Global Optimization

Global Optimization of Gas Transportation and Storage: Convex Hull Characterizations and Relaxations

  • Bahar Okumusoglu
  • Burak Kocuk
    • Categories (Mixed) Integer Linear Programming, Energy, Global Optimization Tags , , ,

    Gas transportation and storage has become one of the most relevant and important optimization problems in energy systems. This problem inherently includes highly nonlinear and nonconvex aspects due to gas physics, and discrete aspects due to the control decisions of active network elements. Obtaining even locally optimal solutions for this problem presents significant mathematical and … Read more

    Deterministic global optimization with trained neural networks: Is the envelope of single neurons worth it?

  • Clara Witte
  • Jannik Lüthje
  • Victor Schulte
  • Alexander Mitsos
  • Dominik Bongartz
    • Categories Global Optimization, Global Optimization Applications, Optimization in Data Science Tags , , ,

    Optimization problems containing trained neural networks remain challenging due to their nonconvexity. Deterministic global optimization relies on relaxations which should be tight, quickly convergent, and cheap to evaluate. While envelopes of common activation functions have been established for several years, the envelope of an entire neuron had not. Recently, Carrasco and Mu\~{n}oz (arXiv.2410.23362, 2024) proposed … Read more

    The improvement function in branch-and-bound methods for complete global optimization

  • Stefan Schwarze
  • Oliver Stein
  • Peter Kirst
    • Categories Constrained Nonlinear Optimization, Global Optimization Tags , , , ,

    We present a new spatial branch-and-bound approach for treating optimization problems with nonconvex inequality constraints. It is able to approximate the set of all global minimal points in case of solvability, and else to detect infeasibility. The new technique covers the nonconvex constraints by means of an improvement function which, although nonsmooth, can be treated … Read more

    The improvement function reformulation for graphs of minimal point mappings

  • Stefan Schwarze
  • Oliver Stein
    • Categories Constrained Nonlinear Optimization, Game Theory, Global Optimization Theory Tags , , , , ,

    Graphs of minimal point mappings of parametric optimization problems appear in the definition of feasible sets of bilevel optimization problems and of semi-infinite optimization problems, and the intersection of multiple such graphs defines (generalized) Nash equilibria. This paper shows how minimal point graphs of nonconvex parametric optimization problems can be written with the help of … Read more

    Extending Exact SDP Relaxations of Quadratically Constrained Quadratic Programs

  • Masakazu Kojima
  • Sunyoung Kim
  • Naohiko Arima
    • Categories Convex Optimization, Global Optimization, Semi-definite Programming Tags , , , ,

    The semidefinite (SDP) relaxation of a quadratically constrained quadratic program (QCQP) is called exact if it has a rank-$1$ optimal solution corresponding to a QCQP optimal solution. Given an arbitrary QCQP whose SDP relaxation is exact, this paper investigates incorporating additional quadratic inequality constraints while maintaining the exactness of the SDP relaxation of the resulting … Read more

    New Algorithms for maximizing the difference of convex functions

  • Aharon Ben-Tal
  • Luba Tetruashvili
    • Categories Global Optimization, Global Optimization Applications, Nonlinear Optimization

    Maximizing the difference of 2 convex functions over a convex feasible set (the so called DCA problem) is a hard problem. There is a large number of publications addressing this problem. Many of them are variations of widely used DCA algorithm [20]. The success of this algorithm to reach a good approximation of a global … Read more

    The Least Singular Value Function in Variational Analysis

  • Mario Jelitte
  • Boris S. Mordukhovich
    • Categories Constrained Nonlinear Optimization, Global Optimization Theory, Nonsmooth Optimization Tags , , , ,

    Metric regularity is among the central concepts of nonlinear and variational analysis, constrained optimization, and their numerous applications. However, met- ric regularity can be elusive for some important ill-posed classes of problems includ- ing polynomial equations, parametric variational systems, smooth reformulations of complementarity systems with degenerate solutions, etc. The study of stability issues for such … Read more

    New Sufficient and Necessary Conditions for Constrained and Unconstrained Lipschitzian Error Bounds

  • Andreas Fischer
  • Alexey F. Izmailov
  • Mario Jelitte
    • Categories Complementarity and Variational Inequalities, Global Optimization Theory, Nonsmooth Optimization Tags , , , , , , ,

    Local error bounds play a fundamental role in mathematical programming and variational analysis. They are used e.g. as constraint qualifications in optimization, in developing calculus rules for generalized derivatives in nonsmooth and set-valued analysis, and they serve as a key ingredient in the design and convergence analysis of Newton-type methods for solving systems of possibly … Read more

    On Sum-Rules for Second-Order Contingent Derivatives

  • Mario Jelitte
    • Categories Constrained Nonlinear Optimization, Global Optimization Theory, Nonsmooth Optimization Tags , , ,

    We are concerned with contingent derivatives and their second-order counterparts (introduced by Ngai et al.) of set-valued mappings. Special attention is given to the development of new sum-rules for second-order contingent derivatives. To be precise, we want to find conditions under which the second-order contingent derivative of the sum of a smooth and a set-valued … Read more

    Constructing QCQP Instances Equivalent to Their SDP Relaxations

  • Masakazu Kojima
  • Naohiko Arima
  • Sunyoung Kim
    • Categories Global Optimization Applications, Quadratic Programming, Semi-definite Programming Tags , ,

    General quadratically constrained quadratic programs (QCQPs) are challenging to solve as they are known to be NP-hard. A popular approach to approximating QCQP solutions is to use semidefinite programming (SDP) relaxations. It is well-known that the optimal value η of the SDP relaxation problem bounds the optimal value ζ  of the QCQP from below, i.e., … Read more