution time of the function that solves the problem in incremental test cases, and plotting it against the size of the input. By calling the function multiple times and taking the overall time, we may use only data files the size of which is related to the nature of the problem being solved. © 2009 Institute of Mathematics and Informatics, Vilnius.

2009

Teaching artificial intelligence and logic programming in a competitive environment [Dirbtinio intelekto ir loginio programavimo mokymas konkurencingoje aplinkoje]

Autores
Ribeiro, P; Simoes, H; Ferreira, M;

Publicação
Informatics in Education

Abstract
Motivation plays a key role in the learning process. This paper describes an experience in the context of undergraduate teaching of Artificial Intelligence at the Computer Science Department of the Faculty of Sciences in the University of Porto. A sophisticated competition framework, which involved Prolog programmed contenders and game servers, including an appealing GUI, was developed to motivate students on the deepening of the topics covered in class. We report on the impact that such a competitive setup caused on students' commitment, which surpassed our most optimistic expectations. © 2009 Institute of Mathematics and Informatics, Vilnius.

2009

EduMCA: An approach to educational mobile content adaptation

Autores
Queiros, R; Pinto, MP;

Publicação
Actas da 4a Conferencia Iberica de Sistemas e Tecnologias de Informacao, CISTI 2009

Abstract
As the variety of mobile devices connected to the Internet grows, there is a corresponding increase in the need to deliver content tailored to their heterogeneous characteristics. At the same time, we watch to the increase of eLearning in universities through the adoption of electronic platforms and standards. Not surprisingly, the concept of mLearning (Mobile Learning) appeared in recent years decreasing the limitation of learning location with the mobility of general portable devices. However, this large number and variety of Web-enabled devices poses several challenges for Web content creators who want to automatic get the delivery context and adapt the content to the client mobile devices. In this paper we analyze several approaches to defining delivery context and present an architecture for deliver uniform mLearning content to mobile devices denominated eduMCA-Educational Mobile Content Adaptation. With the eduMCA system the Web authors will not need to create specialized pages for each kind of device, since the content is automatically transformed to adapt to any mobile device capabilities from WAP to XHTML MP-compliant devices.

2009

Viability-based computation of spatially constrained minimum time trajectories for an autonomous underwater vehicle: implementation and experiments

Autores
Tinka, A; Diemer, S; Madureira, L; Marques, EB; de Sousa, JB; Martins, R; Pinto, J; da Silva, JE; Sousa, A; Saint Pierre, P; Bayen, AM;

Publicação
2009 AMERICAN CONTROL CONFERENCE, VOLS 1-9

Abstract
A viability algorithm is developed to compute the constrained minimum time function for general dynamical systems. The algorithm is instantiated for a specific dynamics (Dubin's vehicle forced by a flow field) in order to numerically solve the minimum time problem. With the specific dynamics considered, the framework of hybrid systems enables us to solve the problem efficiently. The algorithm is implemented in C using epigraphical techniques to reduce the dimension of the problem. The feasibility of this optimal trajectory algorithm is tested in an experiment with a Light Autonomous Underwater Vehicle (LAUV) system. The hydrodynamics of the LAUV are analyzed in order to develop a low-dimension vehicle model. Deployment results from experiments performed in the Sacramento River in California are presented, which show good performance of the algorithm.

2009

Distributed, Modular HTL

Autores
Henzinger, TA; Kirsch, CM; Marques, ERB; Sokolova, A;

Publicação
2009 30TH IEEE REAL-TIME SYSTEMS SYMPOSIUM, PROCEEDINGS

Abstract
The Hierarchical Timing Language (HTL) is a real-time coordination language for distributed control systems. HTL programs must be checked for well-formedness, race freedom, transmission safety (schedulability of inter-host communication), and time safety (schedulability of host computation). We present a modular abstract syntax and semantics for HTL, modular checks of well-formedness, race freedom, and transmission safety, and modular code distribution. Our contributions here complement previous results on HTL time safety and modular code generation. Modularity in HTL can be utilized in easy program composition as well as fast program analysis and code generation, but also in so-called runtime patching, where program components may be modified at runtime.

2009

IMC: A Communication Protocol for Networked Vehicles and Sensors

Autores
Martins, R; Dias, PS; Marques, ERB; Pinto, J; Sousa, JB; Pereira, FL;

Publicação
OCEANS 2009 - EUROPE, VOLS 1 AND 2

Abstract
This paper presents the Inter-Module Communication (IMC) protocol, a message-oriented protocol designed and implemented in the Underwater Systems and Technology Laboratory (LSTS) to build interconnected systems of vehicles, sensors and human operators that are able to pursue common goals cooperatively by exchanging real-time information about the environment and updated objectives. IMC abstracts hardware and communication heterogeniety by providing a shared set of messages that can be serialized and transferred over different means. The described protocol contrasts with other existing application level protocols by not imposing or assuming a specific software architecture for client applications. Native support can be automatically generated for different programming languages and/or computer architectures resulting in optimized code which can be used both for networked nodes and also for inter-process and inter-thread communication. The protocol has already been tested throughout various experiments led by LSTS where it has taken care of communications between vehicles, sensors and operator consoles. We are now developing the protocol in the direction of having multi-vehicle cooperation using live data from environmental sensors and mixed-initiative user interaction.

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