Month: December 2013

Equivalence and Strong Equivalence between Sparsest and Least l1-Norm Nonnegative Solutions of Linear Systems and Their Application

  • Yun-Bin Zhao
    • Categories Convex Optimization, Global Optimization, Linear Programming Tags , , , ,

    Many practical problems can be formulated as $\ell_0$-minimization problems with nonnegativity constraints, which seek the sparsest nonnegative solutions to underdetermined linear systems. Recent study indicates that $\ell_1$-minimization is efficient for solving some classes of $\ell_0$-minimization problems. From a mathematical point of view, however, the understanding of the relationship between $\ell_0$- and $\ell_1$-minimization remains incomplete. In … Read more

    On local convergence of the method of alternating projections

  • Dominikus Noll
  • Aude Rondepierre
    • Categories Convex and Nonsmooth Optimization Tags , , , , , ,

    The method of alternating projections is a classical tool to solve feasibility problems. Here we prove local convergence of alternating projections between subanalytic sets A,B under a mild regularity hypothesis on one of the sets. We show that the speed of convergence is O$(k^{-\rho})$ for some $\rho\in(0,\infty)$. Citation Université de Toulouse, Institut de Mathématiques, december … Read more

    Equivalence and Strong Equivalence between Sparsest and Least $\ell_1hBcNorm Nonnegative Solutions of Linear Systems and Their Application

  • Yun-Bin Zhao
    • Categories Applications - Science and Engineering, Convex Optimization, Linear Programming Tags , , , ,

    Many practical problems can be formulated as $\ell_0$-minimization problems with nonnegativity constraints, which seek the sparsest nonnegative solutions to underdetermined linear systems. Recent study indicates that $\ell_1$-minimization is efficient for solving some classes of $\ell_0$-minimization problems. From a mathematical point of view, however, the understanding of the relationship between $\ell_0$- and $\ell_1$-minimization remains incomplete. In … Read more

    Uniqueness Conditions for A Class of $\ell_0hBcMinimization Problems

  • C Xu
  • Yun-Bin Zhao
    • Categories Applications - OR and Management Sciences, Applications - Science and Engineering, Data-Mining Tags ,

    We consider a class of $\ell_0$-minimization problems, which is to search for the partial sparsest solution to an underdetermined linear system with additional constraints. We introduce several concepts, including $l_p$-induced quasi-norm ($0

    Worst-Case Performance Analysis of Some Approximation Algorithms for Minimizing Makespan and Flow-Time

  • Michael Huang
  • Peruvemba Sundaram Ravi
  • Levent Tunçel
    • Categories Approximation Algorithms, Scheduling Tags , , ,

    In 1976, Coffman and Sethi conjectured that a natural extension of LPT list scheduling to the bicriteria scheduling problem of minimizing makespan over flowtime optimal schedules, called LD algorithm, has a simple worst-case performance bound: (5m-2)/(4m-1) , where m is the number of machines. We study structure of potential minimal counterexamples to this conjecture and … Read more

    An Improvised Approach to Robustness in Linear Optimization

  • Mehdi Karimi
  • Somayeh Moazeni
  • Levent Tunçel
    • Categories Applications - OR and Management Sciences, Robust Optimization Tags ,

    We treat uncertain linear programming problems by utilizing the notion of weighted analytic centers and notions from the area of multi-criteria decision making. In addition to many practical advantages, due to the flexibility of our approach, we are able to prove that the robust optimal solutions generated by our algorithms are at least as desirable … Read more

    Preconditioning issues in the numerical solution of nonlinear equations and nonlinear least squares

  • Stefania Bellavia
  • Margherita Porcelli
    • Categories Nonlinear Optimization Tags , ,

    Second order methods for optimization call for the solution of sequences of linear systems. In this survey we will discuss several issues related to the preconditioning of such sequences. Covered topics include both techniques for building updates of factorized preconditioners and quasi-Newton approaches. Sequences of unsymmetric linear systems arising in Newton- Krylov methods will be … Read more

    A Relaxed-Projection Splitting Algorithm for Variational Inequalities in Hilbert Spaces

  • Yunier Bello-Cruz
  • R. Diaz Millan
    • Categories Complementarity and Variational Inequalities, Nonlinear Optimization, Nonsmooth Optimization Tags , , , , ,

    We introduce a relaxed-projection splitting algorithm for solving variational inequalities in Hilbert spaces for the sum of nonsmooth maximal monotone operators, where the feasible set is defined by a nonlinear and nonsmooth continuous convex function inequality. In our scheme, the orthogonal projections onto the feasible set are replaced by projections onto separating hyperplanes. Furthermore, each … Read more

    The inexact projected gradient method for quasiconvex vector optimization problems

  • Yunier Bello-Cruz
  • Glaydston Bento
  • Gemayqzel Bouza
  • R.F.B. Costa
    • Categories Generalized Convexity/Monoticity, Multi-Criteria Optimization, Nonlinear Optimization

    Vector optimization problems are a generalization of multiobjective optimization in which the preference order is related to an arbitrary closed and convex cone, rather than the nonnegative octant. Due to its real life applications, it is important to have practical solution approaches for computing. In this work, we consider the inexact projected gradient-like method for … Read more