Rural Postman Problem Research Articles

Approximate Mechanisms for the Graphical TSP and Other Graph-Traversal Problems

Let G = (V,E) be a graph modeling a network in which each edge is owned by a selfish agent, which establishes the cost for traversing its edge (i.e., assigns a weight to its edge) by pursuing only its personal utility. In such a setting, we aim at designing approximate truthful mechanisms for several NP-hard traversal problems on G, such as the graphical traveling salesman problem, the rural postman problem, and the mixed Chinese postman problem, each of which in general requires an edge of G to be used several times. Thus, in game-theoretic terms, these are one-parameter problems, but with a peculiarity: the workload of each agent is a natural number. In this paper we refine the classical notion of monotonicity of an algorithm so as to capture exactly this property, and we then provide a general mechanism-design technique that guarantees this monotonicity and that allows one to compute efficiently the corresponding payments. In this way, we show that the former two problems and the latter one admit a 3/2...

Undirected postman problems with zigzagging option: A cutting-plane approach

The paper devises a new model and associated cutting-plane and branch-and-cut approaches for a variant of the undirected Chinese and rural postman problem where some of the edges offer the flexibility of either being serviced twice by two separate traversals or by a single zigzag traversal. The kernel of the proposed cutting-plane algorithm is a separation procedure for generalized blossom inequalities. We show that the currently best known separation procedure of Letchford, Reinelt and Theis [A faster exact separation algorithm for blossom inequalities. In: Nemhauser G, Bienstock D, editors, Integer programming and combinatorial optimization, vol. 3064. Berlin: Springer; 2004. (chapter 10)] is applicable and leads to a highly efficient solution approach which can handle large-scale problem instances.

Intelligent Deployment of Forest Road Graders

Road grading is the most common maintenance activity performed on forest roads. Reducing grading cost could release resources for other maintenance needs, ideally resulting in a better maintained road system. A combinatorial optimization method, tabu search, is combined with two local search procedures to generate efficient grading routes. Determining the optimal grading route is modeled as an extension of the Mixed Rural Postman Problem (MRPP), adapted to include a daily operating time limit and different traversal/service times. The objective was to minimize total operating time, a proxy for grading cost. The heuristic was tested on both artificial and actual forest road networks, and computational results are presented. The heuristic demonstrates the ability to generate efficient and feasible grader routes.

On the general routing polytope

The General Routing Problem ( GRP) consists of finding a minimum length closed walk in an edge-weighted undirected graph, subject to containing certain sets of required nodes and edges. It is related to the Rural Postman Problem and the Graphical Traveling Salesman Problem. We examine the 0/1-polytope associated with the GRP introduced by Ghiani and Laporte [A branch-and-cut algorithm for the Undirected Rural Postman Problem, Math. Program. Ser. A 87 (3) (2000) 467–481]. We show that whenever it is not full-dimensional, the set of equations and facets can be characterized, and the polytope is isomorphic to the full-dimensional polytope associated with another GRP instance which can be obtained in polynomial time. We also offer a node-lifting method. Both results are applied to prove the facet-defining property of some classes of valid inequalities. As a tool, we study more general polyhedra associated to the GRP.

Testing as Collecting of Evidence: An Integrated Approach to Test Generation for Finite State Machines

A new method to generate tests for deterministic implementations of deterministic finite state machines is proposed. The method is generic, taking a wide class of testing strategies as a parameter, and able to support both transition-oriented and fault-model-driven testing. For a given specification machine, it builds a graph encoding the given strategy and then generates a test by solving on the graph a generalization of the Rural Postman Problem. Only the first phase is domain specific and therefore precisely described in the paper. The second phase is considered a responsibility of graph specialists, though we provide guidelines for solving the most commonly encountered special case. The strategy encoding produced in the first phase is such that the second phase automatically handles, in an integrated manner, the following optimization concerns: absolute avoidance of forbidden transitions, maximum avoidance of transitions which are for some reason considered undesirable, subtest choice, subtest ordering and subtest connection, possibly with overlapping. The method accepts multi-criteria transition cost functions. If both its phases are executed precisely, it generates a test optimal with respect to the adopted strategy, and a strategy for generating absolutely optimal tests is also given. For the cases where the complexity of the first phase or of the resulting graph is problematic, guidelines for systematically conducting the phase in an approximate way are provided.

Lower bounds and heuristics for the Windy Rural Postman Problem

In this paper we present several heuristic algorithms and a cutting-plane algorithm for the Windy Rural Postman Problem. This problem contains several important Arc Routing Problems as special cases and has very interesting real-life applications. Extensive computational experiments over different sets of instances are also presented.

Heuristics for a dynamic rural postman problem

This paper presents a very special cutting path determination problem appearing in a high precision tools factory, and provides two new heuristics for its resolution. Particular features of both the cutting process, and of the material to be cut, bring in a set of unusual constraints, when compared with other cutting processes, which confer additional complexity and originality to the problem. In particular, this is a matter of practical and economic relevance, since the solution methods are intended to be implemented in a real-life industrial environment. The concept of dynamic graph is exploited to deal with the arc routing problem under study, which is modelled as a dynamic rural postman problem. The constructive heuristics developed, the “higher up vertex heuristic” (HUV) and the “minimum empty path heuristic” (MEP) are tested with real data sets.

Zigzag inequalities: a new class of facet-inducing inequalities for Arc Routing Problems

In this paper we introduce a new class of facet-inducing inequalities for the Windy Rural Postman Problem and the Windy General Routing Problem. These inequalities are called Zigzag inequalities because they cut off fractional solutions containing a zigzag associated with variables with 0.5 value. Two different types of inequalities, the Odd Zigzag and the Even Zigzag inequalities, are presented. Finally, their application to other known Arc Routing Problems is discussed.

New heuristic algorithms for the windy rural postman problem

In this paper we deal with the windy rural postman problem. This problem generalizes several important arc routing problems and has interesting real-life applications. Here, we present several heur...

A constructive heuristic for the Undirected Rural Postman Problem

This paper describes a constructive heuristic for the well-known Undirected Rural Postman Problem. At each iteration, the procedure inserts a connected component of the required edges and performs a local postoptimization. Computational results on a set of benchmark instances with up to 350 vertices show that the proposed procedure is competitive with the classical Frederickson procedure. Its use is recommended when a high-quality solution is needed in a short amount of time (e.g., in laser plotter applications).

Approximate solutions for the maximum benefit chinese postman problem

The Maximum Benefit Chinese Postman Problem (MBCPP) is an interesting and practical generalization of the classical Chinese Postman Problem, which has many real-world applications. Each arc on the MBCPP network is associated with a service cost for the traversal with service, a deadhead cost for the traversal with no service, and a set of benefits. Each time an arc is traversed, a benefit is generated. The objective of the MBCPP is to find a postman tour traversing a selected set of arcs with the total net benefit maximized. Such a generalization reflects real-world situations more closely. The MBCPP has been shown to be more complicated than the Rural Postman Problem, which is an NP-hard problem. Therefore, it is difficult to find polynomial-time bounded algorithms to solve the problem exactly. In this paper, we first review an existing exact solution procedure, and introduce several heuristic algorithms including the Branch-Scan algorithm, the Connection algorithm with various connection strategies, and the Directed Tree algorithm, to solve the MBCPP approximately. We also apply one-opt, two-opt, component exchange, and component-drop procedures to improve the solutions. The proposed algorithms are tested and compared. Extensive computational results are provided and analysed.

Efficient heuristics for the Rural Postman Problem

A local search framework for the (undirected) Rural Postman Problem (RPP) is presented in this paper. The framework allows local search approaches that have been applied successfully to the well–known Travelling Salesman Problem also to be applied to the RPP. New heuristics for the RPP, based on this framework, are introduced and these are capable of solving significantly larger instances of the RPP than have been reported in the literature. Test results are presented for a number of benchmark RPP instances in a bid to compare efficiency and solution quality against known methods.

Privatized rural postman problems

In this work we analyze the privatized rural postman problem which is the edge version of the traveling salesman problems with profits. The problem is defined on a undirected graph G ( V , E ) with a distinguished vertex d, called the Depot. There are two non-negative real functions on the edge set E, which define the value of a cycle in G: one is the profit function, b, and the other one is the cost function, c. They have different meanings when a cycle C traverses an edge e (possibly more than once), because we pay a cost c e every time e is traversed, but we collect the profit b e only the first time e is traversed. The privatized rural postman problem is to find a cycle C ★ , passing through d and not necessarily simple, which maximizes the sum of the values of the edges traversed in C ★ . That is, max C ∑ e ∈ C ( b e - t e c e ) where t e is the number of times that edge e is traversed in C. We study some properties of the problem: we show that it is NP-hard, its relation with known and new problems, and special cases with good algorithms. We also analyze several integer linear systems of inequalities, which define the polyhedral structure of the problem, and we give dominance and preprocessing conditions. We finish with some remarks and comments about future research.

Transformation of Facets of the General Routing Problem Polytope

We study the class of polytopes associated with the 0/1-variable formulation by [G. Ghiani and G. Laporte, Math. Program., 87 (2000), pp. 467--481] of the rural postman problem and general routing problem. We introduce a technique called switching, which allows one to obtain new valid or facet-defining inequalities from known ones. We study the switched forms which can be obtained from two important types of known valid inequalities, namely, so called path-bridge [A. N. Letchford, Eur. J. Oper. Res., 96 (1997), pp. 317--322] and honeycomb [A. Corberan and J. M. Sanchis, Eur. J. Oper. Res., 108 (1998), pp. 538--550] inequalities. For the switched path-bridge inequalities, a generic blueprint for separation routines is developed. We give a polynomial time separation algorithm for a special subclass of these inequalities.

Network service scheduling and routing

AbstractReal‐life vehicle routing problems generally have both routing and scheduling aspects to consider. Although this fact is well acknowledged, few heuristic methods exist that address both these complicated aspects simultaneously. We present a graph theoretic heuristic to determine an efficient service route for a single service vehicle through a transportation network that requires a subset of its edges to be serviced, each a specified (potentially different) number of times. The times at which each of these edges are to be serviced should additionally be as evenly spaced over the scheduling time window as possible, thus introducing a scheduling consideration to the problem. Our heuristic is based on the tabu search method, used in conjunction with various well‐known graph theoretic algorithms, such as those of Floyd (for determining shortest routes) and Frederickson (for solving the rural postman problem). This heuristic forms the backbone of a decision support system that prompts the user for certain parameters from the physical situation (such as the service frequencies and travel times for each network link as well as bounds in terms of acceptability of results) after which a service routing schedule is suggested as output. The decision support system is applied to a special case study, where a service routing schedule is sought for the South African national railway system by Spoornet (the semi‐privatised South African national railways authority and service provider) as part of their rationalisation effort, in order to remain a lucrative company.

New heuristic algorithms for the windy rural postman problem

In this paper we deal with the windy rural postman problem. This problem generalizes several important arc routing problems and has interesting real-life applications. Here, we present several heuristics whose study has lead to the design of a scatter search algorithm for the windy rural postman problem. Extensive computational experiments over different sets of instances, with sizes up to 988 nodes and 3952 edges, are also presented.

Solving the hierarchical Chinese postman problem as a rural postman problem

In the undirected hierarchical Chinese postman problem (HCPP), the edges of a graph are partitioned into clusters and must be serviced while respecting a hierarchy, or precedence relation, between clusters. Two objectives are considered: a hierarchical objective and a makespan objective. In this article, a transformation of the HCPP into an equivalent rural postman problem (RPP) is presented. The HCPP is solved optimally, for both objectives, by applying an exact branch-and-cut RPP algorithm to the transformed problem. Two heuristics based on the RPP algorithm are also described and assessed computationally.

A heuristic for the periodic rural postman problem

The periodic rural postman problem (PRPP) is variant of the classical rural postman problem whose applications arise in garbage collection and street sweeping. In the PRPP each required arc/edge of a graph must be visited a given number of times over an m-day planning period in such a way that service days are equally spaced. The PRPP amounts to select a service day combination for each required arc/edge and to determine a postman tour for each day of the planning period. The objective is to minimize the total distance travelled. In this paper a simple but effective heuristic for the undirected PRPP is presented. Extensive computational results indicate that the algorithm is capable of providing high quality solutions. To our knowledge this is the first methodological paper devoted to a periodic arc routing problem.

Exact solution of the generalized routing problem through graph transformations

In the general routing problem, the aim is to determine a least cost traversal of a subset of edges, arcs and vertices of a graph. The problem can be transformed into an equivalent traveling salesman problem or rural postman problem and solved optimally. Computational results are reported.

On the Maximum Benefit Chinese Postman Problem

The Maximum Benefit Chinese Postman Problem (MBCPP) is a practical generalization of the classical Chinese Postman Problem (CPP), which has many real-world applications. In this paper, we consider the MBCPP on undirected networks, and show that the MBCPP is more complex than the Rural Postman Problem (RPP). We present a sufficient condition for the MBCPP solution to cover the whole network, and provide an upper bound. Based on the upper bound, we propose an efficient solution procedure to solve the MBCPP approximately. The proposed algorithm applies the minimal spanning tree and the minimal-cost matching algorithms, which performs well on problems satisfying the sufficient condition.