The Experts below are selected from a list of 35022 Experts worldwide ranked by ideXlab platform
Meirav Zehavi - One of the best experts on this subject based on the ideXlab platform.
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long Directed s t path fpt algorithm
Information Processing Letters, 2018Co-Authors: Fedor V Fomin, Daniel Lokshtanov, Fahad Panolan, Saket Saurabh, Meirav ZehaviAbstract:Abstract Given a digraph G, two vertices s , t ∈ V ( G ) and a non-negative integer k, the Long Directed ( s , t ) -Path problem asks whether G has a path of length at least k from s to t. We present a simple algorithm that solves Long Directed ( s , t ) -Path in time O ⋆ ( 4.884 k ) . This results also in an improvement upon the previous fastest algorithm for Long Directed Cycle .
Hacene Ouzia - One of the best experts on this subject based on the ideXlab platform.
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an efficient cutting plane algorithm for the minimum weighted elementary Directed Cycle problem in planar digraphs
Rairo-operations Research, 2016Co-Authors: Mamane Souley Ibrahim, Nelson Maculan, Hacene OuziaAbstract:In this paper, we study the efficiency (both theoretically and computationally) of a class of valid inequalities for the minimum weighted elementary Directed Cycle problem (MWEDCP) in planar digraphs with negative weight elementary Directed Cycles. These valid inequalities are called Cycle valid inequalities and are parametrized by an integer called inequality’s order. From a theoretical point of view, we prove that separating Cycle valid inequalities of order 1 in planar digraph can be done in polynomial time. From a computational point of view, we present a cutting plane algorithm featuring the efficiency of a lifted form of the Cycle valid inequalities of order 1. In addition to these lifted valid inequalities, our algorithm is also based on a mixed integer linear formulation of the MWEDCP. The computational results are carried out on randomly generated planar digraph instances of the MWEDCP. For all 29 instances considered, we obtain in average 26.47% gap improvement. Moreover, for some of our instances the strengthening process directly displays the optimal integer elementary Directed Cycle.
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an efficient cutting plane algorithm for the minimum weighted elementary Directed Cycle problem in planar digraphs
Rairo-operations Research, 2016Co-Authors: Mamane Souley Ibrahim, Nelson Maculan, Hacene OuziaAbstract:In this paper, we study the efficiency (both theoretically and computationally) of a class of valid inequalities for the minimum weighted elementary Directed Cycle problem (MWEDCP) in planar digraphs with negative weight elementary Directed Cycles. These valid inequalities are called Cycle valid inequalities and are parametrized by an integer called inequality’s order. From a theoretical point of view, we prove that separating Cycle valid inequalities of order 1 in planar digraph can be done in polynomial time. From a computational point of view, we present a cutting plane algorithm featuring the efficiency of a lifted form of the Cycle valid inequalities of order 1. In addition to these lifted valid inequalities, our algorithm is also based on a mixed integer linear formulation of the MWEDCP. The computational results are carried out on randomly generated planar digraph instances of the MWEDCP. For all 29 instances considered, we obtain in average 26.47% gap improvement. Moreover, for some of our instances the strengthening process directly displays the optimal integer elementary Directed Cycle.
Kowei Lih - One of the best experts on this subject based on the ideXlab platform.
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full orientability of the square of a Cycle
arXiv: Combinatorics, 2012Co-Authors: Weifan Wang, Kowei LihAbstract:Let D be an acyclic orientation of a simple graph G. An arc of D is called dependent if its reversal creates a Directed Cycle. Let d(D) denote the number of dependent arcs in D. Define m and M to be the minimum and the maximum number of d(D) over all acyclic orientations D of G. We call G fully orientable if G has an acyclic orientation with exactly k dependent arcs for every k satisfying m <= k <= M. In this paper, we prove that the square of a Cycle C_n of length n is fully orientable except n=6.
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on preserving full orientability of graphs
The Journal of Combinatorics, 2010Co-Authors: Hsinhao Lai, Kowei LihAbstract:Suppose that D is an acyclic orientation of the graph G. An arc of D is dependent if its reversal creates a Directed Cycle. Let d"m"i"n(G) (d"m"a"x(G)) denote the minimum (maximum) of the number of dependent arcs over all acyclic orientations of G. We call Gfully orientable if G has an acyclic orientation with exactly k dependent arcs for every k satisfying d"m"i"n(G)=
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full orientability of graphs with at most one dependent arc
Discrete Applied Mathematics, 2009Co-Authors: Hsinhao Lai, Kowei Lih, Lida TongAbstract:Suppose that D is an acyclic orientation of a graph G. An arc of D is dependent if its reversal creates a Directed Cycle. Let d"m"i"n(G) (d"m"a"x(G)) denote the minimum (maximum) of the number of dependent arcs over all acyclic orientations of G. We call Gfully orientable if G has an acyclic orientation with exactly d dependent arcs for every d satisfying d"m"i"n(G)=
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on fully orientability of 2 degenerate graphs
Information Processing Letters, 2008Co-Authors: Hsinhao Lai, Gerard J Chang, Kowei LihAbstract:Suppose that D is an acyclic orientation of the graph G. An arc of D is dependent if its reversal creates a Directed Cycle. Let d(D) denote the number of dependent arcs in D. Define d"m"i"n(G) (d"m"a"x(G)) to be the minimum (maximum) number of d(D) over all acyclic orientations D of G. We call G fully orientable if G has an acyclic orientation with exactly k dependent arcs for every k satisfying d"m"i"n(G)=
Fedor V Fomin - One of the best experts on this subject based on the ideXlab platform.
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long Directed s t path fpt algorithm
Information Processing Letters, 2018Co-Authors: Fedor V Fomin, Daniel Lokshtanov, Fahad Panolan, Saket Saurabh, Meirav ZehaviAbstract:Abstract Given a digraph G, two vertices s , t ∈ V ( G ) and a non-negative integer k, the Long Directed ( s , t ) -Path problem asks whether G has a path of length at least k from s to t. We present a simple algorithm that solves Long Directed ( s , t ) -Path in time O ⋆ ( 4.884 k ) . This results also in an improvement upon the previous fastest algorithm for Long Directed Cycle .
Mamane Souley Ibrahim - One of the best experts on this subject based on the ideXlab platform.
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an efficient cutting plane algorithm for the minimum weighted elementary Directed Cycle problem in planar digraphs
Rairo-operations Research, 2016Co-Authors: Mamane Souley Ibrahim, Nelson Maculan, Hacene OuziaAbstract:In this paper, we study the efficiency (both theoretically and computationally) of a class of valid inequalities for the minimum weighted elementary Directed Cycle problem (MWEDCP) in planar digraphs with negative weight elementary Directed Cycles. These valid inequalities are called Cycle valid inequalities and are parametrized by an integer called inequality’s order. From a theoretical point of view, we prove that separating Cycle valid inequalities of order 1 in planar digraph can be done in polynomial time. From a computational point of view, we present a cutting plane algorithm featuring the efficiency of a lifted form of the Cycle valid inequalities of order 1. In addition to these lifted valid inequalities, our algorithm is also based on a mixed integer linear formulation of the MWEDCP. The computational results are carried out on randomly generated planar digraph instances of the MWEDCP. For all 29 instances considered, we obtain in average 26.47% gap improvement. Moreover, for some of our instances the strengthening process directly displays the optimal integer elementary Directed Cycle.
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an efficient cutting plane algorithm for the minimum weighted elementary Directed Cycle problem in planar digraphs
Rairo-operations Research, 2016Co-Authors: Mamane Souley Ibrahim, Nelson Maculan, Hacene OuziaAbstract:In this paper, we study the efficiency (both theoretically and computationally) of a class of valid inequalities for the minimum weighted elementary Directed Cycle problem (MWEDCP) in planar digraphs with negative weight elementary Directed Cycles. These valid inequalities are called Cycle valid inequalities and are parametrized by an integer called inequality’s order. From a theoretical point of view, we prove that separating Cycle valid inequalities of order 1 in planar digraph can be done in polynomial time. From a computational point of view, we present a cutting plane algorithm featuring the efficiency of a lifted form of the Cycle valid inequalities of order 1. In addition to these lifted valid inequalities, our algorithm is also based on a mixed integer linear formulation of the MWEDCP. The computational results are carried out on randomly generated planar digraph instances of the MWEDCP. For all 29 instances considered, we obtain in average 26.47% gap improvement. Moreover, for some of our instances the strengthening process directly displays the optimal integer elementary Directed Cycle.