The present paper compares the application of one deterministic and three non-deterministic optimization algorithms to global transformer design optimization. One deterministic optimization algorithm (Mixed Integer No...
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ISBN:
(纸本)9781467301428
The present paper compares the application of one deterministic and three non-deterministic optimization algorithms to global transformer design optimization. One deterministic optimization algorithm (Mixed Integer Nonlinear Programming), is compared to three non-deterministic approaches (Harmony Search, Differential Evolution and Genetic Algorithm). The comparison yields significant conclusions on the efficiency of the algorithms and the selection of the most suitable for the transformer design optimization problem.
Submodular maximization is one of the central topics in combinatorial optimization. It has found numerous applications in the real world. In the past decades, a series of algorithms have been proposed for this problem...
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ISBN:
(纸本)9783031221040;9783031221057
Submodular maximization is one of the central topics in combinatorial optimization. It has found numerous applications in the real world. In the past decades, a series of algorithms have been proposed for this problem. However, most of the state-of-the-art algorithms are randomized. There remain non-negligible gaps with respect to approximation ratios between deterministic and randomized algorithms in submodular maximization. In this paper, we propose deterministic algorithms with improved approximation ratios for non-monotone submodular maximization. Specifically, for the matroid constraint, we provide a deterministic 0.283 - o(1) approximation algorithm, while the previous best deterministic algorithm only achieves a 1/4 approximation ratio. For the knapsack constraint, we provide a deterministic 1/4 approximation algorithm, while the previous best deterministic algorithm only achieves a 1/6 approximation ratio.
Randomization is a fundamental tool used in many theoretical and practical areas of computer science. We study here the role of randomization in the area of submodular function maximization. In this area most algorith...
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ISBN:
(纸本)9781510819672
Randomization is a fundamental tool used in many theoretical and practical areas of computer science. We study here the role of randomization in the area of submodular function maximization. In this area most algorithms are randomized, and in almost all cases the approximation ratios obtained by current randomized algorithms are superior to the best results obtained by known deterministic algorithms. Derandomization of algorithms for general submodular function maximization seems hard since the access to the function is done via a value oracle. This makes it hard, for example, to apply standard derandomization techniques such as conditional expectations. Therefore, an interesting fundamental problem in this area is whether randomization is inherently necessary for obtaining good approximation ratios. In this work we give evidence that randomization is not necessary for obtaining good algorithms by presenting a new technique for derandomization of algorithms for submodular function maximization. Our high level idea is to maintain explicitly a (small) distribution over the states of the algorithm, and carefully update it using marginal values obtained from an extreme point solution of a suitable linear formulation. We demonstrate our technique on two recent algorithms for unconstrained submodular maximization and for maximizing submodular function subject to a cardinality constraint. In particular, for unconstrained submodular maximization we obtain an optimal deterministic 1/2-approximation showing that randomization is unnecessary for obtaining optimal results for this setting.
The Lovasz Local Lemma (LLL) is a powerful result in probability theory that states that the probability that none of a set of bad events happens is nonzero if the probability of each event is small compared to the nu...
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ISBN:
(纸本)9780898717013
The Lovasz Local Lemma (LLL) is a powerful result in probability theory that states that the probability that none of a set of bad events happens is nonzero if the probability of each event is small compared to the number of events that depend on it. It is often used in combination with the probabilistic method for non-constructive existence proofs. A prominent application is to k-CNF formulas, where LLL implies that, if every clause in the formula shares variables with at most d≤2~k/e other clauses then such a formula has a satisfying assignment. Recently, a randomized algorithm to efficiently construct a satisfying assignment was given by Moser.
Submodular maximization is one of the central topics in combinatorial optimization. It has found numerous applications in the real world. In the past decades, a series of algorithms have been proposed for this problem...
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Submodular maximization is one of the central topics in combinatorial optimization. It has found numerous applications in the real world. In the past decades, a series of algorithms have been proposed for this problem. However, most of the state-of-the-art algorithms are randomized. There remain non-negligible gaps with respect to approximation ratios between deterministic and randomized algorithms in submodular *** this paper, we propose deterministic algorithms with improved approximation ratios for non-monotone submodular maximization. Specifically, for the matroid constraint, we provide a deterministic 0.283 - ������(1) approximation algorithm, while the previous best deterministic algorithm only achieves a 1/4 approximation ratio. For the knapsack constraint, we provide a deterministic 1/4 approximation algorithm, while the previous best deterministic algorithm only achieves a 1/6 approximation ratio. For the linear packing constraints with large widths, we provide a deterministic 1/6 - ������ approximation algorithm. To the best of our knowledge, there is currently no deterministic approximation algorithm for the constraints.
Piecewise continuous reconstruction of real-valued data can be formulated in terms of nonconvex optimization problems. Both stochastic and deterministic algorithms have been devised to solve them. The simplest such re...
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Piecewise continuous reconstruction of real-valued data can be formulated in terms of nonconvex optimization problems. Both stochastic and deterministic algorithms have been devised to solve them. The simplest such reconstruction process is the weak string. Exact solutions can be obtained for it and are used to determine the success or failure of the algorithms under precisely controlled conditions. It is concluded that the deterministic algorithm (graduated nonconvexity) outstrips stochastic (simulated annealing) algorithms both in computational efficiency and in problem-solving power.
At SODA'93, Chazelle and Matousek presented a derandomization of Clarkson's sampling-based algorithm [FOCS'88] for solving linear programs with n constraints and d variables in d(7+o(1))dn deterministic ti...
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ISBN:
(纸本)9781510819672
At SODA'93, Chazelle and Matousek presented a derandomization of Clarkson's sampling-based algorithm [FOCS'88] for solving linear programs with n constraints and d variables in d(7+o(1))dn deterministic time. The time bound can be improved to d(5+o(1))dn with subsequent work by Bronnimann, Chazelle, and Matousek [FOCS'93]. We first point out a much simpler derandomization of Clarkson's algorithm that avoids ε-approximations and runs in d~((3+o(1))d)n time. We then describe a few additional ideas that eventually improve the deterministic time bound to d~((1/2+o(1))d)n.
An interprocessor communication scheme is a key to exploit parallel computers effectively. One of the efficient communication schemes on hypercubes is the two-phased randomized routing algorithm. In this paper, the pe...
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ISBN:
(纸本)078031445X
An interprocessor communication scheme is a key to exploit parallel computers effectively. One of the efficient communication schemes on hypercubes is the two-phased randomized routing algorithm. In this paper, the performance of this randomized routing algorithm is studied. In addition, the performance of a deterministic routing algorithm, the greedy routing algorithm is evaluated.
This article addresses the challenge of selecting the most suitable optimization algorithm by presenting a comprehensive computational comparison between stochastic and deterministic methods. The complexity of algorit...
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This article addresses the challenge of selecting the most suitable optimization algorithm by presenting a comprehensive computational comparison between stochastic and deterministic methods. The complexity of algorithm selection arises from the absence of a universal algorithm and the abundance of available options. Manual selection without comprehensive studies can lead to suboptimal or incorrect results. In order to address this issue, we carefully selected 25 promising and representative state-of-the-art algorithms from both aforementioned classes. The evaluation with up to the 20 dimensions and large evaluation budgets $(10<^>{5}{\times }n)$ was carried out in a significantly expanded and improved version of the DIRECTGOLib v2.0 library, which included ten distinct collections of primarily continuous test functions. The evaluation covered various aspects, such as solution quality, time complexity, and function evaluation usage. The rankings were determined using statistical tests and performance profiles. When it comes to the problems and algorithms examined in this study, EA4eig, EBOwithCMAR, APGSK-IMODE, 1-DTC-GL, OQNLP, and DIRMIN stand out as superior to other derivative-free solvers in terms of solution quality. While deterministic algorithms can locate reasonable solutions with comparatively fewer function evaluations, most stochastic algorithms require more extensive evaluation budgets to deliver comparable results. However, the performance of stochastic algorithms tends to excel in more complex and higher-dimensional problems. These research findings offer valuable insights for practitioners and researchers, enabling them to tackle diverse optimization problems effectively.
We consider the problem of finding a maximum independent set (MaxIS) of chordal graphs using mobile agents. Suppose n agents are initially placed arbitrarily on the nodes of an n-node chordal graph G = (V, E). Agents ...
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ISBN:
(纸本)9783031814037;9783031814044
We consider the problem of finding a maximum independent set (MaxIS) of chordal graphs using mobile agents. Suppose n agents are initially placed arbitrarily on the nodes of an n-node chordal graph G = (V, E). Agents need to find a maximum independent set M of G such that each node of M is occupied by at least one agent. Also, each of the n agents must know whether its occupied node is a part of M or not. Starting from both rooted and arbitrary initial configuration, we provide distributed algorithms for n mobile agents having O(log n) memory each to compute the MaxIS of G in O(mnlog Delta) time, where m denotes the number of edges in G and Delta is the maximum degree of the graph. Agents do not need prior knowledge of any parameters if the initial configuration is rooted. For arbitrary initial configuration, agents need to know few global parameters beforehand. We further show that using a similar approach it is possible to find the maximum clique in chordal graphs and color any chordal graph with the minimum number of colors. We also provide a dynamic programming-based approach to solve the MaxIS finding problem in trees in O(n) time.
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