Seminář z aproximačních a online algoritmů
Seminar on Approximation and Online Algorithms

Andreas Emil Feldmann, Petr Kolman, Jiří Sgall

Doba a místo konání [Time and place]

Seminář se koná v pátek od 10:40 v S10.

Oznámení o seminářích se distribuuje pomocí mailing listu, do kterého se můžete zapsat na adrese
You can subscribe to the mailing list with the seminar anouncement at

Kontakt, tel. 951 554 372;, tel. 951 554 155;, tel. 951 554 293.

Nejbližší program semináře [Next program]

23. 2. 2018 (pátek [Friday], 10:40, MFF UK Malá Strana S10)

Nikhil Bansal, Marek Elias, Grigorios Koumoutsos, and Jesper Nederlof: Competitive Algorithms for Generalized k-Server in Uniform Metrics. SODA 2018. Also
(presented by Jakub Sosnovec)

Abstract: The generalized k-server problem is a far-reaching extension of the k-server problem with several applications. Here, each server si lies in its own metric space Mi. A request is a k-tuple r = (r1, r2, …, rk) and to serve it, we need to move some server si to the point riMi, and the goal is to minimize the total distance traveled by the servers. Despite much work, no f(k)-competitive algorithm is known for the problem for k>2 servers, even for special cases such as uniform metrics and lines.

Here, we consider the problem in uniform metrics and give the first f(k)-competitive algorithms for general k. In particular, we obtain deterministic and randomized algorithms with competitive ratio k·2k and O(k3 log k) respectively. Our deterministic bound is based on a novel application of the polynomial method to online algorithms, and essentially matches the long-known lower bound of 2k–1. We also give a 22O(k)-competitive deterministic algorithm for weighted uniform metrics, which also essentially matches the recent doubly exponential lower bound for the problem. 

Předběžný další program [Preliminary future program]

Martin Skutella: A Note on the Ring Loading Problem. SIAM J. Discrete Math., 30(1), 327-342. 2016.
(presented by Lukáš Folwarczný)

Další články pro ZS 2017 [More papers proposed for this semester]

Euiwoong Lee: Improved Hardness for Cut, Interdiction, and Firefighter Problems. ICALP 2017. Best Student Paper. Also

Andreas Wiese: A (1+eps)-approximation for Unsplittable Flow on a Path in fixed-parameter running time. ICALP 2017.

Parinya Chalermsook, Marek Cygan, Guy Kortsarz, Bundit Laekhanukit, Pasin Manurangsi, Danupon Nanongkai, Luca Trevisan: From Gap-ETH to FPT-Inapproximability: Clique, Dominating Set, and More. FOCS 2017. Also

Michael Lampis: Parameterized Approximation Schemes using Graph Widths. ICALP 2014. Also

Alice Paul, Daniel Freund, Aaron Ferber, David Shmoys and David Williamson: Prize-Collecting TSP with a Budget Constraint. ESA 2017.

Samozřejmě, jako vždy, jsou vítany jsou i další náměty, zejména pak prezentace vlastních výsledků účastníků semináře.

Další články, o kterých jsme uvažovali, zbylé z minulého semestru atd.
[Additional proposed papers, leftovers from the last semester]

Klaus Jansen and Lars Rohwedder: On the Configuration-LP of the Restricted Assignment Problem. SODA 2017: 2670-2678, also

Martijn van Ee, Leo van Iersel, Teun Janssen, René Sitters: A priori TSP in the Scenario Model. WAOA 2016: 183-196.

Alantha Newman, Heiko Röglin, and Johanna Seif: The Alternating Stock Size Problem and the Gasoline Puzzle. ESA 2016. Also

János Balogh, József Békési, György Dósa, Leah Epstein, Asaf Levin: Online bin packing with cardinality constraints resolved. At

Harald Räcke: Optimal hierarchical decompositions for congestion minimization in networks. STOC 2008:255-264. Also here.

Jittat Fakcheroenphol, Kunal Talwar and Satish Rao: A tight bound on approximating arbitrary metrics by tree metrics. STOC 2003, J. Comput. Syst. Sci. 69(3): 485-497 (2004).

Předchozí program semináře [Past program]