A proximal subgradient projection algorithm for linearly constrained strictly convex problems

  • Authors:
  • Adam Ouorou

  • Affiliations:
  • France Telecom R&D, France

  • Venue:
  • Optimization Methods & Software
  • Year:
  • 2007

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Abstract

We propose a new algorithm for linearly constrained strictly convex problems. This algorithm follows the characterization of saddle points introduced earlier in ref. [Ouorou, A., 2000, A primal-dual algorithm for monotropic programming and its application to network optimization. Computational Optimization and Applications, 15(2), 125-143.], using two different augmented Lagrangian functions defined for the primal problem and its dual. The saddle points may be computed in a variety of ways. We propose a scheme that results in a special implementation of Martinet's proximal algorithm ref. [Martinet, B. 1970, Régularisation d'inéquations variationnelles par approximations successives. Revue Franç'Informatique et de Recherche Opérationnelle, 3, 154-179.]. In the primal space, the resulting algorithm appears as a nonsmooth version of the projection algorithm by Rosen ref. [Rosen, J.B., 1960, The gradient projected method for nonlinear programming, part I: Linear Constraints. Journal of the Society for Industrial and Applied Mathematics, 8, 181-217.]. The dual iterates are generated through an unconstrained subproblem which can be solved efficiently by L-BFGS refs. [Byrd, R., Lu, P., Nocedal, J. and Zhu, C. 1995, A limited memory algorithm for bound constrained optimization. SIAM Journal on Scientific Computation, 16(5), 1190-1208.; Liu, D. and Nocedal, J., 1989, On the limited memory BFGS method for large scale optimization. Mathematical Programming B 45, 503-528.]. We establish convergence with no use of the concept of resolvent of maximal monotone operators. To assess the numerical behaviour of the algorithm, we use some randomly generated quadratic network flow problems and compare it with PPRN, a specialized code for linear and nonlinear cost network flow problems.