Month: May 2024

The Service-Centric Vehicle Routing Problem with Crowdshipping

  • Bingjie Zhou
  • Yu Zhang
  • Roberto Baldacci
    • Categories Transportation

    Last-mile delivery services worldwide have embraced crowdshipping, which involves both regular and occasional drivers to reduce transportation costs and potentially ensure timely deliveries. However, real-world uncertainty in travel times leads to delays in deliveries. Motivated by empirical studies on customer impatience with late deliveries, this paper focuses on a service-centric Vehicle Routing Problem with Crowdshipping … Read more

    Lipschitz minimization and the Goldstein modulus

  • Adrian Lewis
    • Categories Nonsmooth Optimization Tags , ,

    Goldstein’s 1977 idealized iteration for minimizing a Lipschitz objective fixes a distance – the step size – and relies on a certain approximate subgradient. That “Goldstein subgradient” is the shortest convex combination of objective gradients at points within that distance of the current iterate. A recent implementable Goldstein-style algorithm allows a remarkable complexity analysis (Zhang … Read more

    Convex optimization on CAT(0) cubical complexes

  • Adrian Lewis
    • Categories Convex Optimization Tags , , , ,

    We consider geodesically convex optimization problems involving distances to a finite set of points A in a CAT(0) cubical complex. Examples include the minimum enclosing ball problem, the weighted mean and median problems, and the feasibility and projection problems for intersecting balls with centers in A. We propose a decomposition approach relying on standard Euclidean … Read more

    A graph-structured distance for heterogeneous datasets with meta variables

  • Edward Hallé-Hannan
  • Charles Audet
  • Youssef Diouane
  • Sébastien Le Digabel
  • Paul Saves
    • Categories Data Science Theory, Optimization in Data Science Tags , , ,

    Heterogeneous datasets emerge in various machine learning or optimization applications that feature different data sources, various data types and complex relationships between variables. In practice, heterogeneous datasets are often partitioned into smaller well-behaved ones that are easier to process. However, some applications involve expensive-to-generate or limited size datasets, which motivates methods based on the whole … Read more

    Freight consolidation through carrier collaboration – A cooperative game

  • Fabio Mercurio
  • Loe Schlicher
  • S.U.K Rohmer
  • Tom Van Woensel
    • Categories Applications - OR and Management Sciences, Game Theory, Transportation Tags , , , ,

    Reducing inefficient truck movements, this research investigates the potential of freight consolidation through carrier collaboration. Considering the financial benefits of consolidation and the additional cost arising from collaboration, we propose a cooperative game to explore under which circumstances carriers can collaborate. We show that stable cost allocations are not always possible, affecting stability and thus … Read more

    Subgradient Convergence Implies Subdifferential Convergence on Weakly Convex Functions: With Uniform Rates Guarantees

  • Feng Ruan
    • Categories Nonsmooth Optimization, Stochastic Programming

    In nonsmooth, nonconvex stochastic optimization, understanding the uniform convergence of subdifferential mappings is crucial for analyzing stationary points of sample average approximations of risk as they approach the population risk. Yet, characterizing this convergence remains a fundamental challenge. This work introduces a novel perspective by connecting the uniform convergence of subdifferential mappings to that of subgradient … Read more

    Optimal Sports League Realignment

  • Nathan Brixius
    • Categories (Mixed) Integer Linear Programming, (Mixed) Integer Nonlinear Programming, Applications - OR and Management Sciences Tags , ,

    We consider approaches for optimally organizing competitive sports leagues in light of competitive and logistical considerations. A common objective is to assign teams to divisions so that intradivisional travel is minimized. We present a bilinear programming formulation based on k-way equipartitioning, and show how this formulation can be extended to account for additional constraints and … Read more

    On the global convergence of a general class of augmented Lagrangian methods

  • Ernesto G. Birgin
  • Gabriel Haeser
  • Nelson Maculan
  • Lennin Mallma Ramirez
    • Categories Constrained Nonlinear Optimization, Nonlinear Optimization Tags , , ,

    In [E. G. Birgin, R. Castillo and J. M. Martínez, Computational Optimization and Applications 31, pp. 31-55, 2005], a general class of safeguarded augmented Lagrangian methods is introduced which includes a large number of different methods from the literature. Besides a numerical comparison including 65 different methods, primal-dual global convergence to a KKT point is … Read more

    Mixed-Integer Linear Optimization for Cardinality-Constrained Random Forests

  • Jan Pablo Burgard
  • Maria Eduarda Pinheiro
  • Martin Schmidt
    • Categories (Mixed) Integer Linear Programming, Optimization in Data Science Tags , , , ,

    Random forests are among the most famous algorithms for solving classification problems, in particular for large-scale data sets. Considering a set of labeled points and several decision trees, the method takes the majority vote to classify a new given point. In some scenarios, however, labels are only accessible for a proper subset of the given … Read more