Abstract
Path cover is a well-known intractable problem that finds a minimum number of vertex disjoint paths in a given graph to cover all the vertices. We show that a variant, in which the objective is to minimize the number of length-0 paths, is polynomial-time solvable. We further show that another variant, to minimize the total number of length-0 and length-1 paths, is also polynomial-time solvable. Both variants find applications in approximating the two-machine flow-shop scheduling problem in which job processing has constraints that are formulated as a conflict graph. For the unit jobs, we present a 4/3-approximation for the scheduling problem with an arbitrary conflict graph, based on the exact algorithm for the above second variant of the path cover problem. For arbitrary jobs where the conflict graph is the union of two disjoint cliques, we present a simple 3/2-approximation algorithm.
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References
Asdre K, Nikolopoulos SD (2007) A linear-time algorithm for the \(k\)-fixed-endpoint path cover problem on cographs. Networks 50:231–240
Asdre K, Nikolopoulos SD (2010) A polynomial solution to the \(k\)-fixed-endpoint path cover problem on proper interval graphs. Theor Comput Sci 411:967–975
Baker BS, Coffman EG (1996) Mutual exclusion scheduling. Theor Comput Sci 162:225–243
Bendraouche M, Boudhar M (2012) Scheduling jobs on identical machines with agreement graph. Comput Oper Res 39:382–390
Bendraouche M, Boudhar M (2016) Scheduling with agreements: new results. Int J Prod Res 54:3508–3522
Błażewicz J, Kubiak W, Szwarcfiter J (1988) Scheduling unit - time tasks on flow - shops under resource constraints. Ann Oper Res 16:255–266
Blazewicz J, Lenstra JK, Rinnooy Kan AHG (1983) Scheduling subject to resource constraints: classification and complexity. Discret Appl Math 5:11–24
Bodlaender HL, Jansen K (1995) Restrictions of graph partition problems. Part I. Theor Comput Sci 148:93–109
Cai Y, Chen G, Chen Y, Goebel R, Lin G, Liu L, Zhang A (2018) Approximation algorithms for two-machine flow-shop scheduling with a conflict graph. In: Proceedings of the 24th international computing and combinatorics conference (COCOON 2018), LNCS 10976, pp 205–217
Chen B, Glass CA, Potts CN, Strusevich VA (1996) A new heuristic for three-machine flow shop scheduling. Oper Res 44:891–898
Even G, Halldórsson MM, Kaplan L, Ron D (2009) Scheduling with conflicts: online and offline algorithms. J Schedul 12:199–224
Gabow HN (1983) An efficient reduction technique for degree-constrained subgraph and bidirected network flow problems. In: Proceedings of the 15th annual ACM symposium on theory of computing (STOC’83), pp 448–456
Garey MR, Graham RL (1975) Bounds for multiprocessor scheduling with resource constraints. SIAM J Comput 4:187–200
Garey MR, Johnson DS (1975) Complexity results for multiprocessor scheduling under resource constraints. SIAM J Comput 4:397–411
Garey MR, Johnson DS (1979) Computers and intractability: a guide to the theory of NP-completeness. W. H. Freeman and Company, San Francisco
Garey MR, Johnson DS, Sethi R (1976) The complexity of flowshop and jobshop scheduling. Math Oper Res 1:117–129
Garey MR, Johnson DS, Tarjan RE (1976) The planar Hamiltonian circuit problem is NP-complete. SIAM J Comput 5:704–714
Golumbic MC (2004) Algorithmic graph theory and perfect graphs. Elsevier, Amsterdam
Gómez R, Wakabayashi Y (2020) Nontrivial path covers of graphs: existence, minimization and maximization. J Combin Optim 39:437–456
Gonzalez T, Sahni S (1978) Flowshop and jobshop schedules: complexity and approximation. Oper Res 26:36–52
Graham RL, Lawler EL, Lenstra JK, Rinnooy Kan AHG (1979) Optimization and approximation in deterministic sequencing and scheduling: a survey. Ann Discret Math 5:287–326
Hall LA (1998) Approximability of flow shop scheduling. Math Program 82:175–190
Halldórsson MM, Kortsarz G, Proskurowski A, Salman R, Shachnai H, Telle JA (2003) Multicoloring trees. Inf Comput 180:113–129
Johnson SM (1954) Optimal two- and three-machine production schedules with setup times included. Naval Res Logist 1:61–68
Müller H (1996) Hamiltonian circuits in chordal bipartite graphs. Discret Math 156:291–298
Pao LL, Hong CH (2008) The two-equal-disjoint path cover problem of matching composition network. Inf Process Lett 107:18–23
Rizzi R, Tomescu AI, Mäkinen V (2014) On the complexity of minimum path cover with subpath constraints for multi-assembly. BMC Bioinform 15:S5
Röck H (1983) Scheduling unit task shops with resource constraints and excess usage costs. Technical Report, Fachbereich Informatik, Technical University of Berlin, Berlin
Röck H (1984) Some new results in flow shop scheduling. Zeitschrift für Oper Res 28:1–16
Süral H, Kondakci S, Erkip N (1992) Scheduling unit-time tasks in renewable resource constrained flowshops. Zeitschrift für Oper Res 36:497–516
Tellache NEH, Boudhar M (2017) Two-machine flow shop problem with unit-time operations and conflict graph. Int J Prod Res 55:1664–1679
Tellache NEH, Boudhar M (2018) Flow shop scheduling problem with conflict graphs. Ann Oper Res 261:339–363
Williamson DP, Hall LA, Hoogeveen JA, Hurkens CAJ, Lenstra JK, Sevastianov SV, Shmoys DB (1997) Short shop schedules. Oper Res 45:288–294
Acknowledgements
Y. Chen, G. Chen, and A. Zhang are supported by the NSFC Grants 11771114, 11971139 and the Zhejiang Provincial NSFC Grant LY21A010014; Y. Chen and A. Zhang are also supported by the China Scholarship Council Grants 201508330054 and 201908330090, respectively. R. Goebel, G. Lin, and L. Liu are supported by NSERC Canada; L. Liu is also supported by the Fundamental Research Funds for the Central Universities (Grant No. 20720160035) and the China Scholarship Council Grant No. 201706315073.
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An extended abstract appears in Proceedings of COCOON 2018 Cai et al. (2018)
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Chen, Y., Cai, Y., Liu, L. et al. Path cover with minimum nontrivial paths and its application in two-machine flow-shop scheduling with a conflict graph. J Comb Optim 43, 571–588 (2022). https://doi.org/10.1007/s10878-021-00793-3
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DOI: https://doi.org/10.1007/s10878-021-00793-3