Results 1  10
of
10
A Structural View on Parameterizing Problems: Distance from Triviality
 In First International Workshop on Parameterized and Exact Computation, IWPEC 2004, LNCS Proceedings
, 2004
"... Based on a series of known and new examples, we propose the generalized setting of "distance from triviality" measurement as a reasonable and prospective way of determining useful structural problem parameters in analyzing computationally hard problems. The underlying idea is to consid ..."
Abstract

Cited by 25 (12 self)
 Add to MetaCart
Based on a series of known and new examples, we propose the generalized setting of "distance from triviality" measurement as a reasonable and prospective way of determining useful structural problem parameters in analyzing computationally hard problems. The underlying idea is to consider tractable special cases of generally hard problems and to introduce parameters that measure the distance from these special cases. In this paper we present several case studies of distance from triviality parameterizations (concerning Clique, Power Dominating Set, Set Cover, and Longest Common Subsequence) that exhibit the versatility of this approach to develop important new views for computational complexity analysis.
Tree decompositions of graphs: Saving memory in dynamic programming
 CTW 2004: CologneTwente Workshop on Graphs and Combinatorial Optimization, Villa Vigoni (CO
, 2004
"... We propose a simple and effective heuristic to save memory in dynamic programming on tree decompositions when solving graph optimization problems. The introduced “anchor technique ” is based on a treelike set covering problem. We substantiate our findings by experimental results. Our strategy has n ..."
Abstract

Cited by 9 (2 self)
 Add to MetaCart
(Show Context)
We propose a simple and effective heuristic to save memory in dynamic programming on tree decompositions when solving graph optimization problems. The introduced “anchor technique ” is based on a treelike set covering problem. We substantiate our findings by experimental results. Our strategy has negligible computational overhead concerning running time but achieves memory savings for nice tree decompositions and path decompositions between 60 % and 98%.
Complexity and exact algorithms for multicut
 In: SOFSEM
"... Abstract. The Multicut problem is defined as: given an undirected graph and a collection of pairs of terminal vertices, find a minimum set of edges or vertices whose removal disconnects each pair. We mainly focus on the case of removing vertices, where we distinguish between allowing or disallowing ..."
Abstract

Cited by 8 (0 self)
 Add to MetaCart
Abstract. The Multicut problem is defined as: given an undirected graph and a collection of pairs of terminal vertices, find a minimum set of edges or vertices whose removal disconnects each pair. We mainly focus on the case of removing vertices, where we distinguish between allowing or disallowing the removal of terminal vertices. Complementing and refining previous results from the literature, we provide several NPcompleteness and (fixedparameter) tractability results for restricted classes of graphs such as trees, interval graphs, and graphs of bounded treewidth. 1
Computing Cooperative Solution Concepts in Coalitional Skill Games
"... We consider a simple model of cooperation among agents called Coalitional Skill Games (CSGs). This is a restricted form of coalitional games, where each agent has a set of skills that are required to complete various tasks. Each task requires a set of skills in order to be completed, and a coalition ..."
Abstract

Cited by 5 (0 self)
 Add to MetaCart
(Show Context)
We consider a simple model of cooperation among agents called Coalitional Skill Games (CSGs). This is a restricted form of coalitional games, where each agent has a set of skills that are required to complete various tasks. Each task requires a set of skills in order to be completed, and a coalition can accomplish the task only if the coalition’s agents cover the set of required skills for the task. The gain for a coalition depends only on the subset of tasks it can complete. We consider the computational complexity of several problems in CSGs, such as testing if an agent is a dummy or veto agent, computing the core and corerelated solution concepts, and computing power indices such as the Shapley value and Banzhaf power index. 1 Keywords: Coalitional game theory, Core, Power Indices
The Complexity of Weighted Counting for Acyclic Conjunctive Queries
, 2012
"... This paper is a study of weighted counting of the solutions of acyclic conjunctive queries (ACQ). The unweighted quantifier free version of this problem is known to be tractable (for combined complexity), but it is also known that introducing even a single quantified variable makes it #Phard. We fi ..."
Abstract

Cited by 4 (3 self)
 Add to MetaCart
(Show Context)
This paper is a study of weighted counting of the solutions of acyclic conjunctive queries (ACQ). The unweighted quantifier free version of this problem is known to be tractable (for combined complexity), but it is also known that introducing even a single quantified variable makes it #Phard. We first show that weighted counting for quantifierfree ACQ is still tractable and that even minimalistic extensions of the problem lead to hard cases. We then introduce a new parameter for quantified queries that permits to isolate a large island of tractability. We show that, up to a standard assumption from parameterized complexity, this parameter fully characterizes tractable subclasses for counting weighted solutions of ACQ queries. Thus we completely determines the tractability frontier for weighted counting for ACQ.
Minimum membership set covering and the consecutive ones property
 In Proc. 10th SWAT, volume 4059 of LNCS
, 2006
"... Abstract. The Minimum Membership Set Cover problem has recently been introduced and studied in the context of interference reduction in cellular networks. It has been proven to be notoriously hard in several aspects. Here, we investigate how natural generalizations and variations of this problem beh ..."
Abstract

Cited by 3 (1 self)
 Add to MetaCart
(Show Context)
Abstract. The Minimum Membership Set Cover problem has recently been introduced and studied in the context of interference reduction in cellular networks. It has been proven to be notoriously hard in several aspects. Here, we investigate how natural generalizations and variations of this problem behave in terms of the consecutive ones property: While it is wellknown that classical set covering problems become polynomialtime solvable when restricted to instances obeying the consecutive ones property, we experience a significantly more intricate complexity behavior in the case of Minimum Membership Set Cover. We provide polynomialtime solvability, NPcompleteness, and approximability results for various cases here. In addition, a number of interesting challenges for future research is exhibited. 1
Efficient Derivation of Numerical Dependencies
"... Numerical dependencies (NDs) are database constraints that limit the number of distinct Yvalues that can appear together with any Xvalue, where both X and Y are sets of attributes in a relation schema. While it is known that NDs are not finitely axiomatizable, there is no study on how to efficient ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
Numerical dependencies (NDs) are database constraints that limit the number of distinct Yvalues that can appear together with any Xvalue, where both X and Y are sets of attributes in a relation schema. While it is known that NDs are not finitely axiomatizable, there is no study on how to efficiently derive NDs using a set of sound (yet necessarily incomplete) rules. In this paper, after proving that solving the entailment problem for NDs using the chase procedure has exponential space complexity, we show that, given a set of inference rules similar to those used for functional dependencies, the membership problem for NDs is NPhard. We then provide a graphbased characterization of NDs, which is exploited to design an efficient branch & bound algorithm for ND derivation. Our algorithm adopts several optimization strategies that provide considerable speedup over a naïve approach, as confirmed by the results of extensive tests we made for efficiency and effectiveness using six different datasets.
Treewidth reduction for the parameterized Multicut problem
, 2010
"... The parameterized Multicut problem consists in deciding, given a graph, a set of requests (i.e. pairs of vertices) and an integer k, whether there exists a set of k edges which disconnects the two endpoints of each request. Determining whether Multicut is FixedParameter Tractable with respect to k ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
(Show Context)
The parameterized Multicut problem consists in deciding, given a graph, a set of requests (i.e. pairs of vertices) and an integer k, whether there exists a set of k edges which disconnects the two endpoints of each request. Determining whether Multicut is FixedParameter Tractable with respect to k is one of the most important open question in parameterized complexity [5]. We show that Multicut reduces to instances of treewidth bounded in k. To that aim, we establish new reduction rules that apply to arbitrary instances of Multicut. Based on graph separability properties, these rules identify an irrelevant request that can be safely removed. As a main consequence, these rules imply that the degree of the request graph of any instance is bounded by a function of k. We prove that when the input graph has a large clique minor or a large grid minor, then we can remove an irrelevant request or contract an edge.
Formation Doctorale: Informatique
"... et de Microélectronique de Montpellier pour ..."
(Show Context)
SEE PROFILE
"... Directwrite embedded waveguides and integrated optics in bulk glass by femosecond laser pulses ..."
Abstract
 Add to MetaCart
Directwrite embedded waveguides and integrated optics in bulk glass by femosecond laser pulses