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- Martin R. Ehmsen, Kim S. Larsen
- SWAT
- 2010

Unit Clustering is the problem of dividing a set of points from a metric space into a minimal number of subsets such that the points in each subset are enclosable by a unit ball. We continue work initiated by Chan and Zarrabi-Zadeh on determining the competitive ratio of the online version of this problem. For the one-dimensional case, we develop a… (More)

- Joan Boyar, Martin R. Ehmsen, Kim S. Larsen
- WAOA
- 2006

The paging algorithm LRU-2 was proposed for use in database disk buffering and shown experimentally to perform better than LRU [O'Neil, O'Neil, and Weikum, 1993]. We compare LRU-2 and LRU theoretically, using both the standard competitive analysis and the newer relative worst order analysis. The competitive ratio for LRU-2 is shown to be 2k for cache size… (More)

- Reza Dorrigiv, Martin R. Ehmsen, Alejandro López-Ortiz
- Algorithmica
- 2009

It is well-established that input sequences for paging and list update have locality of reference. In this paper we analyze the performance of algorithms for these problems in terms of the amount of locality in the input sequence. We define a measure for locality that is based on Denning’s working set model and express the performance of well known… (More)

- Martin R. Ehmsen, Jens S. Kohrt, Kim S. Larsen
- Algorithmica
- 2010

Relative worst order analysis is a supplement or alternative to competitive analysis which has been shown to give results more in accordance with observed behavior of online algorithms for a range of different online problems. The contribution of this paper is twofold. As the first contribution, it adds the static list accessing problem to the collection of… (More)

- Martin R. Ehmsen, Lene M. Favrholdt, Jens S. Kohrt, Rodica Mihai
- Theor. Comput. Sci.
- 2008

We study the performance of the algorithms First-Fit and Next-Fit for two online edge coloring problems. In the min-coloring problem, all edges must be colored using as few colors as possible. In the max-coloring problem, a fixed number of colors is given, and as many edges as possible should be colored. Previous analysis using the competitive ratio has not… (More)

- Joan Boyar, Martin R. Ehmsen, Jens S. Kohrt, Kim S. Larsen
- Acta Inf.
- 2010

The paging algorithm Least Recently Used Second Last Request (LRU-2) was proposed for use in database disk buffering and shown experimentally to perform better than Least Recently Used (LRU). We compare LRU-2 and LRU theoretically, using both the standard competitive analysis and the newer relative worst order analysis. The competitive ratio for LRU-2 is… (More)

The paging algorithm LRU-K was proposed for use in database disk buffering and shown experimentally to perform better than LRU [19]. In [7], relative worst order analysis [6] was extended and a new paging algorithm RLRU was introduced, which was shown to outperform LRU using the relative worst order ratio. We combine LRU-K and RLRU and introduce the paging… (More)

- Martin R. Ehmsen, Kim S. Larsen
- Int. J. Found. Comput. Sci.
- 2013

Inspired by a real-life application, we investigate the computationally hard problem of extending a precoloring of an interval graph to a proper coloring under some bound on the number of available colors. We are interested in quickly determining whether or not such an extension exists on instances occurring in practice in connection with campsite bookings… (More)

The paging algorithm Least Recently Used Second-to-Last Request (LRU-2) was proposed for use in database disk buffering and shown experimentally to perform better than Least Recently Used (LRU). We compare LRU-2 and LRU theoretically, using both the standard competitive analysis and the newer relative worst order analysis. The competitive ratio for LRU-2 is… (More)

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