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Wyświetlanie 1-8 z 8
Tytuł:
An attractive class of bipartite graphs
Autorzy:
Boliac, Rodica
Lozin, Vadim
Powiązania:
https://bibliotekanauki.pl/articles/743515.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
bipartite graphs
structural characterization
polynomial algorithm
Opis:
In this paper we propose a structural characterization for a class of bipartite graphs defined by two forbidden induced subgraphs. We show that the obtained characterization leads to polynomial-time algorithms for several problems that are NP-hard in general bipartite graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2001, 21, 2; 293-301
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scheduling of Identical Jobs with Bipartite Incompatibility Graphs on Uniform Machines. Computational Experiments
Autorzy:
Duraj, S.
Kopeć, P.
Kubale, M.
Pikies, T.
Powiązania:
https://bibliotekanauki.pl/articles/376001.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
batch scheduling
bipartite graph
polynomial algorithm
uniform machines
Opis:
In this paper, we consider the problem of scheduling unit-length jobs on three or four uniform parallel machines to minimize the schedule length or total completion time. We assume that the jobs are subject to some types of mutual exclusion constraints, modeled by a bipartite graph of a bounded degree. The edges of the graph correspond to the pairs of jobs that cannot be processed on the same machine. Although the problem is generally NP-hard, we show that our problem can be solved to optimality in polynomial time under some restrictions imposed on the number of machines, their speeds, and the structure of the incompatibility graph. The theoretical considerations are accompanied by computer experiments with a certain model of scheduling.
Źródło:
Decision Making in Manufacturing and Services; 2017, 11, 1-2; 53-61
1896-8325
2300-7087
Pojawia się w:
Decision Making in Manufacturing and Services
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Persistency in the Traveling Salesman Problem on Halin graphs
Autorzy:
Lacko, Vladimír
Powiązania:
https://bibliotekanauki.pl/articles/743793.pdf
Data publikacji:
2000
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
persistency
traveling salesman problem
Halin graph
polynomial algorithm
Opis:
For the Traveling Salesman Problem (TSP) on Halin graphs with three types of cost functions: sum, bottleneck and balanced and with arbitrary real edge costs we compute in polynomial time the persistency partition $E_{All}$, $E_{Some}$, $E_{None}$ of the edge set E, where:
$E_{All}$ = {e ∈ E, e belongs to all optimum solutions},
$E_{None}$ = {e ∈ E, e does not belong to any optimum solution} and
$E_{Some}$ = {e ∈ E, e belongs to some but not to all optimum solutions}.
Źródło:
Discussiones Mathematicae Graph Theory; 2000, 20, 2; 231-242
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Note on Polynomial Algorithm for Cost Coloring of Bipartite Graphs with Δ ≤ 4
Autorzy:
Giaro, Krzysztof
Kubale, Marek
Powiązania:
https://bibliotekanauki.pl/articles/31526308.pdf
Data publikacji:
2020-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
bipartite graph
chromatic sum
cost coloring
NP-completeness
polynomial algorithm
Opis:
In the note we consider vertex coloring of a graph in which each color has an associated cost which is incurred each time the color is assigned to a vertex. The cost of coloring is the sum of costs incurred at each vertex. We show that the minimum cost coloring problem for n-vertex bipartite graph of degree Δ ≤ 4 can be solved in O(n2) time. This extends Jansen’s result [K. Jansen, The optimum cost chromatic partition problem, in: Proc. CIAC’97, Lecture Notes in Comput. Sci. 1203 (1997) 25–36] for paths and cycles to subgraphs of biquartic graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 3; 885-891
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spanning trees with many or few colors in edge-colored graphs
Autorzy:
Broersma, Hajo
Li, Xueliang
Powiązania:
https://bibliotekanauki.pl/articles/971955.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-coloring
spanning tree
matroid (intersection)
complexity
NP-complete
NP-hard
polynomial algorithm
(minimum) dominating set
Opis:
Given a graph G = (V,E) and a (not necessarily proper) edge-coloring of G, we consider the complexity of finding a spanning tree of G with as many different colors as possible, and of finding one with as few different colors as possible. We show that the first problem is equivalent to finding a common independent set of maximum cardinality in two matroids, implying that there is a polynomial algorithm. We use the minimum dominating set problem to show that the second problem is NP-hard.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 2; 259-269
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scheduling of unit-length jobs with bipartite incompatibility graphs on four uniform machines
Autorzy:
Furmańczyk, H.
Kubale, M.
Powiązania:
https://bibliotekanauki.pl/articles/200295.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
equitable coloring
NP-hardness
polynomial algorithm
scheduling
uniform machine
kolorowanie grafów
twardość NP
algorytm wielomianowy
planowanie
Opis:
In the paper we consider the problem of scheduling n identical jobs on 4 uniform machines with speeds s1 ≥ s2 ≥ s3 ≥ s4, respectively. Our aim is to find a schedule with a minimum possible length. We assume that jobs are subject to some kind of mutual exclusion constraints modeled by a bipartite incompatibility graph of degree Δ, where two incompatible jobs cannot be processed on the same machine. We show that the general problem is NP-hard even if s1 = s2 = s3. If, however, Δ ≤ 4 and s1 ≥ 12s2, s2 = s3 = s4, then the problem can be solved to optimality in time O(n1.5). The same algorithm returns a solution of value at most 2 times optimal provided that s1 ≥ 2s2. Finally, we study the case s1 ≥ s2 ≥ s3 = s4 and give a 32/15-approximation algorithm running also in O(n1.5) time.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2017, 65, 1; 29-34
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Equitable Colorings Of Corona Multiproducts Of Graphs
Autorzy:
Furmánczyk, Hanna
Kubale, Marek
Mkrtchyan, Vahan V.
Powiązania:
https://bibliotekanauki.pl/articles/31341573.pdf
Data publikacji:
2017-11-27
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
corona graph
equitable chromatic number
equitable coloring conjecture
equitable graph coloring
multiproduct of graphs
NP-completeness
polynomial algorithm
Opis:
A graph is equitably k-colorable if its vertices can be partitioned into k independent sets in such a way that the numbers of vertices in any two sets differ by at most one. The smallest k for which such a coloring exists is known as the equitable chromatic number of G and denoted by χ=(G). It is known that the problem of computation of χ=(G) is NP-hard in general and remains so for corona graphs. In this paper we consider the same model of coloring in the case of corona multiproducts of graphs. In particular, we obtain some results regarding the equitable chromatic number for the l-corona product G ◦l H, where G is an equitably 3- or 4-colorable graph and H is an r-partite graph, a cycle or a complete graph. Our proofs are mostly constructive in that they lead to polynomial algorithms for equitable coloring of such graph products provided that there is given an equitable coloring of G. Moreover, we confirm the Equitable Coloring Conjecture for corona products of such graphs. This paper extends the results from [H. Furmánczyk, K. Kaliraj, M. Kubale and V.J. Vivin, Equitable coloring of corona products of graphs, Adv. Appl. Discrete Math. 11 (2013) 103–120].
Źródło:
Discussiones Mathematicae Graph Theory; 2017, 37, 4; 1079-1094
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Better polynomial algorithms for scheduling unit-length jobswith bipartite incompatibility graphs on uniform machines
Autorzy:
Pikies, T.
Kubale, Marek
Powiązania:
https://bibliotekanauki.pl/articles/201958.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
approximation algorithm
graph coloring
incompatible job
polynomial algorithm
scheduling
uniform machine
unit-time jobs
algorytm aproksymacyjny
kolorowanie grafów
algorytm wielomianowy
planowanie
praca jednostkowa
Opis:
The goal of this paper is to explore and to provide tools for the investigation of the problems of unit-length scheduling of incompatible jobs on uniform machines. We present two new algorithms that are a significant improvement over the known algorithms. The first one is Algorithm 2 which is 2-approximate for the problem Qm|pj = 1, G = bisubquartic|Cmax. The second one is Algorithm 3 which is 4-approximate for the problem Qm|pj = 1, G = bisubquartic|ΣCj, where m ϵ {2, 3, 4}. The theory behind the proposed algorithms is based on the properties of 2-coloring with maximal coloring width, and on the properties of ideal machine, an abstract machine that we introduce in this paper.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 1; 31-36
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-8 z 8

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