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| Content Provider | Society for Industrial and Applied Mathematics (SIAM) |
|---|---|
| Author | Chakrabarty, Deeparnab Panigrahi, Debmalya Ene, Alina Krishnaswamy, Ravishankar |
| Copyright Year | 2018 |
| Abstract | We present the first online algorithms for the nonuniform, multicommodity buy-at-bulk (MC-BB) network design problem. Our competitive ratios qualitatively match the best known approximation factors for the corresponding offline problems. In particular, we show (a) a polynomial time online algorithm with a polylogarithmic competitive ratio for the MC-BB problem in undirected edge-weighted graphs, (b) a quasi-polynomial time online algorithm with a polylogarithmic competitive ratio for the MC-BB problem in undirected node-weighted graphs, (c) for any fixed $\epsilon > 0$, a polynomial time online algorithm with a competitive ratio of $\tilde{O}\big(k^{\frac{1}{2}+\epsilon})$ (where $k$ is the number of demands, and the tilde hides polylog factors) for MC-BB in directed graphs, and (d) algorithms with matching competitive ratios for the prize-collecting variant of all the preceding problems. Prior to our work, a logarithmic competitive ratio was known for undirected, edge-weighted graphs only for the special case of uniform costs [B. Awerbuch and Y. Azar, FOCS, 1997, pp. 542--547], and a polylogarithmic-competitive algorithm was known for the edge-weighted single-sink problem [A. Meyerson, Procedings of SPAA, 2004, pp. 275--280]. We believe no online algorithm was known in the node-weighted and directed settings, even for uniform costs. Our main technical contribution is an online reduction theorem of MC-BB problems to their single-sink counterparts. We use the concept of junction-tree solutions from [C. Chekuri, M. T. Hajiaghayi, G. Kortsarz, and M. R. Salavatipour, Proceedings of FOCS, 2006, pp. 677--686], which play an important role in solving the offline versions of the problem via a greedy subroutine---an inherently offline procedure. We use just the existence of good junction-trees for our reduction. |
| Sponsorship | Google. Duke University |
| Starting Page | 1505 |
| Ending Page | 1528 |
| Page Count | 24 |
| File Format | |
| ISSN | 00975397 |
| DOI | 10.1137/16M1117317 |
| e-ISSN | 10957111 |
| Journal | SIAM Journal on Computing (SMJCAT) |
| Issue Number | 4 |
| Volume Number | 47 |
| Language | English |
| Publisher | Society for Industrial and Applied Mathematics |
| Publisher Date | 2018-07-26 |
| Access Restriction | Subscribed |
| Subject Keyword | algorithms Online algorithms Approximation methods and heuristics Approximation algorithms approximation algorithms network design online algorithms |
| Content Type | Text |
| Resource Type | Article |
| Subject | Mathematics Computer Science |
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