Abstract
Computing a minimum vertex cover in graphs and hypergraphs is a well-studied optimizaton problem. While intractable in general, it is well known that on bipartite graphs, vertex cover is polynomial time solvable. In this work, we study the natural extension of bipartite vertex cover to hypergraphs, namely finding a small vertex cover in k-uniform k-partite hypergraphs, when the k-partition is given as input. For this problem Lovász [16] gave a \(\frac{k}{2}\) factor LP rounding based approximation, and a matching \(\left(\frac{k}{2} - o(1)\right)\) integrality gap instance was constructed by Aharoni et al. [1]. We prove the following results, which are the first strong hardness results for this problem (here ε> 0 is an arbitrary constant):
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NP-hardness of approximating within a factor of \(\left(\frac{k}{4} - \varepsilon\right)\), and
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Unique Games-hardness of approximating within a factor of \(\left(\frac{k}{2} - \varepsilon\right)\), showing optimality of Lovász’s algorithm under the Unique Games conjecture.
The NP-hardness result is based on a reduction from minimum vertex cover in r-uniform hypergraphs for which NP-hardness of approximating within r–1–ε was shown by Dinur et al. [5]. The Unique Games-hardness result is obtained by applying the recent results of Kumar et al. [15], with a slight modification, to the LP integrality gap due to Aharoni et al. [1]. The modification is to ensure that the reduction preserves the desired structural properties of the hypergraph.
Research supported in part by a Packard Fellowship and US-Israel BSF-2008293.
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References
Aharoni, R., Holzman, R., Krivelevich, M.: On a theorem of Lovász on covers in r-partite hypergraphs. Combinatorica 16(2), 149–174 (1996)
Austrin, P., Mossel, E.: Approximation resistant predicates from pairwise independence. In: IEEE Conference on Computational Complexity, pp. 249–258 (2008)
Bansal, N., Khot, S.: Inapproximability of hypergraph vertex cover and applications to scheduling problems. In: Proceedings of ICALP (July 2009)
Dinur, I., Guruswami, V., Khot, S.: Vertex cover on k-uniform hypergraphs is hard to approximate within factor (k-3-ε). ECCC Technical Report TR02-027 (2002)
Dinur, I., Guruswami, V., Khot, S., Regev, O.: A new multilayered PCP and the hardness of hypergraph vertex cover. In: Proc. 35th ACM STOC, pp. 595–601 (2003)
Dinur, I., Safra, S.: The importance of being biased. In: Proc. 34th ACM STOC, pp. 33–42 (2002)
Feder, T., Motwani, R., O’Callaghan, L., Panigrahy, R., Thomas, D.: Online distributed predicate evaluation. Technical Report, Stanford University (2003)
Gottlob, G., Senellart, P.: Schema mapping discovery from data instances. J. ACM 57(2) (January 2010)
Halperin, E.: Improved approximation algorithms for the vertex cover problem in graphs and hypergraphs. SIAM J. Comput. 31(5), 1608–1623 (2002)
Holmerin, J.: Improved inapproximability results for vertex cover on k -uniform hypergraphs. In: Widmayer, P., Triguero, F., Morales, R., Hennessy, M., Eidenbenz, S., Conejo, R. (eds.) ICALP 2002. LNCS, vol. 2380, pp. 1005–1016. Springer, Heidelberg (2002)
Ilie, L., Solis-Oba, R., Yu, S.: Reducing the size of NFAs by using equivalences and preorders. In: Apostolico, A., Crochemore, M., Park, K. (eds.) CPM 2005. LNCS, vol. 3537, pp. 310–321. Springer, Heidelberg (2005)
Khot, S.: On the power of unique 2-prover 1-round games. In: Proc. 34th ACM STOC, pp. 767–775 (2002)
Khot, S., Kindler, G., Mossel, E., O’Donnell, R.: Optimal inapproximability results for MAX-CUT and other 2-variable CSPs?. SIAM J. Comput. 37(1), 319–357 (2007)
Khot, S., Regev, O.: Vertex cover might be hard to approximate to within 2-epsilon. J. Comput. Syst. Sci. 74(3), 335–349 (2008)
Kumar, A., Manokaran, R., Tulsiani, M., Vishnoi, N.K.: On the optimality of a class of LP-based algorithms (2009) (manuscript)
Lovász, L.: On minimax theorems of combinatorics. Doctoral Thesis, Mathematiki Lapok 26, 209–264 (1975)
Manokaran, R., Naor, J., Raghavendra, P., Schwartz, R.: SDP gaps and UGC hardness for multiway cut, 0-extension, and metric labeling. In: Proc. 40th ACM STOC, pp. 11–20 (2008)
Mossel, E.: Gaussian bounds for noise correlation of functions and tight analysis of long codes. In: Proc. 49th IEEE FOCS, pp. 156–165 (2008)
Raghavendra, P.: Optimal algorithms and inapproximability results for every CSP? In: Proc. 40th ACM STOC, pp. 245–254 (2008)
Samorodnitsky, A., Trevisan, L.: Gowers uniformity, influence of variables, and PCPs. SIAM J. Comput. 39(1), 323–360 (2009)
Trevisan, L.: Non-approximability results for optimization problems on bounded degree instances. In: Proc. 33rd ACM STOC, pp. 453–461 (2001)
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Guruswami, V., Saket, R. (2010). On the Inapproximability of Vertex Cover on k-Partite k-Uniform Hypergraphs. In: Abramsky, S., Gavoille, C., Kirchner, C., Meyer auf der Heide, F., Spirakis, P.G. (eds) Automata, Languages and Programming. ICALP 2010. Lecture Notes in Computer Science, vol 6198. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-14165-2_31
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