Abstract. The Graphical Traveling Salesman Polyhedron (GTSP) has been proposed by Naddef and Rinaldi to be viewed as a relaxation of the Symmetric Traveling Salesman Polytope (STSP). It has also been employed by Applegate, Bixby, Chvátal, and Cook for solving the latter to optimality by the Branch-and-Cut method. There is a close natural connection between the two polyhedra. Until now, it was n...

Given a graph with n nodes each of them having labels equal either to 1 or 2 (a node with label 2 is called a terminal), we consider the (1,2)-survivable network design problem and more precisely, the separation problem for the partition inequalities. We show that this separation problem reduces to a sequence of submodular flow problems. Based on an algorithm developed by Fujishige and Zhang th...

In this paper, we describe the problem of routing trains through a railway station. This routing problem is a subproblem of the automatic generation of timetables for the Dutch railway system. The problem of routing trains through a railway station is the problem of assigning each of the involved trains to a route through the railway station, given the detailed layout of the railway network wit...

We address the problem of computing a Walrasian equilibrium price in an ascending auction with gross substitutes valuations. In particular, an auction market is considered where there are multiple differentiated items and each item may have multiple units. Although the ascending auction is known to find an equilibrium price vector in finite time, little is known about its time complexity. The m...

A biclique is a maximal induced complete bipartite subgraph of a graph. We investigate the intersection structure of edge-sets of bicliques in a graph. Specifically, we study the associated edge-biclique hypergraph whose hyperedges are precisely the edge-sets of all bicliques. We characterize graphs whose edgebiclique hypergraph is conformal (i.e., it is the clique hypergraph of its 2-section) ...

On the basis of the concept of grades of a fuzzy point to belongingness (∈) or quasi-coincident (q) or belongingness and quasi-coincident (∈ ∧q) or belongingness or quasi-coincident (∈ ∨q) in an intuitionistic fuzzy set of a ring, the notion of a (α,β )intuitionistic fuzzy subring and ideal is introduced by applying the Lukasiewicz 3-valued implication operator. Using the notion of fuzzy cut se...

Let P be an optimization problem, and let A be an approximation algorithm for P . The domination ratio domr(A,n) is the maximum real q such that the solution x(I) obtained by A for any instance I of P of size n is not worse than at least a fraction q of the feasible solutions of I. We describe a deterministic, polynomial time algorithm with domination ratio 1−o(1) for the partition problem, and...

In this paper we describe a successful case-study where a Branch-and-Cut algorithm yields the “optimal” solution of a real-world timetabling problem for university courses (University Course Timetabling problem). The polyhedral structure of the problem is studied in conection with a polytope of the Set Packing problem. Several families of cutting planes are introduced, these being crutial to fi...

This paper describes components of a branch-and-cut algorithm for solving integer linear programs having a large symmetry group. It describes an isomorphism pruning algorithm and variable setting procedures using orbits of the symmetry group. Pruning and orbit computations are performed by backtracking procedures using a Schreier-Sims table for representing the symmetry group. Applications to h...

From the previous lecture, we have proved the following lemma. Lemma 1. If the cost vector c t ∈ [−ρ, ρ] n , and T ≥ 4ρ 2 ln n 2 , then average loss 1 T T t=1 p t c t ≤ 1 T T t=1 c t (i) + , ∀i ∈ [n] In this lecture, we are going to see the application of multi-weight algorithm for solving LPs and SDPs. For illustration purpose, we will be working on an LP example (the LP relaxation for set cov...