The paper addresses the problem of enumerating minimal siphons in an ordinary Petri net. The algorithms developed in this work recursively use a problem partitioning procedure to reduce the original search problem to ...
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The paper addresses the problem of enumerating minimal siphons in an ordinary Petri net. The algorithms developed in this work recursively use a problem partitioning procedure to reduce the original search problem to multiple simpler search subproblems. Each subproblem has specific additional place constraints with respect to the original problem. Some results on algorithm correctness, convergence, and computational complexity are provided, as well as an experimental evaluation of performance. The algorithms can be applied to enumerate minimal, place-minimal siphons, or even siphons that are minimal with respect to given subsets of places.
Submodular functions are powerful tools to model and solve either to optimality or approximately many operational research problems including problems defined on graphs. After reviewing some long-standing theoretical ...
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Submodular functions are powerful tools to model and solve either to optimality or approximately many operational research problems including problems defined on graphs. After reviewing some long-standing theoretical results about the structure of local and global maxima of submodular functions, Cherenin's selection rules and his Dichotomy Algorithm, we revise the above mentioned theory and show that our revision is useful for creating new non-binary branching algorithms and finding either approximation solutions with guaranteed accuracy or exact ones. (C) 2008 Elsevier B.V. All rights reserved.
An irreducible triangulation is a plane graph such that its outer face is a quadrangle, every inner face is a triangle, and it has no separating triangle. Let T be an irreducible triangulation with n vertices. A recta...
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An irreducible triangulation is a plane graph such that its outer face is a quadrangle, every inner face is a triangle, and it has no separating triangle. Let T be an irreducible triangulation with n vertices. A rectangular dual R of T is a dissection of a rectangle into (small) rectangles such that (1) each rectangle of R corresponds to a vertex of T , and (2) two rectangles of R are adjacent if the two corresponding vertices of T are adjacent. Finding a rectangular dual of a given graph has an application on cartograms and VLSI floor-planning. In this paper, we consider the problem of enumerating all the rectangular duals of a given irreducible triangulation. It is known that the set of rectangular duals of an irreducible triangulation T one-to-one corresponds to the set of transversal edge-partitions of T . Hence, in this paper, we design an enumeration algorithm of all the transversal edge-partitions of an irreducible triangulation with n vertices. The proposed algorithm enumerates them in O ( n )-delay and O ( n 2 )-space after O ( n log n )-time preprocessing. (c) 2024 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Due to the sheer size of real-world networks, delay and space have become quite relevant measures of the cost of enumerating patterns for network analytics. This paper presents efficient algorithms for listing maximal...
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Due to the sheer size of real-world networks, delay and space have become quite relevant measures of the cost of enumerating patterns for network analytics. This paper presents efficient algorithms for listing maximal cliques in undirected graphs, providing the first sublinear-space bounds with guaranteed delay per solution.
The number of minimal dominating sets that a graph on n vertices can have is known to be at most 1.7159(n). This upper bound might not be tight, since no examples of graphs with 1.5705(n) or more minimal dominating se...
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The number of minimal dominating sets that a graph on n vertices can have is known to be at most 1.7159(n). This upper bound might not be tight, since no examples of graphs with 1.5705(n) or more minimal dominating sets are known. For several classes of graphs, we substantially improve the upper bound on the number of minimal dominating sets. At the same time, we give algorithms for enumerating all minimal dominating sets, where the running time of each algorithm is within a polynomial factor of the proved upper bound for the graph class in question. In several cases, we provide examples of graphs containing the maximum possible number of minimal dominating sets for graphs in that class, thereby showing the corresponding upper bounds to be tight. (C) 2013 Elsevier B.V. All rights reserved.
作者:
Meeks, KittyUniv Glasgow
Sch Comp Sci Sir Alwyn Williams Bldg Glasgow G12 8RZ Lanark Scotland
Many combinatorial problems involve determining whether a universe of n elements contains a witness consisting of k elements which have some specified property. In this paper we investigate the relationship between th...
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Many combinatorial problems involve determining whether a universe of n elements contains a witness consisting of k elements which have some specified property. In this paper we investigate the relationship between the decision and enumeration versions of such problems: efficient methods are known for transforming a decision algorithm into a search procedure that finds a single witness, but even finding a second witness is not so straightforward in general. We show that, if the decision version of the problem can be solved in time f(k) . poly(n), there is a randomised algorithm which enumerates all witnesses in time e(k+o(k)) . f(k) . poly(n) . N, where N is the total number of witnesses. If the decision version of the problem is solved by a randomised algorithm which may return false negatives, then the same method allows us to output a list of witnesses in which any given witness will be included with high probability. The enumeration algorithm also gives rise to an efficient algorithm to count the total number of witnesses when this number is small.
We present a general framework to study enumeration algorithms for maximal cliques and maximal bicliques of a graph. Given a graph G, we introduce the notion of the transition graph T(G) whose vertices are maximal cli...
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We present a general framework to study enumeration algorithms for maximal cliques and maximal bicliques of a graph. Given a graph G, we introduce the notion of the transition graph T(G) whose vertices are maximal cliques of G and arcs are transitions between cliques. We show that T(G) is a strongly connected graph and characterize a rooted cover tree of T(G) which appears implicitly in [D.S. Johnson, M. Yannakakis, C.H. Papadimitriou, On generating all maximal independent sets, Information Processing Letters 27 (1988) 119-123;S. Tsukiyama, M. Ide, M. Aiyoshi, I. Shirawaka, A new algorithm for generating all the independent sets, SIAM journal on Computing 6 (1977) 505-517]. When G is a bipartite graph, we show that the Galois lattice of G is a partial graph of T(G) and we deduce that algorithms based on the Galois lattice are a particular search of T(G). Moreover, we show that algorithms in [G. Alexe, S. Alexe, Y. Crama, S. Foldes, P.L. Hammer, B. Simeone, Consensus algorithms for the generation of all maximal bicliques, Discrete Applied Mathematics 145 (1) (2004) 11-21: L Nourine, O. Raynaud, A fast algorithm for building lattices, Information Processing Letters 71 (1999) 199-204] generate maximal bicliques of a bipartite graph in O(n(2)) per maximal biclique, where n is the number of vertices in G. Finally, we show that under some specific numbering, the transition graph T(G) has a hamiltonian path for chordal and comparability graphs. (C) 2008 Elsevier B.V. All rights reserved.
Some of the most relevant document schemas used online, such as XML and JSON, have a nested format. In the past decade, the task of extracting data from nested documents over streams has become especially relevant. We...
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Some of the most relevant document schemas used online, such as XML and JSON, have a nested format. In the past decade, the task of extracting data from nested documents over streams has become especially relevant. We focus on the streaming evaluation of queries with outputs of varied sizes over nested documents. We model queries of this kind as Visibly Pushdown Annotators (VPAnn), a computational model that extends visibly pushdown automata with outputs and has the same expressive power as monadic second-order logic over nested documents. Since processing a document through a VPAnn can generate a massive number of results, we are interested in reading the input in a streaming fashion and enumerating the outputs one after another as efficiently as possible, namely, with constant delay. This article presents an algorithm that enumerates these elements with constant delay after processing the document stream in a single pass. Furthermore, we show that this algorithm is worst-case optimal in terms of update-time per symbol and memory usage.
We are given a set S of points in the Euclidean plane. We assume that S is in general position. A simple polygon P is a surrounding polygon of S if each vertex of P is a point in S and every point in S is either insid...
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We are given a set S of points in the Euclidean plane. We assume that S is in general position. A simple polygon P is a surrounding polygon of S if each vertex of P is a point in S and every point in S is either inside P or a vertex of P. In this paper, we present an enumeration algorithm of the surrounding polygons for a given point set. Our algorithm is based on reverse search by Avis and Fukuda and enumerates all the surrounding polygons in polynomial delay and quadratic space. It also provides the first space efficient method to generate all simple polygonizations on a given point set in exponential time. By relating these two problems we provide an upper bound on the number of surrounding polygons. (C) 2020 Elsevier B.V. All rights reserved.
An irredundant set of a hypergraph G = (V, H) is a subset S of its nodes such that removing any node from S decreases the number of hyperedges it intersects. The concept is deeply related to that of dominating sets, a...
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ISBN:
(数字)9783030250058
ISBN:
(纸本)9783030250041;9783030250058
An irredundant set of a hypergraph G = (V, H) is a subset S of its nodes such that removing any node from S decreases the number of hyperedges it intersects. The concept is deeply related to that of dominating sets, as the minimal dominating sets of a graph correspond exactly to the dominating sets which are also maximal irredundant sets. In this paper we propose an FPT-delay algorithm for listing maximal irredundant sets, whose delay is O(2(d)Delta(d+1)n(2)), where d is the degeneracy of the hypergraph and. the maximum node degree. As d <= Delta, we immediately obtain an algorithm with delay O(2(Delta)Delta(Delta+1)n(2)) that is FPT for bounded-degree hypergraphs. This result opens a gap between known bounds for this problem and those for listing minimal dominating sets in these classes of hypergraphs, as the known running times used to be the same, hinting at the idea that the latter may indeed be harder.
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