Perspective Envelopes for Bilinear Functions
Given the bilinear function f(x,y) = xy, and the constraint x
A polynomial-time descent method for separable convex optimization problems with linear constraints
We propose a polynomial algorithm for a separable convex optimization problem with linear constraints. We do not make any additional assumptions about the structure of the objective function except for polynomial computability. That is, the objective function can be non-differentiable. The running time of our algorithm is polynomial in the the size of the input … Read more
Machine Learning to Balance the Load in Parallel Branch-and-Bound
We describe in this paper a new approach to parallelize branch-and-bound on a certain number of processors. We propose to split the optimization of the original problem into the optimization of several subproblems that can be optimized separately with the goal that the amount of work that each processor carries out is balanced between the … Read more
Projected Reflected Gradient Methods for Monotone Variational Inequalities
This paper is concerned with some new projection methods for solving variational inequality problems with monotone and Lipschitz-continuous mapping in Hilbert space. First, we propose the projected reflected gradient algorithm with a constant stepsize. It is similar to the projected gradient method, namely, the method requires only one projection onto the feasible set and only … Read more
A Multi-Layer Line Search Method to Improve the Initialization of Optimization Algorithms
We introduce a novel metaheuristic methodology to improve the initialization of a given deterministic or stochastic optimization algorithm. Our objective is to improve the performance of the considered algorithm, called core optimization algorithm, by reducing its number of cost function evaluations, by increasing its success rate and by boosting the precision of its results. In … Read more
An ILP-based local search procedure for the VRP with pickups and deliveries
In this paper we address the Vehicle Routing Problem with Pickups and Deliveries (VRPPD), an extension of the classical Vehicle Routing Problem (VRP) where we consider precedences among customers, and develop an Integer Linear Programming (ILP) based local search procedure. We consider the capacitated one-to-one variant, where a particular precedence must be satisfied between pairs … Read more
A cluster-first route-second approach for the Swap Body Vehicle Routing Problem
The Swap Body Vehicle Routing Problem (SB-VRP) is a generalization of the classical Vehicle Routing Problem (VRP) where a particular structure as well as several operational aspects for the trucks composing the fleet are considered. This research has been motivated by the VeRoLog Solver Challenge 2014, organized together by VeRoLog and PTV group, aiming to … Read more
Convex Hull Pricing in Electricity Markets: Formulation, Analysis, and Implementation Challenges
Recent widespread interest in Convex Hull Pricing has not been accompanied by an equally broad understanding of the method. This paper seeks to narrow the gap between enthusiasm and comprehension. The connection between Convex Hull Pricing and basic electricity market clearing processes is clearly developed, and a new formulation of the pricing problem is presented. … Read more
A Nonmonotone Approach without Differentiability Test for Gradient Sampling Methods
Recently, optimization problems involving nonsmooth and locally Lipschitz functions have been subject of investigation, and an innovative method known as Gradient Sampling has gained attention. Although the method has shown good results for important real problems, some drawbacks still remain unexplored. This study suggests modifications to the gradient sampling class of methods in order to … Read more
The One-Dimensional Dynamic Dispatch Waves Problem
We study same-day delivery (SDD) distribution systems by formulating the Dynamic Dispatch Wave Problem (DDWP), which models a depot where delivery requests arrive dynamically throughout a service day. At any dispatch epoch (wave), the information available to the decision maker is (1) a set of known, open requests which remain unfulfilled, and (2) a set … Read more