Wyniki wyszukiwania - BazTech

1

Exact and approximation algorithms for joint routing and flow rate optimization

Junosza-Szaniawski Konstanty, Nogalski Dariusz

Annals of Computer Science and Information Systems

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2019

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Vol. 20

29--36

EN

This paper addresses comparison of algorithms for a version of the NUM problem. The joint formulation of routing and transmission rate control within the multi-user and single-path setting is assumed within the NUM. Since problem is NP-hard, the efficient heuristics are designed, implemented and compared experimentally with other existing heuristics and exact linear programming solver. The linear approximation is applied for nonlinear utility function. The results of experiments demonstrate a trade-off between computing time and precision of goal value.

2

Correlation clustering: Let all the flowers bloom!

Aszalós László, Bakó Mária

Annals of Computer Science and Information Systems

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2019

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Vol. 20

21--28

EN

Correlation clustering is a NP-hard problem, and for large signed graphs finding even just a good approximation of the optimal solution is a hard task. In this article we examine the effect of ranking of the nodes and process them in order of ranks. We present that based on the rate of positive edges in the graph we should use different optimization methods. We show that all the building blocks of our methods are needed under certain circumstances.

3

Hybridization of the optimization process as an alternative way to find approximate solutions for NP-hard problems

Rozenberg L., Rychcicki R.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 2

59-62

EN

This paper presents the results of calculations that demonstrate the possibility of using hybrid optimization method (with variable structure) for determining the approximate solutions to NP-hard problems. The Travelling Salesman Problem (TSP) is a classic combinatorial optimization subject, which has found widespread use in practice. Simple in definition, have remained hard to solve for many years. Not only an efficient solution would yield benefits in a substantial amount of routing problems, but it would also affect planning and logistics in a positive way.

PL

W prezentowanym artykule pokazano możliwość wykorzystania hybrydy optymalizacyjnej do uzyskania przybliżonego rozwiązania zadania NP-trudnego, czyli problemu obliczeniowego o ponad wykładniczym zapotrzebowaniu na moc obliczeniową. Do badań wybrano znany od wielu lat problem komiwojażera, którego od lat nie udało się ostatecznie rozwiązać. Wybór ten jednak umożliwił uzyskanie pokaźnego materiału porównawczego.

4

Algorytm hybrydowy wielokrotnego startu dla rozwiązywania problemu sekwencyjnego uporządkowania

Widuch J., Klyta A.

Studia Informatica

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2014

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Vol. 35, nr 1

29--55

PL

Problem sekwencyjnego uporządkowania (SOP) jest podobny do asymetrycznego problemu komiwojażera. Celem jest wyznaczenie w skierowanym grafie ważonym ścieżki Hamiltona o minimalnej wadze, przy dodatkowym spełnieniu relacji pierwszeństwa wierzchołków. W niniejszej pracy zaprezentowano algorytm hybrydowy wielokrotnego startu rozwiązywania problemu SOP. Algorytm ten jest połączeniem algorytmów symulowanego wyżarzania i lokalnej optymalizacji. Dodatkowo przedstawiono wyniki przeprowadzonych badań eksperymentalnych.

EN

The sequential ordering problem (SOP) is similar to the asymmetric traveling salesman problem. The goal is to find a minimum weight Hamiltonian path on a directed weighted graph satisfying precedence relationships among the vertices. In the paper, a multistart hybrid algorithm to solving SOP is presented. The algorithm based on simulated annealing algorithm and local optimization method. Apart from that results of experimental tests are presented.

5

Complexity of Searching for a Black Hole

Czyzowicz J., Kowalski D., Markou E., Pelc A.

Fundamenta Informaticae

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2006

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Vol. 71, nr 2,3

229-242

EN

A black hole is a highly harmful stationary process residing in a node of a network and destroying all mobile agents visiting the node, without leaving any trace. We consider the task of locating a black hole in a (partially) synchronous network, assuming an upper bound on the time of any edge traversal by an agent. The minimum number of agents capable to identify a black hole is two. For a given graph and given starting node we are interested in the fastest possible black hole search by two agents, under the general scenario in which some subset of nodes is safe and the black hole can be located in one of the remaining nodes. We show that the problem of finding the fastest possible black hole search scheme by two agents is NP-hard, and we give a 9.3-approximation for it.