Ricardo Fukasawa

Optimal counterfactual explanations for k-Nearest Neighbors using Mathematical Optimization and Constraint Programming

  • Thibaut Vidal
  • Ricardo Fukasawa
  • Louis-Martin Rousseau
  • Claudio Contardo
    • Categories Applications - Science and Engineering, Data Science Algorithms Tags , , , ,

    \(\) Within the topic of explainable AI, counterfactual explanations to classifiers have received significant recent attention. We study counterfactual explanations that try to explain why a data point received an undesirable classification by providing the closest data point that would have received a desirable one. Within the context of one the simplest and most popular … Read more

    Hardness of pricing routes for two-stage stochastic vehicle routing problems with scenarios

  • Matheus Jun Ota
  • Ricardo Fukasawa
    • Categories Combinatorial Optimization, Integer Programming, Stochastic Programming Tags , ,

    The vehicle routing problem with stochastic demands (VRPSD) generalizes the classic vehicle routing problem by considering customer demands as random variables. Similarly to other vehicle routing variants, state-of-the-art algorithms for the VRPSD are often based on set-partitioning formulations, which require efficient routines for the associated pricing problems. However, all these set-partitioning-based approaches have strong assumptions … Read more

    A comparison of different approaches for the vehicle routing problem with stochastic demands

  • Matheus Jun Ota
  • Ricardo Fukasawa
    • Categories Branch and Cut Algorithms, Production and Logistics, Stochastic Programming Tags , ,

    The vehicle routing problem with stochastic demands (VRPSD) is a well studied variant of the classic (deterministic) capacitated vehicle routing problem (CVRP) where the customer demands are given by random variables. Two prominent approaches for solving the VRPSD model it either as a chance-constraint program (CC-VRPSD) or as a two-stage stochastic program (2S-VRPSD). In this … Read more

    A Fast Combinatorial Algorithm for the Bilevel Knapsack Problem with Interdiction Constraints

  • Noah Weninger
  • Ricardo Fukasawa
    • Categories Combinatorial Optimization, Dynamic Programming Tags , , , ,

    \(\) We consider the bilevel knapsack problem with interdiction constraints, a fundamental bilevel integer programming problem which generalizes the 0-1 knapsack problem. In this problem, there are two knapsacks and \(n\) items. The objective is to select some items to pack into the first knapsack such that the maximum profit attainable from packing some of … Read more

    The complexity of branch-and-price algorithms for the capacitated vehicle routing problem with stochastic demands

  • Ricardo Fukasawa
    • Categories Combinatorial Optimization, Integer Programming, Stochastic Programming Tags , ,

    The capacitated vehicle routing problem with stochastic demands (CVRPSD) is a variant of the deterministic capacitated vehicle routing problem where customer demands are random variables. While the most successful formulations for several deterministic vehicle-routing problem variants are based on a set-partitioning formulation, adapting such formulations for the CVRPSD under mild assumptions on the demands remains … Read more

    The Arc-Item-Load and Related Formulations for the Cumulative Vehicle Routing Problem

  • Mauro Henrique Mulati
  • Ricardo Fukasawa
  • Flávio Keidi Miyazawa
    • Categories (Mixed) Integer Linear Programming, Combinatorial Optimization Tags , , , ,

    The Capacitated Vehicle Routing Problem (CVRP) consists of finding the cheapest way to serve a set of customers with a fleet of vehicles of a given capacity. While serving a particular customer, each vehicle picks up its demand and carries its weight throughout the rest of its route. While costs in the classical CVRP are … Read more

    Multi-Row Intersection Cuts based on the Infinity Norm

  • Ricardo Fukasawa
  • Laurent Poirrier
  • Alinson S. Xavier
    • Categories (Mixed) Integer Linear Programming Tags , ,

    When generating multi-row intersection cuts for Mixed-Integer Linear Optimization problems, an important practical question is deciding which intersection cuts to use. Even when restricted to cuts that are facet-defining for the corner relaxation, the number of potential candidates is still very large, specially for instances of large size. In this paper, we introduce a subset … Read more

    Split cuts from sparse disjunctions

  • Ricardo Fukasawa
  • Laurent Poirrier
  • Shenghao Yang
    • Categories (Mixed) Integer Linear Programming, Cutting Plane Approaches Tags , , ,

    Split cuts are arguably the most effective class of cutting planes within a branch-and-cut framework for solving general Mixed-Integer Programs (MIP). Sparsity, on the other hand, is a common characteristic of MIP problems, and it is an important part of why the simplex method works so well inside branch-and-cut. In this work, we evaluate the … Read more

    Permutations in the factorization of simplex bases

  • Ricardo Fukasawa
  • Laurent Poirrier
    • Categories Linear Programming Tags , ,

    The basis matrices corresponding to consecutive iterations of the simplex method only differ in a single column. This fact is commonly exploited in current LP solvers to avoid having to compute a new factorization of the basis at every iteration. Instead, a previous factorization is updated to reflect the modified column. Several methods are known … Read more

    The (not so) Trivial Lifting in Two Dimensions

  • Ricardo Fukasawa
  • Laurent Poirrier
  • Alinson S. Xavier
    • Categories (Mixed) Integer Linear Programming Tags ,

    When generating cutting-planes for mixed-integer programs from multiple rows of the simplex tableau, the usual approach has been to relax the integrality of the non-basic variables, compute an intersection cut, then strengthen the cut coefficients corresponding to integral non-basic variables using the so-called trivial lifting procedure. Although of polynomial-time complexity in theory, this lifting procedure … Read more