scholarly journals A Hybrid Method for the Modelling and Optimisation of Constrained Search Problems

2014 ◽  
Vol 5 (3) ◽  
pp. 7-22 ◽  
Author(s):  
Pawel Sitek ◽  
Jaroslaw Wikarek
Keyword(s):  
Integer Programming ◽  
Logic Programming ◽  
Hybrid Method ◽  
Vehicle Routing Problem ◽  
Hybrid Approach ◽  
Constraint Logic Programming ◽  
Decision Models ◽  
Routing Problem ◽  
Constrained Problems ◽  
Decision Variables

AbstractThe paper presents a concept and the outline of the implementation of a hybrid approach to modelling and solving constrained problems. Two environments of mathematical programming (in particular, integer programming) and declarative programming (in particular, constraint logic programming) were integrated. The strengths of integer programming and constraint logic programming, in which constraints are treated in a different way and different methods are implemented, were combined to use the strengths of both. The hybrid method is not worse than either of its components used independently. The proposed approach is particularly important for the decision models with an objective function and many discrete decision variables added up in multiple constraints. To validate the proposed approach, two illustrative examples are presented and solved. The first example is the authors’ original model of cost optimisation in the supply chain with multimodal transportation. The second one is the two-echelon variant of the well-known capacitated vehicle routing problem.

scholarly journals A Hybrid Approach to the Optimization of Multiechelon Systems

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Paweł Sitek ◽  
Jarosław Wikarek
Keyword(s):  
Mathematical Programming ◽  
Vehicle Routing ◽  
Vehicle Routing Problem ◽  
Hybrid Approach ◽  
Decision Models ◽  
Data Sets ◽  
Routing Problem ◽  
Capacitated Vehicle Routing Problem ◽  
Decision Variables ◽  
Capacitated Vehicle

In freight transportation there are two main distribution strategies: direct shipping and multiechelon distribution. In the direct shipping, vehicles, starting from a depot, bring their freight directly to the destination, while in the multiechelon systems, freight is delivered from the depot to the customers through an intermediate points. Multiechelon systems are particularly useful for logistic issues in a competitive environment. The paper presents a concept and application of a hybrid approach to modeling and optimization of the Multi-Echelon Capacitated Vehicle Routing Problem. Two ways of mathematical programming (MP) and constraint logic programming (CLP) are integrated in one environment. The strengths of MP and CLP in which constraints are treated in a different way and different methods are implemented and combined to use the strengths of both. The proposed approach is particularly important for the discrete decision models with an objective function and many discrete decision variables added up in multiple constraints. An implementation of hybrid approach in theECLiPSesystem using Eplex library is presented. The Two-Echelon Capacitated Vehicle Routing Problem (2E-CVRP) and its variants are shown as an illustrative example of the hybrid approach. The presented hybrid approach will be compared with classical mathematical programming on the same benchmark data sets.

scholarly journals A Cluster-First Route-Second Heuristic Approach to Solve The Multi-Trip Periodic Vehicle Routing Problem

2019 ◽  
Vol 20 (2) ◽  
pp. 68
Author(s):  
Annisa Kesy Garside ◽  
Nabila Rohmatul Laili
Keyword(s):  
Integer Programming ◽  
Vehicle Routing ◽  
Vehicle Routing Problem ◽  
Phase 1 ◽  
Working Hours ◽  
Real Problem ◽  
Phase 2 ◽  
Routing Problem ◽  
Periodic Vehicle Routing Problem ◽  
Periodic Vehicle Routing

This paper discusses periodic vehicle routing problems that allow vehicles to travel on multiple trips in a single day. It is known as the Multi-Trip Periodic Vehicles (MTPVRP) Problem Route. Cluster-first route-second (CFRS) heuristics to solve MTPVRP was proposed in this study. In phase 1, customers were divided into clusters using the formulation of integer programming. Phase 2 determined the route of the cluster and verifies that the total journey time to visit the trips does not exceed the working hours of the vehicle. The implementation of the heuristic CFRS to solve the real problem faced by the LPG distributor shows that the procedure could provide a better routing solution.

scholarly journals SEQUENCING IN A NON-PERMUTATION FLOWSHOP WITH CONSTRAINED BUFFERS: APPLICABILITY OF GENETIC ALGORITH VERSUS CONSTRAINT LOGIC PROGRAMMING

2008 ◽  
pp. 69-78
Author(s):  
Gerrit Farber ◽  
Said Salhi ◽  
Anna M. Coves Moreno
Keyword(s):  
Genetic Algorithm ◽  
Logic Programming ◽  
Production Line ◽  
Mixed Model ◽  
Hybrid Approach ◽  
Constraint Logic Programming ◽  
Arbitrary Sequence ◽  
Production Lines ◽  
Permutation Flowshop ◽  
The Difference

Mixed model production lines consider more than one model being processed on the same production line in an arbitrary sequence. Nevertheless, the majority of publications in this area are limited to solutions which determine the job sequence before the jobs enter the line and maintains it without interchanging jobs until the end of the production line, which is known as permutation flowshop. This paper considers a nonpermutation flowshop. Resequencing is permitted where stations have access to intermediate or centralized resequencing buffers. The access to the buffers is restricted by the number of available buffer places and the physical size of the products. Two conceptually different approaches are presented in order to solve the problem. The first approach is a hybrid approach, using Constraint Logic Programming (CLP), whereas the second one is a Genetic Algorithm (GA). Improvements that come with the introduction of constrained resequencing buffers are highlighted. Characteristics such as the difference between the intermediate and the centralized case are analyzed, and the special case of semi dynamic demand is studied. Finally, recommendations are presented for the applicability of the hybrid approach, using CLP, versus the Genetic Algorithm.

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