Search results for "HEURISTICS"

A Simulation-based Performance Evaluation of Heuristics for Dew Computing

2021

A Task Execution Scheme for Dew Computing with State-of-the-Art Smartphones

2021

The computing resources of today’s smartphones are underutilized most of the time. Using these resources could be highly beneficial in edge computing and fog computing contexts, for example, to support urban services for citizens. However, new challenges, especially regarding job scheduling, arise. Smartphones may form ad hoc networks, but individual devices highly differ in computational capabilities and (tolerable) energy usage. We take into account these particularities to validate a task execution scheme that relies on the computing power that clusters of mobile devices could provide. In this paper, we expand the study of several practical heuristics for job scheduling including executi…

The limits of visual mass perception

2009

The theory of direct perception suggests that observers can accurately judge the mass of a box picked up by a lifter shown in a point-light display. However, accurate perceptual performance may be limited to specific circumstances. The purpose of the present study was to systematically examine the factors that determine perception of mass, including display type, lifting speed, response type, and lifter's strength. In contrast to previous research, a wider range of viewing manipulations of point-light display conditions was investigated. In Experiment 1, we first created a circumstance where observers could accurately judge lifts of five box masses performed by a lifter of average strength…

Audiovisual Integration of Time-to-Contact Information for Approaching Objects.

2018

Previous studies of time-to-collision (TTC) judgments of approaching objects focused on effectiveness of visual TTC information in the optical expansion pattern (e.g., visual tau, disparity). Fewer studies examined effectiveness of auditory TTC information in the pattern of increasing intensity (auditory tau), or measured integration of auditory and visual TTC information. Here, participants judged TTC of an approaching object presented in the visual or auditory modality, or both concurrently. TTC information provided by the modalities was jittered slightly against each other, so that auditory and visual TTC were not perfectly correlated. A psychophysical reverse correlation approach was us…

A GRASP algorithm for constrained two-dimensional non-guillotine cutting problems

2005

This paper presents a greedy randomized adaptive search procedure (GRASP) for the constrained two-dimensional non-guillotine cutting problem, the problem of cutting the rectangular pieces from a large rectangle so as to maximize the value of the pieces cut. We investigate several strategies for the constructive and improvement phases and several choices for critical search parameters. We perform extensive computational experiments with well-known instances previously reported, first to select the best alternatives and then to compare the efficiency of our algorithm with other procedures.

On the generalized directed rural postman problem

2014

The generalized directed rural postman problem (GDRPP) is a generic type of arc routing problem. In the present paper, it is described how many types of practically relevant single-vehicle routing problems can be modelled as GDRPPs. This demonstrates the versatility of the GDRPP and its importance as a unified model for postman problems. In addition, an exact and a heuristic solution method are presented. Computational experiments using two large sets of benchmark instances are performed. The results show high solution quality and thus demonstrate the practical usefulness of the approach.

Constructing Good Solutions for the Spanish School Timetabling Problem

1996

In the school timetabling problem a set of lessons (combinations of classes, teachers, subjects and rooms) has to be scheduled within the school week. Considering classes, teachers and rooms as resources for the lessons, the problem may be viewed as the scheduling of a project subject to resource constraints. We have developed an algorithm with three phases. In Phase I an initial solution is built by using the scheme of parallel heuristic algorithm with priority rules, but imbedding at each period the construction of a maximum cardinality independent set on a resource graph. In Phase II a tabu search procedure starts from the solution of Phase I and obtains a feasible solution to the proble…

Tabu search algorithms for an industrial multi-product and multi-objective assembly line balancing problem, with reduction of the task dispersion

2002

This paper presents a real-world industrial application of the multi-product and multi-objective assembly line balancing problem, for a company involved in the production of four models of a white goods product. The problem solved is a GALBP-2, with 10 workstations and multiple objectives (to maximize the production rate in order to deal with an increase of the demand forecasted, to reach an equal cycle time of all the models and an equal workload of the different workstations, and finally, to minimize the dispersion of worker tasks on each one of the different models-the common tasks of the different models at the same workstation). The paper presents an integrated approach based on four h…

Heuristic solutions to the problem of routing school buses with multiple objectives

2002

In this paper we address the problem of routing school buses in a rural area. We approach this problem with a node routing model with multiple objectives that arise from conflicting viewpoints. From the point of view of cost, it is desirable to minimise the number of buses used to transport students from their homes to school and back. From the point of view of service, it is desirable to minimise the time that a given student spends en route. The current literature deals primarily with single-objective problems and the models with multiple objectives typically employ a weighted function to combine the objectives into a single one. We develop a solution procedure that considers each objecti…

Labour Scheduling at an Airport Refuelling Installation

1999

We have developed an automatic assignment procedure for labour scheduling at a continously operating airport refuelling installation. Different types of workers are subject to different conditions on the shifts they can do (morning, evening or night), shift lengths, days-off, holidays, terms of contract and working hours. The scheduling process is carried out on a weekly basis, but there are mid-term and long-term conditions and objectives which link each week with the preceding and following weeks. Our package uses firstly a tabu search algorithm to find the best schemes of shifts/days-off to be used to cover the requirements. Secondly, an assignment problem is solved to match the schemes …