Cristiana Bentes

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This paper presents a parallel approach for solving the Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD). The parallel algorithm is embedded with a multi-start heuristic which consists of a variable neighborhood descent procedure, with a random neighborhood ordering (RVND), integrated in an iterated local search (ILS) framework. The(More)
In this paper we propose a novel software-only distributed sharedmemory system (SW-DSM), the Affinity Entry Consistency (AEC) protocol. The protocol is based on Entry Consistency but, unlike previous approaches, does not require the explicit association of shared data to synchronization variables, uses the page as its coherence unit, and generates the set(More)
Distributed systems such as clusters of PCs are low-cost alternatives for running parallel rendering systems, but they have high communication overhead, and limited memory capacity on each processing node. In this paper we focus on the strategy for distributing the parallel rendering work among the PCs. A good distribution strategy provides better load(More)
The tremendous computing power of Graphics Processing Units (GPUs) can be used to accelerate the evolution process in Genetic Programming (GP). The automatic generation of code using the GPU usually follows two different approaches: compiling each evolved or interpreting multiple programs. Both approaches, however, have performance drawbacks. In this work,(More)
Direct volume rendering of irregular 3D datasets demands high computational power and memory bandwidth. Recent research in optimizing volume rendering algorithms are exploring the high processing power offered by a new trend in hardware design: multithreaded accelerator devices. Accelerators like the Graphics Processing Units (GPU) and the Cell Broadband(More)
Ray-casting implementations require that the connectivity between the cells of the dataset to be explicitly computed and kept in memory. This constitutes a huge obstacle for obtaining real-time rendering for very large models. In this paper, we address this problem by introducing a new implementation of the ray-casting algorithm for irregular datasets. Our(More)
A dynamic swarm formation based in artificial potential fields is presented and extended to 3D environments. A dynamic technic to adjust the swarm configuration when avoiding obstacles is also proposed. Using potential fields in conjunction with a global planner like the A* algorithm allows the navigation through an environment in presence of obstacles. The(More)
Direct volume rendering has become a popular technique for visualizing volumetric data from sources such as scientific simulations, analytic functions, medical scanners, among others. Volume rendering algorithms, such as raycasting, can produce high-quality images, however, the use of raycasting has been limited due to its high demands on computational(More)
The overwhelming options conveyed by Internet exaggerated growth bring new issues for users engaged in buying and/or selling goods using the net as the business medium. Goods and services can be exchanged, directly sold or negotiated in auctions. In any of these situations, finding the required product by the right price is the big challenge for Internet(More)