α-Conservative approximation for probabilistically constrained convex programs

  • Authors:
  • Yuichi Takano;Jun-Ya Gotoh

  • Affiliations:
  • Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Ibaraki, Japan 305-8573;Department of Industrial and Systems Engineering, Chuo University, Tokyo, Japan 112-8551

  • Venue:
  • Computational Optimization and Applications
  • Year:
  • 2010

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Abstract

In this paper, we address an approximate solution of a probabilistically constrained convex program (PCCP), where a convex objective function is minimized over solutions satisfying, with a given probability, convex constraints that are parameterized by random variables. In order to approach to a solution, we set forth a conservative approximation problem by introducing a parameter α which indicates an approximate accuracy, and formulate it as a D.C. optimization problem. As an example of the PCCP, the Value-at-Risk (VaR) minimization is considered under the assumption that the support of the probability of the associated random loss is given by a finitely large number of scenarios. It is advantageous in solving the D.C. optimization that the numbers of variables and constraints are independent of the number of scenarios, and a simplicial branch-and-bound algorithm is posed to find a solution of the D.C. optimization. Numerical experiments demonstrate the following: (i) by adjusting a parameter α, the proposed problem can achieve a smaller VaR than the other convex approximation approaches; (ii) when the number of scenarios is large, a typical 0-1 mixed integer formulation for the VaR minimization cannot be solved in a reasonable time and the improvement of the incumbent values is slow, whereas the proposed method can achieve a good solution at an early stage of the algorithm.