Previously scheduled production plans frequently need to be updated because of demand uncertainty. After making a comprehensive de"nition of nervousness which includes costs for changes in production schedule and quantity, we suggest three methodologies. Two methods are modi"ed versions of very well-known methods: the Wagner}Whitin algorithm and the Silver}Meal heuristic. However, our de"nition...

We study a family of unbounded polyhedra arising in the study of uncapacitated lot-sizing problems with Wagner-Whitin costs. With n the number of periods, we completely characterize the bounded faces of maximal dimension, and derive an O(n) algorithm to express any point within the polyhedron as a convex combination of extreme points and extreme rays. We also study adjacency on the polyhedra, a...

We consider the single item lot-sizing problem with capacities that are non-decreasing over time. When the cost function is i) non-speculative or Wagner-Whitin (for instance, constant unit production costs and non-negative unit holding costs), and ii) the production set-up costs are non-increasing over time, it is known that the minimum cost lotsizing problem is polynomially solvable using dyna...

We consider the single-item discrete lot-sizing and scheduling problem. We present a partial linear description of the convex hull of feasible solutions that solves this problem in the presence of Wagner-Whitin costs.

Loss of customer goodwill in uncapacitated single level lot-sizing is studied with a mixed integer programming model extending the well-known Wagner-Whitin (WW) model. The objective is to maximize profit from production and sales of a single good over a finite planning horizon. Demand, costs, and prices vary with time. Unsatisfied demand cannot be backordered. It leads to the immediate loss of ...

This paper derives the impacts of early order commitments on the performance of many inventory policies used by retailers in a supply chain. Model parameters and operating conditions are emulated from a local business, supplying a standard product to its retailers. The purpose of this research work is to justify the two renowned heuristic models (Wagner Whitin algorithm and Silver–Meal heuristi...

We investigate the dynamic lot-size problem under stochastic and non-stationary demand over the planning horizon. The problem is tackled by using three popular heuristic methods from the fields of evolutionary computation and swarm intelligence, namely particle swarm optimization, differential evolution and harmony search. To the best of the authors’ knowledge, this is the first investigation o...