Malcolm Yoke Hean Low

A bee colony optimization algorithm to job shop scheduling

In the face of globalization and rapidly shrinking product life cycle, manufacturing companies are trying different means to improve productivity through management of machine utilization and product cycle-time. Job shop scheduling is an important task for manufacturing industry in terms of improving machine utilization and reducing cycle-time. However, job shop scheduling is inherently a NP-hard problem with no easy solution. This paper describes a novel approach that uses the honey bees foraging model to solve the job shop scheduling problem. Experimental results comparing the proposed honey bee colony approach with existing approaches such as ant colony and tabu search are presented

A Bee Colony Optimization Algorithm for Traveling Salesman Problem

A bee colony optimization (BCO) algorithm for traveling salesman problem (TSP) is presented in this paper. The BCO model is constructed algorithmically based on the collective intelligence shown in bee foraging behaviour. Experimental results comparing the proposed BCO model with some existing approaches on a set of benchmark problems are presented.

Crowd modeling and simulation technologies

As a collective and highly dynamic social group, the human crowd is a fascinating phenomenon that has been frequently studied by experts from various areas. Recently, computer-based modeling and simulation technologies have emerged to support investigation of the dynamics of crowds, such as a crowds behaviors under normal and emergent situations. This article assesses the major existing technologies for crowd modeling and simulation. We first propose a two-dimensional categorization mechanism to classify existing work depending on the size of crowds and the time-scale of the crowd phenomena of interest. Four evaluation criteria have also been introduced to evaluate existing crowd simulation systems from the point of view of both a modeler and an end-user. We have discussed some influential existing work in crowd modeling and simulation regarding their major features, performance as well as the technologies used in this work. We have also discussed some open problems in the area. This article will provide the researchers with useful information and insights on the state of the art of the technologies in crowd modeling and simulation as well as future research directions.

BEE COLONY OPTIMIZATION WITH LOCAL SEARCH FOR TRAVELING SALESMAN PROBLEM

Many real world industrial applications involve finding a Hamiltonian path with minimum cost. Some instances that belong to this category are transportation routing problem, scan chain optimization and drilling problem in integrated circuit testing and production. This paper presents a bee colony optimization (BCO) algorithm for traveling salesman problem (TSP). The BCO model is constructed algorithmically based on the collective intelligence shown in bee foraging behaviour. The model is integrated with 2-opt heuristic to further improve prior solutions generated by the BCO model. Experimental results comparing the proposed BCO model with existing approaches on a set of benchmark problems are presented.

Integrating heterogeneous distributed COTS discrete-event simulation packages: an emerging standards-based approach

This paper reports on the progress made toward the emergence of standards to support the integration of heterogeneous discrete-event simulations (DESs) created in specialist support tools called commercial-off-the-shelf (COTS) discrete-event simulation packages (CSPs). The general standard for heterogeneous integration in this area has been developed from research in distributed simulation and is the IEEE 1516 standard The High Level Architecture (HLA). However, the specific needs of heterogeneous CSP integration require that the HLA is augmented by additional complementary standards. These are the suite of CSP interoperability (CSPI) standards being developed under the Simulation Interoperability Standards Organization (SISO-http://www.sisostds.org) by the CSPI Product Development Group (CSPI-PDG). The suite consists of several interoperability reference models (IRMs) that outline different integration needs of CSPI, interoperability frameworks (IFs) that define the HLA-based solution to each IRM, appropriate data exchange representations to specify the data exchanged in an IF, and benchmarks termed CSP emulators (CSPEs). This paper contributes to the development of the Type I IF that is intended to represent the HLA-based solution to the problem outlined by the Type I IRM (asynchronous entity passing) by developing the entity transfer specification (ETS) data exchange representation. The use of the ETS in an illustrative case study implemented using a prototype CSPE is shown. This case study also allows us to highlight the importance of event granularity and lookahead in the performance and development of the Type I IF, and to discuss possible methods to automate the capture of appropriate values of lookahead.

Symbiotic Simulation Systems: An Extended Definition Motivated by Symbiosis in Biology

Although various forms of symbiosis are known in biology, only mutualism has been considered in the context of symbiotic simulation systems. In this paper, we explain why the original definition of symbiotic simulation systems is narrow and why it is important to consider other forms of symbiosis as well. As a consequence we propose an extended definition of symbiotic simulation systems motivated by symbiosis in biology. By using this extended definition, we identify five different types of symbiotic simulation systems which can be applied in various applications. We describe how single systems can be combined and propose a hybrid symbiotic simulation system in the context of semiconductor manufacturing.

An efficient Bee Colony Optimization algorithm for Traveling Salesman Problem using frequency-based pruning

In a bee colony, bees perform waggle dance in order to communicate the information of food source to their hive mates. This foraging behaviour has been adapted in a Bee Colony Optimization (BCO) algorithm together with 2-opt local search to solve the Traveling Salesman Problem (TSP) [1]. To reduce the high overhead incurred by 2-opt in the BCO algorithm proposed previously, two mechanisms named frequency-based pruning strategy (FBPS) and fixed-radius near neighbour (FRNN) 2-opt are presented. FBPS suggests that only a subset of promising solutions are allowed to perform 2-opt based on the accumulated frequency of its building blocks recorded in a matrix. FRNN 2-opt is an efficient implementation of 2-opt which exploits the geometric structure in a permutation of TSP sequence. Both mechanisms are tested on a set of TSP benchmark problems and the results show that they are able to achieve a 58.42% improvement while maintaining the solution quality at 0.02% from known optimal.

Dynamic yard crane dispatching in container terminals with predicted vehicle arrival information

The performance of a container terminal depends on many aspects of operations. This paper focuses on the optimal sequencing of a yard crane (or YC for short) for serving a fleet of vehicles for delivery and pickup jobs. The objective is to minimize the average vehicle waiting time. While heuristic algorithms could not guarantee an optimal solution, a conventional mathematical formulation such as mixed integer program would require too much computing time. We present two new algorithms to efficiently compute YC dispatching sequences that are provably optimal within the planning window. The first algorithm is based on the well-known A^* search along with an admissible heuristics. We also incorporate this heuristics into a second backtracking algorithm which uses a prioritized search order to accelerate the computation. Experimental results show that both new algorithms perform very well for realistic YC jobs. Specifically, both are able to find within seconds optimal solutions for heavy workload scenarios with over 2.4x10^1^8 possible dispatching sequences. Moreover, even when the vehicle arrival times are not accurately forecasted, the new algorithms are still robust enough to produce optimal or near-optimal sequences, and they consistently outperform all the other algorithms evaluated.

Optimistic Synchronization in HLA-Based Distributed Simulation

With the wide use of commercial off-the-shelf (COTS) simulation packages and the advent of the High Level Architecture (HLA) standard, it is desirable to build distributed simulations by linking various types of simulation models developed using best-fit COTS packages. While almost all current work on integrating COTS packages and the HLA is based on conservative synchronization, it is worthwhile to investigate the optimistic synchronization approach. The optimistic approach can exploit parallelism and achieve promising performance in situations where causality errors may occur but in fact seldom occur. The authors introduce a rollback controller using a middleware approach to handle the complex rollback procedure on behalf of the simulation model. A new time advance algorithm is proposed that can fully use the benefits of optimistic synchronization. The article also describes a scalability study showing the experimental results for the two synchronization approaches as the number of simulation components increases.

Federate migration in HLA-based simulation

The High Level Architecture (HLA) promotes simulation interoperability and reusability, making it an ideal candidate to model large-scale systems. However, a large-scale simulation running in a distributed environment is often affected by the imbalance of load level at different computing hosts. Migrating simulation components from heavily-loaded hosts to less-loaded ones can solve the problem. Protocols to migrate HLA simulation federates have been introduced by various research projects. However, existing protocols achieve migration by using either federation wide synchronization or a third party host, such as FTP servers, to handle the saving and restoring of migration states. We have previously developed a framework to execute HLA-based simulations in the Grid environment with migration support as a prominent design feature. Based on the framework, a federate migration protocol that bypasses the shortcomings identified above has been developed and better migration performance is achieved. To eliminate message loss during the migration process, a counter mechanism is employed. Studies also show that federate join time contributes significantly to the migration overhead. Therefore, our protocol overlaps the simulation execution of the federate to be migrated and the join federation operation performed by the restarting federate at the migration destination. In this paper, the development of our protocol is described and experimental results with comparison to the approach using federation wide synchronization are discussed.