Philippe L. Toint

A trust-funnel method for nonlinear optimization problems with general nonlinear constraints and its application to derivative-free optimization

  • Phillipe Sampaio
  • Philippe L. Toint
    • Categories Constrained Nonlinear Optimization Tags , , ,

    A trust-funnel method is proposed for solving nonlinear optimization problems with general nonlinear constraints. It extends the one presented by Gould and Toint (Math. Prog., 122(1):155-196, 2010), originally proposed for equality-constrained optimization problems only, to problems with both equality and inequality constraints and where simple bounds are also considered. As the original one, our method … Read more

    Corrigendum: On the complexity of finding first-order critical points in constrained nonlinear optimization

  • Coralia Cartis
  • Nicholas I. M. Gould
  • Philippe L. Toint
    • Categories Constrained Nonlinear Optimization Tags , ,

    In a recent paper (Cartis, Gould and Toint, Math. Prog. A 144(1-2) 93–106, 2014), the evaluation complexity of an algorithm to find an approximate first-order critical point for the general smooth constrained optimization problem was examined. Unfortunately, the proof of Lemma 3.5 in that paper uses a result from an earlier paper in an incorrect … Read more

    Worst-case evaluation complexity of regularization methods for smooth unconstrained optimization using Hölder continuous gradients

  • Coralia Cartis
  • Nicholas I. M. Gould
  • Philippe L. Toint
    • Categories Unconstrained Optimization Tags , ,

    The worst-case behaviour of a general class of regularization algorithms is considered in the case where only objective function values and associated gradient vectors are evaluated. Upper bounds are derived on the number of such evaluations that are needed for the algorithm to produce an approximate first-order critical point whose accuracy is within a user-defined … Read more

    Simple examples for the failure of Newton’s method with line search for strictly convex minimization

  • Florian Jarre
  • Philippe L. Toint
    • Categories Unconstrained Optimization Tags ,

    In this paper two simple examples of a twice continuously differentiable strictly convex function $f$ are presented for which Newton’s method with line search converges to a point where the gradient of $f$ is not zero. The first example uses a line search based on the Wolfe conditions. For the second example, some strictly convex … Read more

    A derivative-free trust-funnel method for equality-constrained nonlinear optimization

  • Phillipe Sampaio
  • Philippe L. Toint
    • Categories Constrained Nonlinear Optimization Tags , , , ,

    In this work, we look into new derivative-free methods to solve equality-constrained optimization problems. Of particular interest, are the trust-region techniques, which have been investigated for the unconstrained and bound-constrained cases. For solving equality-constrained optimization problems, we introduce a derivative-free adaptation of the trust-funnel method combined with a self-correcting geometry scheme and present some encouraging … Read more

    An Interior-Point Trust-Funnel Algorithm for Nonlinear Optimization

  • Frank E. Curtis
  • Nicholas I. M. Gould
  • Daniel P. Robinson
  • Philippe L. Toint
    • Categories Constrained Nonlinear Optimization, Nonlinear Optimization Tags , , , , , ,

    We present an interior-point trust-funnel algorithm for solving large-scale nonlinear optimization problems. The method is based on an approach proposed by Gould and Toint (Math Prog 122(1):155–196, 2010) that focused on solving equality constrained problems. Our method is similar in that it achieves global convergence guarantees by combining a trust-region methodology with a funnel mechanism, … Read more

    Quasi-Newton updates with weighted secant equations

  • Serge Gratton
  • Vincent Malmedy
  • Philippe L. Toint
    • Categories Nonlinear Systems and Least-Squares, Unconstrained Optimization Tags , ,

    We provide a formula for variational quasi-Newton updates with multiple weighted secant equations. The derivation of the formula leads to a Sylvester equation in the correction matrix. Examples are given. Citation Report naXys-09-2013, Namur Centre for Complex Systems, Unibersity of Namur, Namur (Belgium) Article Download View Quasi-Newton updates with weighted secant equations

    Adaptive Observations And Multilevel Optimization In Data Assimilation

  • Serge Gratton
  • Monserrat Rincon-Camacho
  • Philippe L. Toint
    • Categories Nonlinear Systems and Least-Squares, Optimization of Systems modeled by PDEs Tags , ,

    We propose to use a decomposition of large-scale incremental four dimensional (4D-Var) data assimilation problems in order to make their numerical solution more efficient. This decomposition is based on exploiting an adaptive hierarchy of the observations. Starting with a low-cardinality set and the solution of its corresponding optimization problem, observations are adaptively added based on … Read more

    An example of slow convergence for Newton’s method on a function with globally Lipschitz continuous Hessian

  • Coralia Cartis
  • Nicholas I. M. Gould
  • Philippe L. Toint
    • Categories Nonlinear Systems and Least-Squares, Unconstrained Optimization Tags ,

    An example is presented where Newton’s method for unconstrained minimization is applied to find an $\epsilon$-approximate first-order critical point of a smooth function and takes a multiple of $\epsilon^{-2}$ iterations and function evaluations to terminate, which is as many as the steepest-descent method in its worst-case. The novel feature of the proposed example is that … Read more

    CUTEst: a Constrained and Unconstrained Testing Environment with safe threads

  • Nicholas I. M. Gould
  • Dominique Orban
  • Philippe L. Toint
    • Categories Optimization Software and Modeling Systems Tags ,

    We describe the most recent evolution of our constrained and unconstrained testing environment and its accompanying SIF decoder. Code-named SIFDecode and CUTEst, these updated versions feature dynamic memory allocation, a modern thread-safe Fortran modular design, a new Matlab interface and a revised installation procedure integrated with GALAHAD. Citation Technical Report Rutherford Appleton Laboratory Chilton, Oxfordshire, … Read more