We consider the combinatorial RNA Design problem, a minimal instance of RNA design where one must produce an RNA sequence that adopts a given secondary structure as its minimal free-energy structure. We consider two f...
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We consider the combinatorial RNA Design problem, a minimal instance of RNA design where one must produce an RNA sequence that adopts a given secondary structure as its minimal free-energy structure. We consider two free-energy models where the contributions of base pairs are additive and independent: the purely combinatorial Watson-Crick model, which only allows equally-contributing A-U and C-G base pairs, and the real-valued Nussinov-Jacobson model, which associates arbitrary energies to A-U, C-G and G-U base pairs. We first provide a complete characterization of designable structures using restricted alphabets and, in the four-letter alphabet, provide a complete characterization for designable structures without unpaired bases. When unpaired bases are allowed, we characterize extensive classes of (non-) designable structures, and prove the closure of the set of designable structures under the stutter operation. Membership of a given structure to any of the classes can be tested in Theta(n) time, including the generation of a solution sequence for positive instances. Finally, we consider a structure-approximating relaxation of the design, and provide a Theta(n) algorithm which, given a structure S that avoids two trivially non-designable motifs, transforms S into a designable structure constructively by adding at most one base-pair to each of its stems.
In 1998, Hu and Liu developed a strongly polynomial algorithm for solving the inverse arborescence problem that aims at minimally modifying a given cost-function on the edge-set of a digraph D so that an input spannin...
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In 1998, Hu and Liu developed a strongly polynomial algorithm for solving the inverse arborescence problem that aims at minimally modifying a given cost-function on the edge-set of a digraph D so that an input spanning arborescence of D becomes a cheapest one. In this note, we develop a conceptually simpler algorithm along with a new min-max formula for the minimum modification of the cost-function. The approach is based on a link to a min-max theorem and a simple (two-phase greedy) algorithm by the first author from 1979 concerning the primal optimization problem of finding a cheapest subgraph of a digraph that covers an intersecting family along with the corresponding dual optimization problem, as well. (C) 2021 The Author(s). Published by Elsevier B.V.
The problem is to modify the capacities of the arcs from a network so that a given feasible flow becomes a maximum flow and the maximum change of the capacities on arcs is minimum. A very fast O(m . log(n)) time compl...
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The problem is to modify the capacities of the arcs from a network so that a given feasible flow becomes a maximum flow and the maximum change of the capacities on arcs is minimum. A very fast O(m . log(n)) time complexity algorithm for solving this problem is presented, where m is the number of arcs and n is the number of nodes of the network. The case when both, lower and upper bounds of the flow can be modified so that the given feasible flow becomes a maximum flow is also discussed. The algorithm proposed can be adapted to solve this problem, too. The inverse minimum flow problem considering l(infinity) norm is also studied.
In this paper we study the 0-1 inverse maximum stable set problem, denoted by IS([0,1]). Given a graph and a fixed stable set, it is to delete the minimum number of vertices to make this stable set maximum ill the new...
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In this paper we study the 0-1 inverse maximum stable set problem, denoted by IS([0,1]). Given a graph and a fixed stable set, it is to delete the minimum number of vertices to make this stable set maximum ill the new graph. We also consider IS([0,1]) against a Specific algorithm such as Greedy and 2opt, aiming to delete the minimum number of vertices so that the algorithm selects the given stable set in the new graph;we denote them by IS([0,1],greedy) and IS([0,1],2opt), respectively. Firstly, we show that they are NIP-hard. even if the fixed stable set contains only one vertex. Secondly, we achieve an approximation ratio of 2 - circle minus(1/root log Delta) for IS([0,1],2opt). Thirdly, we study the tractability of IS([0,1]) for some classes of perfect graphs such as comparability, co-comparability and chordal graphs. Finally, we compare the hardness of IS([0,1]) and IS([0,1],2opt) for some other classes of graphs. (c) 2008 Published by Elsevier B.V.
Given a graph G and a positive integer K, the inverse chromatic number problem consists in modifying the graph as little as possible so that it admits a chromatic number not greater than K. In this paper, we focus on ...
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Given a graph G and a positive integer K, the inverse chromatic number problem consists in modifying the graph as little as possible so that it admits a chromatic number not greater than K. In this paper, we focus on the inverse chromatic number problem for certain classes of graphs. First, we discuss diverse possible versions and then focus on two application frameworks which motivate this problem in interval and permutation graphs: the inverse booking problem and the inverse track assignment problem. The inverse booking problem is closely related to some previously known scheduling problems;we propose new hardness results and polynomial cases. The inverse track assignment problem motivates our study of the inverse chromatic number problem in permutation graphs;we show how to solve in polynomial time a generalization of the problem with a bounded number of colors. (C) 2014 Elsevier By. All rights reserved.
A linear time method to decide if any inverse maximum flow (denoted General inverse Maximum Flow problems (IMFG)) problem has solution is deduced. If IMFG does not have solution, methods to transform IMFG into a feasi...
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A linear time method to decide if any inverse maximum flow (denoted General inverse Maximum Flow problems (IMFG)) problem has solution is deduced. If IMFG does not have solution, methods to transform IMFG into a feasible problem are presented. The methods consist of modifying as little as possible the restrictions to the variation of the bounds of the flow. New inverse combinatorial optimization problems are introduced and solved.
Recent literature on supply chain coordination offers a wide range of game theoretic and optimization approaches that ensure efficient planning in the supply chain, but assume that the involved parties have complete i...
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Recent literature on supply chain coordination offers a wide range of game theoretic and optimization approaches that ensure efficient planning in the supply chain, but assume that the involved parties have complete information about each other. However, in reality, complete information is rarely available, and those models alone do not present any incentive for the parties to reveal their private information, e.g., the cost parameters that they use when solving their planning problems. This paper proposes an inverse lot-sizing model for eliciting the cost parameters of a supplier from historic demand vs. optimal delivery lot-size pairs, gathered during repeated earlier encounters. It is assumed that the supplier solves a single-item, multi-period, uncapacitated lot-sizing problem with backlogs to optimality to calculate its lot-sizes, and the buyer is aware of this fact. The inverse lot-sizing problem is reformulated to an inverse shortest path problem, which is, in turn, solved as a linear program. This model is used to compute the ratios of the supplier's cost parameters, i.e., the setup, the holding, and the backlog cost parameters consistent with all the historic samples. The elicited cost parameters can be used as input for various game theoretic or bilevel optimization models for supply chain coordination. Computational experiments on randomly generated problem instances indicate that the approach is very efficient in predicting future supplier actions from the historic records. (C) 2013 Elsevier B.V. All rights reserved.
Given a graph G and an independent set S of G, the 0-1 inverse maximum independent set problem (IMIS0,1) is to delete as few vertices as possible such that S becomes a maximum independent set of G. It is known that IM...
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Given a graph G and an independent set S of G, the 0-1 inverse maximum independent set problem (IMIS0,1) is to delete as few vertices as possible such that S becomes a maximum independent set of G. It is known that IMIS0,1 is NP-hard even when the given independent set has a bounded size. In this paper, we present linear-time algorithms for IMIS0,1 on forests and unicyclic graphs.
Recent literature on supply chain coordination offers a wide range of game theoretic and optimization approaches that ensure efficient planning in the supply chain, but assume that the involved parties have complete i...
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Recent literature on supply chain coordination offers a wide range of game theoretic and optimization approaches that ensure efficient planning in the supply chain, but assume that the involved parties have complete information about each other. However, in reality, complete information is rarely available, and those models alone do not present any incentive for the parties to reveal their private information, e.g., the cost parameters that they use when solving their planning problems. This paper proposes an inverse lot-sizing model for eliciting the cost parameters of a supplier from historic demand vs. optimal delivery lot-size pairs, gathered during repeated earlier encounters. It is assumed that the supplier solves a single-item, multi-period, uncapacitated lot-sizing problem with backlogs to optimality to calculate its lot-sizes, and the buyer is aware of this fact. The inverse lot-sizing problem is reformulated to an inverse shortest path problem, which is, in turn, solved as a linear program. This model is used to compute the ratios of the supplier's cost parameters, i.e., the setup, the holding, and the backlog cost parameters consistent with all the historic samples. The elicited cost parameters can be used as input for various game theoretic or bilevel optimization models for supply chain coordination. Computational experiments on randomly generated problem instances indicate that the approach is very efficient in predicting future supplier actions from the historic records. (C) 2013 Elsevier B.V. All rights reserved.
Usual inverse combinatorial optimization problems consist in modifying as little as possible the instance parameters to make a given solution optimal. In this paper we consider several extensions taking into account c...
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