Biased Random-key Genetic Algorithms For The Winner Determination Problem In Combinatorial Auctions.

Abstract In this paper, we address the problem of picking a subset of bids in a general combinatorial auction so as to maximize the overall profit using the first-price model. This winner determination problem assumes that a single bidding round is held to determine both the winners and prices to be paid. We introduce six variants of biased random-key genetic algorithms for this problem. Three of them use a novel initialization technique that makes use of solutions of intermediate linear programming relaxations of an exact mixed integer-linear programming model as initial chromosomes of the population. An experimental evaluation compares the effectiveness of the proposed algorithms with the standard mixed linear integer programming formulation, a specialized exact algorithm, and the best-performing heuristics proposed for this problem. The proposed algorithms are competitive and offer strong results, mainly for large-scale auctions.

Modelo de programação quadrática para análise da movimentação logística e comercialização da soja brasileira

The purpose of this work was to analyze the logistical distribution of Brazilian soybean by applying a quadratic programming to a spatial equilibrium model. The soybean transportation system is an important part of the soybean complex in Brazil, since the major part of the costs of this commodity derives from the transportation costs. Therefore, the optimization of this part of the process is essential to a better competitiveness of the Brazilian soybean in the international market. The Brazilian soybean complex have been increasing its agricultural share in the total of the exportation value in the last ten years, but due to other countries' investments the Brazilian exportations cannot be only focused on increasing its production but it still have to be more efficient. This way, a model was reached which can project new frames by switching the transportation costs and conduce the policy makers to new investments in the sector.

Interaction Between Fiscal And Monetary Policy In A Dynamic Nonlinear Model.

The objective of this study is to verify the dynamics between fiscal policy, measured by public debt, and monetary policy, measured by a reaction function of a central bank. Changes in monetary policies due to deviations from their targets always generate fiscal impacts. We examine two policy reaction functions: the first related to inflation targets and the second related to economic growth targets. We find that the condition for stable equilibrium is more restrictive in the first case than in the second. We then apply our simulation model to Brazil and United Kingdom and find that the equilibrium is unstable in the Brazilian case but stable in the UK case.