Symmetry helps: Bounded bi-directional dynamic programming for the elementary shortest path problem with resource constraints

  • Authors:
  • Giovanni Righini;Matteo Salani

  • Affiliations:
  • Dipartimento di Tecnologie dell'Informazione, Universití degli Studi di Milano, via Bramante 65, 26013 Crema, Italy;Dipartimento di Tecnologie dell'Informazione, Universití degli Studi di Milano, via Bramante 65, 26013 Crema, Italy

  • Venue:
  • Discrete Optimization
  • Year:
  • 2006

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Abstract

When vehicle routing problems with additional constraints, such as capacity or time windows, are solved via column generation and branch-and-price, it is common that the pricing subproblem requires the computation of a minimum cost constrained path on a graph with costs on the arcs and prizes on the vertices. A common solution technique for this problem is dynamic programming. In this paper we illustrate how the basic dynamic programming algorithm can be improved by bounded bi-directional search and we experimentally evaluate the effectiveness of the enhancement proposed. We consider as benchmark problems the elementary shortest path problems arising as pricing subproblems in branch-and-price algorithms for the capacitated vehicle routing problem, the vehicle routing problem with distribution and collection and the capacitated vehicle routing problem with time windows.