stochastic optimization

Multistep stochastic mirror descent for risk-averse convex stochastic programs based on extended polyhedral risk measures

  • Vincent Guigues
    • Categories Nonlinear Optimization, Stochastic Programming Tags , , ,

    We consider risk-averse convex stochastic programs expressed in terms of extended polyhedral risk measures. We derive computable confidence intervals on the optimal value of such stochastic programs using the Robust Stochastic Approximation and the Stochastic Mirror Descent (SMD) algorithms. When the objective functions are uniformly convex, we also propose a multistep extension of the Stochastic … Read more

    Nonstationary Direct Policy Search for Risk-Averse Stochastic Optimization

  • Belgacem Bouzaiene-Ayari
  • Somayeh Moazeni
  • Boris Defourny
  • Warren B. Powell
    • Categories Dynamic Programming, Parallel Algorithms, Stochastic Programming Tags , ,

    This paper presents an approach to non-stationary policy search for finite-horizon, discrete-time Markovian decision problems with large state spaces, constrained action sets, and a risk-sensitive optimality criterion. The methodology relies on modeling time variant policy parameters by a non-parametric response surface model for an indirect parametrized policy motivated by the Bellman equation. Through the interpolating … Read more

    The Value of Stochastic Programming in Day-Ahead and Intraday Generation Unit Commitment

  • Kenneth McKinnon
  • Tim Schulze
    • Categories Scheduling, Stochastic Programming Tags , , ,

    The recent expansion of renewable energy supplies has prompted the development of a variety of efficient stochastic optimization models and solution techniques for hydro-thermal scheduling. However, little has been published about the added value of stochastic models over deterministic ones. In the context of day-ahead and intraday unit commitment under wind uncertainty, we compare two-stage … Read more

    An Asynchronous Mini-Batch Algorithm for Regularized Stochastic Optimization

  • Arda Aytekin
  • Hamid Reza Feyzmahdavian
  • Mikael Johansson
    • Categories Convex and Nonsmooth Optimization, Nonlinear Optimization Tags , , , ,

    Mini-batch optimization has proven to be a powerful paradigm for large-scale learning. However, the state of the art parallel mini-batch algorithms assume synchronous operation or cyclic update orders. When worker nodes are heterogeneous (due to different computational capabilities or different communication delays), synchronous and cyclic operations are inefficient since they will leave workers idle waiting … Read more

    Stochastic Optimization using a Trust-Region Method and Random Models

  • Ruobing Chen
  • Matt Menickelly
  • Katya Scheinberg
    • Categories Stochastic Programming, Unconstrained Optimization Tags , , ,

    In this paper, we propose and analyze a trust-region model-based algorithm for solving unconstrained stochastic optimization problems. Our framework utilizes random models of an objective function $f(x)$, obtained from stochastic observations of the function or its gradient. Our method also utilizes estimates of function values to gauge progress that is being made. The convergence analysis … Read more

    From Predictive to Prescriptive Analytics

  • Dimitris Bertsimas
  • Nathan Kallus
    • Categories Applications - OR and Management Sciences Tags , , , , ,

    In this paper, we combine ideas from machine learning (ML) and operations research and management science (OR/MS) in developing a framework, along with specific methods, for using data to prescribe optimal decisions in OR/MS problems. In a departure from other work on data-driven optimization and reflecting our practical experience with the data available in applications … Read more

    Stochastic Quasi-Newton Methods for Nonconvex Stochastic Optimization

  • Wei Liu
  • Shiqian Ma
  • Xiao Wang
    • Categories Nonlinear Optimization, Stochastic Programming Tags , , , , , ,

    In this paper we study stochastic quasi-Newton methods for nonconvex stochastic optimization, where we assume that only stochastic information of the gradients of the objective function is available via a stochastic first-order oracle (SFO). Firstly, we propose a general framework of stochastic quasi-Newton methods for solving nonconvex stochastic optimization. The proposed framework extends the classic … Read more

    Stochastic Compositional Gradient Descent: Algorithms for Minimizing Compositions of Expected-Value Functions

  • Ethan Fang
  • Mengdi Wang
  • Han Liu
    • Categories Convex Optimization, Statistics, Stochastic Programming Tags , , , ,

    Classical stochastic gradient methods are well suited for minimizing expected-value objective functions. However, they do not apply to the minimization of a nonlinear function involving expected values or a composition of two expected-value functions, i.e., problems of the form $\min_x \E_v\[f_v\big(\E_w [g_w(x)]\big) \]$. In order to solve this stochastic composition problem, we propose a class … Read more

    Randomized First-order Methods for Saddle Point Optimization

  • Cong D. Dang
  • Guanghui Lan
    • Categories Convex and Nonsmooth Optimization Tags , , , ,

    In this paper, we present novel randomized algorithms for solving saddle point problems whose dual feasible region is a direct product of many convex sets. Our algorithms can achieve ${\cal O}(1/N)$ rate of convergence by solving only one dual subproblem at each iteration. Our algorithms can also achieve ${\cal O}(1/N^2)$ rate of convergence if a … Read more

    Robust Unit Commitment with Dispatchable Wind: An LP Reformulation of the Second Stage

  • Germán Morales-España
    • Categories Applications - Science and Engineering, Robust Optimization Tags , , ,

    Abstract— The increasing penetration of uncertain generation such as wind and solar in power systems imposes new challenges to the Unit Commitment (UC) problem, one of the most critical tasks in power systems operations. The two most common approaches to address these challenges — stochastic and robust optimization — have drawbacks that prevent or restrict their … Read more