Browsing by Subject "heuristics"

Now showing 1 - 6 of 6

Access status: Open Access ,
A transfer line balancing problem by heuristic methods: industrial case studies
(2008) Guschinskaya, Olga; Dolgui, Alexandre
The paper deals with the problem of optimal configuration of a type of transfer lines which are equipped with transfer machines. Such machines perform operations with standard modular spindle heads which are activated sequentially. All operations assigned to the same spindle head (block of operations) are executed simultaneously by a set of tools fixed at the spindle head. The quantity of machines and spindle heads used to produce a part with the given productivity rate defines the final cost of the transfer line which must be minimized. To minimize this cost, a combinatorial problem of operations assignment to blocks and machines must be solved. The solution must provide a desired productivity (cycle time), it must also satisfy precedence and compatibility constraints. In this paper, we suggest improved versions of FSIC heuristic algorithm in order to help line designers to solve real-scale industrial problems. Results of computational experiments obtained for industrial cases are presented.
Access status: Open Access ,
A two-phase algorithm for a Resource Constrained Project Scheduling Problem with Discounted Cash Flows
(2013) Klimek, Marcin; Łebkowski, Piotr
This paper presents a Resource-Constrained Project Scheduling Problem (RCPSP) settled by contractual milestones. The criterion analysed here is the maximisation of aggregate discounted cash flows from the contractor's perspective, known as an RCPSP problem with Discounted Cash Flows (RCPSPDCF). The cash flows analysed here cover the contractor´s cash outflows (negative cash flows), related to the commencement of individual activities, and cash inflows (positive cash flows) after the fulfilment of individual milestones. The authors propose a two-phase algorithm for solving the problem defined. In the first phase, the simulated annealing metaheuristics is used, designed to identify a forward schedule with as high total DCF as possible. In the second phase, the best first-phase schedule is improved by right shifts of activities. To this end, the procedure which iteratively shifts tasks by one unit is applied, with a view to maximising the objective function. Activity shifts take into consideration precedence and resource constraints, and they are performed for a specified resource allocation to activities. This paper also includes an analysis of the problem for a sample project. The results of computational experiments are then analysed. The experiments were run with the use of standard test problems from the Project Scheduling Problem LIBrary (PSPLIB), with additionally defined cash flows and contractual milestones.
Access status: Open Access ,
Block approach-local search algorithm for single machine total weighted tardiness problem
(Wydawnictwa AGH, 2005) Bożejko, Wojciech; Grabowski, Józef; Wodecki, Mieczysław
W pracy rozpatrujemy problem szeregowania zadań na jednej maszynie z minimalizacją sumy kosztów opóźnień. Przedstawiamy szereg nowych własności pozwalających na rozbicie permutacji (rozwiązania dopuszczalnego) na podciągi, zwane blokami. Dzięki temu, z otoczeń generowanych przez ruchy typu zamień lub wstaw, eliminujemy wiele rozwiązań nie gwarantujących poprawę wartości funkcji celu. Algorytm oparty na metodzie poszukiwania z zabronieniami (tabu search), w którym stosuje się te otoczenia, działa bardzo szybko, a otrzymane wyniki są lepsze niż inne wyniki opisane w literaturze algorytmów.
Access status: Open Access ,
Heuristic algorithm for lot sizing and scheduling on identical parallel machines
(Wydawnictwa AGH, 2022) Książek, Roger
This paper presents a new heuristic algorithm for the task of lot sizing and scheduling for identical parallel machines. The new algorithm is based on the rolling-horizon approach and the fix-and-relax decomposition technique. Two variants of the algorithm are finally proposed for solving the problem of lot scheduling with parallel machines where the number of products and machines is greater than that of the machines. A computational experiment has been conducted for a group of 30 data sets. The results showed that the new algorithm efficiently provided good solutions for tasks with large numbers of machines and products.
Access status: Open Access ,
Policy-based sla storagemanagement model fordistributeddata storage services
(Wydawnictwa AGH, 2018) Nikolow, Darin; Słota, Renata; Polak, Stanisław; Pogoda, Marek; Kitowski, Jacek
There is high demand for storage related services supporting scientists in their research activities. Those services are expected to provide not only capacity but also features allowing for more exible and cost ecient usage. Such features include easy multiplatform data access, long term data retention, support for performance and cost dierentiating of SLA restricted data access. The paper presents a policy-based SLA storage management model for distributed data storage services. The model allows for automated management of distributed data aimed at QoS provisioning with no strict resource reservation. The problem of providing users with the required QoS requirements is complex, and therefore the model implements heuristic approach for solving it. The corresponding system architecture, metrics and methods for SLA focused storage management are developed and tested in a real, nationwide environment. Keywords distributed storage systems, quality of service, service level agreement, management model, heuristics.
Access status: Open Access ,
Two-level of production scheduling for flow-shop systems with intermediate storages
(AGH University of Science and Technology Press, 2008) Magiera, Marek
The paper presents relaxation heuristics for production planning for multistage flow-shop with intermediate storages. The top-level is a stage loading, i.e., allocation of operations to the stages. The base-level is a task scheduling - allocation of operations to the stations. The time criterion is used in the minimisation function - the minimal production schedule is fixed. Results of computational experiments with the proposed method are presented.