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M. El Maghri

Publications and source records attributed to M. El Maghri.

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Generalized Reduced Jacobian Method

In a recent work, we presented the reduced Jacobian method (RJM) as an extension of Wolfe's reduced gradient method to multicriteria (multiobjective) optimization problems dealing with linear constraints. This approach reveals that using a reduction technique of the Jacobian matrix of the objective avoids scalarization. In the present work, we intend to generalize RJM to handle nonlinear constraints too. In fact, we propose a generalized reduced Jacobian (GRJ) method that extends Abadie-Carpentier's approach for single-objective programs. To this end, we adopt a global reduction strategy based on the fundamental theorem of implicit functions. In this perspective, only a reduced descent direction common to all the criteria is computed by solving a simple convex program. After establishing an Armijo-type line search condition that ensures feasibility, the resulting algorithm is shown to be globally convergent, under mild assumptions, to a Pareto critical (KKT-stationary) point. Finally, experimental results are presented, including comparisons with other deterministic and evolutionary approaches.

math.OC

${\varepsilon}$-optimality in reverse convex optimization

We characterize approximate global optimal solutions (${\varepsilon}$-optima) to reverse optimization problems, namely, problems whose non-convex constraint is of the form $h(x) \geq 0$. This issue has not been addressed previously in the literature. Our idea consists of converting the reverse program into an unconstrained bicriteria DC program. The main condition presented is obtained in terms of Fenchel's ${\varepsilon}$-subdifferentials thanks to an earlier result in difference vector optimization by El Maghri. This extends and improves similar results from the literature dealing with exact (${\varepsilon} = 0$) solutions. Moreover, as we consider functions with extended values, our approach also applies to reverse problems subject to additional convex constraints, provided that Moreau-Rockafellar or Attouch-Brézis constraint qualification conditions are satisfied. Similarly, new results for the special case of a nonlinear equality constraint $h(x) = 0$ are also obtained.

math.OC