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A Design of Automatic Visualizations for Divide-and-Conquer Algorithms
(Universidad Rey Juan Carlos, 2008-07) Velázquez Iturbide, J. Ángel; Pérez Carrasco, Antonio; Urquiza Fuentes, Jaime
The paper addresses the design of program visualizations adequate to represent divide-and-conquer algorithms. Firstly, we present the results of several surveys performed on the visualization of divide-and-conquer algorithms in the literature. Secondly, we make a proposal for three complementary, coordinated views of these algorithms. In summary, they are based an animation of the activation tree, an animation of the data structure, and a sequence of visualizations of the substructures, respectively.
A Learning Algorithm for Energy-Efficient Routing of Prioritized Messages in Wireless Sensor Networks
(2007-10-01T08:52:49Z) Arroyo-Valles, Rocio; Garcia Marques, Antonio; Cid Sueiro, Jesús
Energy is a valuable resource in wireless sensor networks since it constitutes a limiting factor for the network lifetime. In order to make an efficient use of its own energy resources, each node in the network should be aware of the energy resources at other nodes, which can be relevant to the success of their routing decisions. The proposal of this paper is twofold:(i)to design a routing algorithm based on learning patterns using geographic information and (ii) to focus on the cut down in energy consumption. We show that by exploiting local information from the signals detected at each node, sensor nodes can learn to route messages in order to improve the communication performance of the overall network and minimize the need of coordination or signalling protocols among nodes. Moreover, if messages are prioritized by some importance parameter, the overall importance of the successfully transmitted messages can be drastically improved. Experimental results highlight that our algorithm achieves a good performance in terms of successful delivery rate and maximizes the importance of the received messages.
An evaluation of the effortless approach to build algorithm animations with WinHIPE
(Università Degli Studi di Firenze, 2006-06) Urquiza Fuentes, Jaime; Velázquez Iturbide, J. Ángel
Un asistente extensible para la experimentación interactiva con problemas combinatorios
(2010-09) Velázquez-Iturbide, J. Ángel; Debdi, Ouafae; Gómez García, Daniel; Fresno Ramírez, Jesús del; Rubio Sánchez, Manuel; Paredes Velasco, Maximiliano
Los algoritmos voraces tienen un problema desde el punto de vista docente: no son muy adecuados para su ejercitación por los alumnos. Para remediar esta situación, hemos diseñado un enfoque didáctico basado en experimentación y soportado por varios asistentes interactivos para problemas concretos (mochila, selección de actividades, árbol de recubrimiento de coste mínimo). A partir de nuestra experiencia, la comunicación analiza los problemas encontrados y presenta mejoras en varios aspectos. Primero, hemos ampliado ligeramente el método experimental. Segundo, hemos modificado los asistentes interactivos para soportar mejor el método experimental e incluso poder usarlo con otras técnicas de diseño (programación dinámica, algoritmos aproximados). Tercero, hemos integrado dos asistentes interactivos en uno solo, llamado GreedEx, que puede ampliarse para dar soporte a otros problemas combinatorios. Por último, hemos ampliado GreedEx con un tercer problema, el de la mochila 0/1. En resumen, estas mejoras han reducido las limitaciones del método experimental, han ampliado el dominio de aplicación de los asistentes, y facilitan su extensión a otros problemas y su mantenimiento.
Energy-efficient Selective Forwarding for Sensor Networks
(2008-06-01T09:24:16Z) Arroyo-Valles, Rocio; Garcia Marques, Antonio; Cid Sueiro, Jesús
In this paper a new energy-efficient scheme for data transmission in wireless sensor networks is proposed. It is based on the idea of selective forwarding: sensor nodes only transmit the most relevant messages, discarding the least important ones. To do so, messages are assumed to be graded with an importance value, and a forwarding threshold, which depends on the sensor consumption patterns, the available energy resources and the information obtained from the neighborhood, is applied to these values. In this approach, the sensor decision also depends on the expected behavior of neighboring nodes, so as to maximize not only the transmission efficiency, but also the performance of the whole communication up to the estination node. Simulation results show that the proposed scheme increases the network lifetime, and maximizes the global importance of the messages received by the sink node. Index Terms¿selective forwarding, energy-efficiency, message importance, sensor networks.
GRASP con Path Relinking para el problema del SumCut
(MAEB, 2012) Sánchez-Oro, Jesús; Duarte, Abraham
En este artículo se propone un algoritmo GRASP combinado con Path Relinking para resolver el problema de minimización del SumCut. En el problema del SumCut, a partir de un grafo de n nodos es necesario etiquetar todos los nodos de forma que ca- da uno de ellos reciba una etiqueta única del conjunto f1; 2;
H-Isoefficiency: Scalability Metric for Heterogeneous Systems
(J. Vigo - Aguiar, 2010-06) Bosque, Jose Luis; Robles, Oscar D.; Toharia, Pablo; Pastor, Luis
Scalability is one of the most important features in exascale computing. Most of this systems are heterogeneous and therefore it becomes necessary to develop models and metrics that take into account this heterogeneity. This paper presents a new expression of the isoefficiency function called H-isoefficiency. This function can be applied for both homogeneous and heterogeneous systems and allows to analyze the scalability of a parallel system. Then, as an example, a theoretical a priori analysis of the scalability of Floyd¿s algorithm is presented. Finally a model evaluation which demonstrate the correlation between the theoretical analysis and the experimental results is showed.
Path Efficiency in Mobile Ad-Hoc Networks
(3rd International Symposium on Wireless Communication Systems, 2006. ISWCS '06, 2006-09) Caamaño, Antonio J.; Vinagre Díaz, Juan José; Mora Jiménez, Inma; Figuera Pozuelo, Carlos; Ramos, Javier
The process of routing in large ad-hoc mobile networks is theoretically analyzed as the capacity of a packet to be directed form a source to a destination. The equivalence between directivity and an effective radius, which represents the actual knowledge of any node of its neighbourhood, is demonstrated. The mobility of the network is modelled as that resulting from the most probable distribution of mobile nodes. The results are conclusive: mobility reduces the throughput and delay performance of any routing algorithm with a finite effective radius.
Pedagogical Effectiveness of Engagement Levels - A Survey of Successful Experiences
(Universidad Rey Juan Carlos, 2008-07) Urquiza Fuentes, Jaime; Velázquez Iturbide, J. Ángel
In this paper we survey experiments with program and algorithm visualizations (PAVs) where learning improvements have been detected. We analyze these experiments based on the student's level of engagement with the visualizations. There are some features present in most of these, successful, experiments. Therefore they should be taken into account as important factors affecting pedagogical effectiveness of PAVs, these features are: narrative and textual contents, feedback to students' answers and a student centered approach when designing PAV construction kits.
Power-Efficient OFDM with Reduced Complexity and Feedback Overhead
(2006-05-01T11:04:53Z) Garcia Marques, Antonio; Digham, Fadel F.; Giannakis, Georgios B.
Motivated by the increasing demand for low-cost low-power wireless sensor networks and related applications, we develop suboptimal but simple bit and power loading algorithms that minimize transmit-power for orthogonal frequency division multiplexing (OFDM) under rate and error probability constraints. Bit and power loading adaptation are based on a quantized version of channel state information (D-CSI) conveyed from the receiver to the transmitter. Our design exploits the correlation among sub-carriers in order to reduce feedback overhead. Numerical examples support our claim that simple suboptimal schemes with a reduced number of feedback bits achieve near-optimal performance while providing significant power savings.
Resultado de las tres primeras evaluaciones de usabilidad de SRec
(Universidad Rey Juan Carlos, 2009-05) Pérez Carrasco, Antonio; Velázquez Iturbide, Ángel
Se presentan las tres primeras sesiones de evaluación de usabilidad realizadas sobre SRec, una herramienta software con fines docentes orientada tanto a profesores como alumnos. Se persigue con estas sesiones por un lado evaluar el desarrollo realizado y por otro obtener información sobre qué funciones son más y menos útiles para el alumnado, al cual la aplicación intenta ayudar en el estudio de los algoritmos en función de la técnica de diseño empleada para desarrollarlos.
SRec 1.2: visualizador integrado de programas recursivos generales y de Divide y Vencerás
(Actas SIIE 2009, 2009-09) Velázquez Iturbide, Ángel; Pérez Carrasco, Antonio
En esta comunicación presentamos una herramienta software, SRec, que permite desarrollar de manera automatizada la visualización animada de programas con múltiples opciones de interactividad y configuración que permiten aumentar la implicación y éxito del alumno en el aprendizaje de los algoritmos recursivos y diseñados bajo la técnica de ¿Divide y vencerás¿.

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Examinando Comunicaciones a Congresos por Materia "1203.02 Lenguajes Algorítmicos"