A polynomial time algorithm for makespan minimization on one machine with forbidden start and completion times

International audienceWe consider the problem of scheduling independent jobs on a single resource under a special unavailability constraint: a set of forbidden instants is given, where no job is allowed to start or complete. We show that a schedule without idle time always exists if the number of forbidden instants is less than the number of distinct processing times appearing in the instance. We derive quite a fast algorithm to find such a schedule, based on an hybridization between a list algorithm and local exchange. As a corollary minimizing the makespan for a fixed number of forbidden instants is polynomia

Cyclic production in regular robotic cells: A counterexample to the 1-cycle conjecture

Robotic cells consist in a flow-shop where transportation of the parts between machines is handled by a robot. We consider cyclic production of identical parts and optimization of the cell's throughput. Production cycle of 1 part are easier to describe implement and there is a conjecture about their dominance. This conjecture has been studied for linear layout cells, for which the 1-cycles are well known, but not for cells with circular layout, where the input and output buffers are at the same position. We provide a counterexample to the conjecture for this case

Good Production Cycles for Circular Robotic Cells

In this paper, we study cyclic production for throughput optimization in robotic flow-shops. We are focusing on simple production cycles. Robotic cells can have a linear or a circular layout: most classical results on linear cells cannot be extended to circular cells, making it difficult to quantify the potential gain brought by the latter configuration. Moreover, though the problem of finding the best one part production cycle is polynomial for linear cells, it is NP-hard for circular cells. We consider the special case of circular balanced cells. We first consider three basic production cycles, and focus on one which is specific to circular cells, for which we establish the expression of the cycle time. Then, we provide a counterexample to a classical conjecture still open in this configuration. Finally, based on computational experiments, we make a conjecture on the dominance of a family of cycle, which could lead to a polynomial algorithm for finding the best 1-cycle for circular balanced cells

LAD models, trees and an analog of the fundamental theorem of arithmetic

International audienceMotivated by applications of Logical Analysis Data (LAD) in medical contexts, original discrete optimization problems are proposed. When a patient arrives with a presumption of a disease, he is submitted to a sequence of tests. From one patient to another, the tests allowing to detect the disease may vary. A subset of tests whose results detect the disease in a given part of the population is called a pattern, which has its own prevalence in the population. If there is only a limited number of tests that can be done, which ones must be selected in order to maximize the number of spotted patients ? Or, if each test has a cost, in which order the tests have to be done, in order to minimize the cost ? It is the kind of questions that are investigated in this paper. For various special cases, polynomial algorithms are proposed, especially when the hypergraph whose vertices are the tests and whose edges are the patterns is a tree graph. One of these questions involves a criterion which is not a number but a sequence of numbers. The objective is then to find the best sequence for the lexicographic order. To solve this question, a new product on finite sequences is defined, namely the maximum shuffle product, which maps two sequences to their shuffle that is maximal for the lexicographic order. Surprisingly, this product leads to a theorem similar to the fundamental theorem of arithmetic: every sequence can be written uniquely as the product of prime sequences, with the suitable definition of prime sequences

Caractérisation des instances difficiles de problèmes d'optimisation NP-difficiles

L'étude expérimentale d'algorithmes est un sujet crucial dans la conception de nouveaux algorithmes, puisque le contexte d'évaluation influence inévitablement la mesure de la qualité des algorithmes. Le sujet particulier qui nous intéresse dans l'étude expérimentale est la pertinence des instances choisies pour servir de base de test à l'expérimentation. Nous formalisons ce critère par la notion de "difficulté d'instance" qui dépend des performances pratiques de méthodes de résolution. Le coeur de la thèse porte sur un outil pour évaluer empiriquement la difficulté d'instance. L'approche proposée présente une méthode de benchmarking d'instances sur des jeux de test d'algorithmes. Nous illustrons cette méthode expérimentale pour évaluer des classes d'instances à travers plusieurs exemples d'applications sur le problème du voyageur de commerce. Nous présentons ensuite une approche pour générer des instances difficiles. Elle repose sur des opérations qui modifient les instances, mais qui permettent de retrouver facilement une solution optimale, d'une instance à l'autre. Nous étudions théoriquement et expérimentalement son impact sur les performances de méthodes de résolution.The empirical study of algorithms is a crucial topic in the design of new algorithms because the context of evaluation inevitably influences the measure of the quality of algorithms. In this topic, we particularly focus on the relevance of instances forming testbeds. We formalize this criterion with the notion of 'instance hardness' that depends on practical performance of some resolution methods. The aim of the thesis is to introduce a tool to evaluate instance hardness. The approach uses benchmarking of instances against a testbed of algorithms. We illustrate our experimental methodology to evaluate instance classes through several applications to the traveling salesman problem. We also suggest possibilities to generate hard instances. They rely on operations that modify instances but that allow to easily find the optimal solution of one instance from the other. We theoretically and empirically study their impact on the performance of some resolution methods.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

A influência de um programa de iniciação esportiva no desempenho motor e na rotina de atividades de crianças

As oportunidades disponibilizadas para criança em diferentes contextos de desenvolvimento possuem papel fundamental no desfecho motor bem como nos hábitos de vida da criança. Uma base motora diversificada é importante para que a criança possa se inserir com sucesso em atividades esportivas ao longo da adolescência. O objetivo deste estudo foi investigar o efeito da inserção de um programa de iniciação esportiva sobre o desempenho motor e na rotina de atividades infantis. O Test of Gross Motor Development-Second Edition e um questionário adaptado sobre rotina de atividades na infância foram utilizados no presente estudo. As crianças foram pareadas e distribuídas em grupos controle e interventivo. O grupo interventivo participou de um programa de iniciação esportiva, com duração de 35 semanas e 56 dias de aulas. As crianças do grupo interventivo frequentavam o programa duas vezes por semana e as aulas eram implementadas com o clima de motivação para a maestria. As crianças do grupo controle participaram de aulas regulares de educação física duas vezes por semana. Os resultados indicaram: (1)mudanças positivas e significativas do pré- para o pós-intervenção no quociente motor, nas habilidades locomotoras e de controle de objeto no grupo de crianças que participou no programa de intervenção; (2) escores motores superiores no pós-teste para o grupo interventivo; (3) mudanças positivas na rotina de atividade diárias do grupo interventivo; e (4) mudanças negativas na rotina de atividade diárias no grupo controle. A participação em programas esportivos resulta em aumento da proficiência motora e rotinas mais voltadas para o movimento em crianças

A Branch-and-Price Algorithm for Scheduling Observations on a Telescope

International audienceWe address a parallel machine scheduling problem for which the objective is to maximize the weighted number of scheduled tasks, and with the special constraint that each task has a mandatory processing instant. This problem arises, in our case, to schedule a set of astronomical observations on a telescope. We prove that the problem is NP-complete, and we propose a constraint- programming-based branch-and-price algorithm to solve it. Experiments on real and realistic datasets show that the method provides optimal solutions very efficiently

The maximum deviation just-in-time scheduling problem

This note revisits the maximum deviation just-in-time (MDJIT) scheduling problem previously investigated by Steiner and Yeomans. Its main result is a set of algebraic necessary and sufficient conditions for the existence of a MDJIT schedule with a given objective function value. These conditions are used to provide a finer analysis of the complexity of the MDJIT problem. The note also investigates various special cases of the MDJIT problem and suggests several questions for further investigation. (C) 2003 Elsevier B.V. All rights reserved

Intégrer les questions environnementales dans les cours de RO

International audienceL'objectif de cette présentation est de réfléchir à comment construire ensemble un imaginaire en lien avec les questions environnementales et sociétales dans des cours de Recherche Opérationnelle. Nous proposons de construire une base d'exercices sur ces thèmes qui soient utiles à l'apprentissage des outils de RO, qui puissent être partagés, qui permettent une réflexion riche au delà du cours de RO et qui puissent montrer une démarche scientifique dans l'étude de ces problèmes. Une première tentative de base d'exercices collaborative est proposée ici :https://moodle.caseine.org/mod/page/view.php?id=4656

Identical part production in cyclic robotic cells: a state of the art

This document gives a state of the art on cyclic scheduling of identical parts in robotic cells. It describes classical configurations of robotic cells and introduces basic concepts and tools for dealing with cyclic productions. Then it describes the known results for the classical case where the parts can remain on the machine waiting for the robot and for the no-wait case where the parts have to be removed from the machine as soon as their processing is finished. A detailed list of open questions is also give