Environmentally conditioned self-reproduction
Erlang distributed activity times in stochastic activity networks
It is assumed that activity times in stochastic activity networks (SANs) are independent Erlang random variable (r.v.). A recurrence method of determining the th moments of the completion time is presented. Applications are provided for illustration and are used to evaluate the applicability and appropriateness of the Erlang model to represent activity network.
Errata ao artigo "Um algoritmo exacto para o problema da p-mediana" (Port. Math., 42(2) (1983-1984), 151-162)
Experiments with variants of ant algorithms.
A number of extensions of Ant System, the first ant colony optimization (ACO) algorithm, were proposed in the literature. These extensions typically achieve much improved computational results when compared to the original Ant System. However, many design choices of Ant System are left untouched including the fact that solutions are constructed, that real-numbers are used to simulate pheromone trails, and that explicit pheromone evaporation is used. In this article we experimentally investigate...
Generalizations of the standard travelling salesman problem
Genetic algorithm for combinatorial path planning: the subtour problem.
Graph centers used for stabilization of matrix factorizations
Systems of consistent linear equations with symmetric positive semidefinite matrices arise naturally while solving many scientific and engineering problems. In case of a "floating" static structure, the boundary conditions are not sufficient to prevent its rigid body motions. Traditional solvers based on Cholesky decomposition can be adapted to these systems by recognition of zero rows or columns and also by setting up a well conditioned regular submatrix of the problem that...
Hamiltonian problems in edge-colored complete graphs and eulerian cycles in edge-colored graphs : some complexity results
Hamiltonicity and the 3-Opt procedure for the traveling Salesman problem
The 3-Opt procedure deals with interchanging three edges of a tour with three edges not on that tour. For n≥6, the 3-Interchange Graph is a graph on 1/2(n-1)! vertices, corresponding to the hamiltonian tours in K_n; two vertices are adjacent iff the corresponding hamiltonian tours differ in an interchange of 3 edges; i.e. the tours differ in a single 3-Opt step. It is shown that the 3-Interchange Graph is a hamiltonian subgraph of the Symmetric Traveling Salesman Polytope. Upper bounds are derived...
Heuristic and metaheuristic methods for computing graph treewidth
The notion of treewidth is of considerable interest in relation to NP-hard problems. Indeed, several studies have shown that the tree-decomposition method can be used to solve many basic optimization problems in polynomial time when treewidth is bounded, even if, for arbitrary graphs, computing the treewidth is NP-hard. Several papers present heuristics with computational experiments. For many graphs the discrepancy between the heuristic results and the best lower bounds is still very large. The...
Heuristic and metaheuristic methods for computing graph treewidth
The notion of treewidth is of considerable interest in relation to NP-hard problems. Indeed, several studies have shown that the tree-decomposition method can be used to solve many basic optimization problems in polynomial time when treewidth is bounded, even if, for arbitrary graphs, computing the treewidth is NP-hard. Several papers present heuristics with computational experiments. For many graphs the discrepancy between the heuristic results and the best lower bounds is still very large....
Implantation et complexité des techniques de programmation dynamique dans les méthodes de confection de tournées et d'horaires
Improved lower bounds to the travelling salesman problem
Inductive computations on graphs defined by clique-width expressions
Labelling problems for graphs consist in building distributed data structures, making it possible to check a given graph property or to compute a given function, the arguments of which are vertices. For an inductively computable function D, if G is a graph with n vertices and of clique-width at most k, where k is fixed, we can associate with each vertex x of G a piece of information (bit sequence) lab(x) of length O(log2(n)) such that we can compute D in constant time, using only the labels...
Inequality-sum : a global constraint capturing the objective function
This paper introduces a new method to prune the domains of the variables in constrained optimization problems where the objective function is defined by a sum , and where the integer variables are subject to difference constraints of the form . An important application area where such problems occur is deterministic scheduling with the mean flow time as optimality criteria. This new constraint is also more general than a sum constraint defined on a set of ordered variables. Classical approaches...
Inequality-sum: a global constraint capturing the objective function
This paper introduces a new method to prune the domains of the variables in constrained optimization problems where the objective function is defined by a sum y = ∑xi, and where the integer variables xi are subject to difference constraints of the form xj - xi ≤ c. An important application area where such problems occur is deterministic scheduling with the mean flow time as optimality criteria. This new constraint is also more general than a sum constraint defined on a set of ordered variables....
K-class assignments
La recherche de l'ensemble optimal des itinéraires des véhicules dans une entreprise de transports automobiles extra-urbains
La régularisation dans les problèmes combinatoires et son application au problème des tournées de livraison
La régularisation dans les problèmes combinatoires et son application au problème de sectorisation