Ralf Thöle

dblp:17/6022 · DBLP profile ↗
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4ranked-venue papers
0as first author
0since 2021 · last 2010
—ORCID · none

Domains — the database's venue-derived domains; a paper can count in several

Theory of computation · 3Applied, interdisciplinary, general and emerging computing · 1

Expertise — from the expertise taxonomy: the topics of the expert's papers under the CCF categories. A weight counts papers with recency: 1 for a paper about the topic, 0.3 when the topic is its context, halved every five years.

Theoretical computer science
2 papers
Approximation and online algorithms · 64% Mathematical optimization · 36%

Topics — the 2 heaviest of 2, each with the papers that count most for it

TopicWeightPapersLastEvidence papers
Approximation and online algorithms
scheduling approximation
0.222010
Approximation Algorithms for Scheduling Parallel Jobs · SIAM J. Comput. 2010
Approximation Algorithms for Scheduling Parallel Jobs: Breaking the Approximation Ratio of 2 · ICALP (1) 2008
Mathematical optimization
scheduling
0.112010
Approximation Algorithms for Scheduling Parallel Jobs · SIAM J. Comput. 2010

Methods — techniques the papers use, named apart from their topics

polynomial-time approximation scheme · 0.1approximation algorithm · 0.1
YearPublicationVenuePosition
2010 Approximation Algorithms for Scheduling Parallel Jobs
abstract
In this paper we study variants of the nonpreemptive parallel job scheduling problem in which the number of machines is polynomially bounded in the number of jobs. For this problem we show that a schedule with length at most $(1+\varepsilon)\,\mathrm{OPT}$ can be calculated in polynomial time. Unless $P=NP$, this is the best possible result (in the sense of approximation ratio), since the problem is strongly NP-hard. For the case where all jobs must be allotted to a subset of consecutive machines, a schedule with length at most $(1.5+\varepsilon)\,\mathrm{OPT}$ can be calculated in polynomial time. The previously best known results are algorithms with absolute approximation ratio 2. Furthermore, we extend both algorithms to the case of malleable jobs with the same approximation ratios.
Klaus Jansen, Ralf Thöle
SIAM J. Comput.2
2008 Approximation Algorithms for Scheduling Parallel Jobs: Breaking the Approximation Ratio of 2
Klaus Jansen, Ralf Thöle
ICALP (1)2
2008 Approximation Algorithms for 3D Orthogonal Knapsack
abstract
We study non-overlapping axis-parallel packings of 3D boxes with profits into a dedicated bigger box where rotation is either forbidden or permitted, and we wish to maximize the total profit. Since this optimization problem is NP-hard, we focus on approximation algorithms. We obtain fast and simple algorithms for the non-rotational scenario with approximation ratios 9 + ϵ and 8 + ϵ, as well as an algorithm with approximation ratio 7 + ϵ that uses more sophisticated techniques; these are the smallest approximation ratios known for this problem. Furthermore, we show how the used techniques can be adapted to the case where rotation by 90° either around the z -axis or around all axes is permitted, where we obtain algorithms with approximation ratios 6 + ϵ and 5 + ϵ, respectively. Finally our methods yield a 3D generalization of a packability criterion and a strip packing algorithm with absolute approximation ratio 29/4, improving the previously best known result of 45/4.
Florian Diedrich, Rolf Harren, Klaus Jansen, Ralf Thöle, Henning Thomas
J. Comput. Sci. Technol.4
2007 Approximation Algorithms for 3D Orthogonal Knapsack
Florian Diedrich, Rolf Harren, Klaus Jansen, Ralf Thöle, Henning Thomas
TAMC4