Generalized subdifferentials of spectral functions over Euclidean Jordan algebras

  • Bruno F. Lourenço
  • Akiko Takeda
    • Categories Nonlinear Optimization, Nonsmooth Optimization Tags , , , ,

    This paper is devoted to the study of generalized subdifferentials of spectral functions over Euclidean Jordan algebras. Spectral functions appear often in optimization problems playing the role of “regularizer”, “barrier”, “penalty function” and many others. We provide formulae for the regular, approximate and horizon subdifferentials of spectral functions. In addition, under local lower semicontinuity, we … Read more

    Analysis of the BFGS Method with Errors

  • Richard H. Byrd
  • Jorge Nocedal
  • Yuchen Xie
    • Categories Unconstrained Optimization Tags ,

    The classical convergence analysis of quasi-Newton methods assumes that the function and gradients employed at each iteration are exact. In this paper, we consider the case when there are (bounded) errors in both computations and establish conditions under which a slight modification of the BFGS algorithm with an Armijo-Wolfe line search converges to a neighborhood … Read more

    The condition number of a function relative to a set

  • David H. Gutman
  • Javier F. Peña
    • Categories Convex Optimization Tags , , ,

    The condition number of a differentiable convex function, namely the ratio of its smoothness to strong convexity constants, is closely tied to fundamental properties of the function. In particular, the condition number of a quadratic convex function is the square of the aspect ratio of a canonical ellipsoid associated to the function. Furthermore, the condition … Read more

    On Data-Driven Prescriptive Analytics with Side Information: A Regularized Nadaraya-Watson Approach

  • Grani A. Hanasusanto
  • Chin Pang Ho
    • Categories Stochastic Programming

    We consider generic stochastic optimization problems in the presence of side information which enables a more insightful decision. The side information constitutes observable exogenous covariates that alter the conditional probability distribution of the random problem parameters. A decision maker who adapts her decisions according to the observed side information solves an optimization problem where the … Read more

    Fast Robust Methods for Singular State-Space Models

  • Aleksandr Y. Aravkin
  • James V. Burke
  • Sarah Webster
  • Jonathan Jonker
  • Gianluigi Pillonetto
    • Categories Control Applications, Nonsmooth Optimization, Statistics Tags , ,

    State-space models are used in a wide range of time series analysis applications. Kalman filtering and smoothing are work-horse algorithms in these settings. While classic algorithms assume Gaussian errors to simplify estimation, recent advances use a broad range of optimization formulations to allow outlier-robust estimation, as well as constraints to capture prior information. Here we … Read more

    Admissibility of solution estimators for stochastic optimization

  • Amitabh Basu
  • Tu Nguyen
  • Ao Sun
    • Categories Stochastic Programming Tags , , ,

    We look at stochastic optimization problems through the lens of statistical decision theory. In particular, we address admissibility, in the statistical decision theory sense, of the natural sample average estimator for a stochastic optimization problem (which is also known as the empirical risk minimization (ERM) rule in learning literature). It is well known that for … Read more

    Hybrid Rebalancing with Dynamic Hubbing for Free-floating Bike Sharing Using Multi-objective Simulation Optimization

  • Hadi Charkhgard
  • Vahid Mahmoodian
  • Yu Zhang
    • Categories Optimization of Simulated Systems, Transportation Tags , , , ,

    For rebalancing problem of free-floating bike sharing systems, we propose dynamic hubbing (i.e. dynamically determining geofencing areas) and hybrid rebalancing (combining user-based and operator-based strategies) and solve the problem with a novel multi-objective simulation optimization approach. Given historical usage data and real-time bike GPS location information, dynamic geofenced areas (hubs) are determined to encourage users … Read more

    Discrete Approximation Scheme in Distributionally Robust Optimization

  • Yongchao Liu
  • Xiao-Ming Yuan
  • Jin Zhang
    • Categories Robust Optimization Tags , , , ,

    Discrete approximation which is the prevailing scheme in stochastic programming in the past decade has been extended to distributionally robust optimization (DRO) recently. In this paper we conduct rigorous quantitative stability analysis of discrete approximation schemes for DRO, which measures the approximation error in terms of discretization sample size. For the ambiguity set defined through … Read more

    Local Rapid Learning for Integer Programs

  • Timo Berthold
  • Peter J. Stuckey
  • Jakob Witzig
    • Categories Integer Programming Tags , , , ,

    Conflict learning algorithms are an important component of modern MIP and CP solvers. But strong conflict information is typically gained by depth-first search. While this is the natural mode for CP solving, it is not for MIP solving. Rapid Learning is a hybrid CP/MIP approach where CP search is applied at the root to learn … Read more

    A Status Report on Conflict Analysis in Mixed Integer Nonlinear Programming

  • Timo Berthold
  • Stefan Heinz
  • Jakob Witzig
    • Categories (Mixed) Integer Nonlinear Programming Tags , , ,

    Mixed integer nonlinear programs (MINLPs) are arguably among the hardest optimization problems, with a wide range of applications. MINLP solvers that are based on linear relaxations and spatial branching work similar as mixed integer programming (MIP) solvers in the sense that they are based on a branch-and-cut algorithm, enhanced by various heuristics, domain propagation, and … Read more