scholarly journals Randomized rounding algorithms for large scale unsplittable flow problems

Author(s):  
François Lamothe ◽  
Emmanuel Rachelson ◽  
Alain Haït ◽  
Cedric Baudoin ◽  
Jean-Baptiste Dupé
Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1716
Author(s):  
Adrian Marius Deaconu ◽  
Delia Spridon

Algorithms for network flow problems, such as maximum flow, minimum cost flow, and multi-commodity flow problems, are continuously developed and improved, and so, random network generators become indispensable to simulate the functionality and to test the correctness and the execution speed of these algorithms. For this purpose, in this paper, the well-known Erdős–Rényi model is adapted to generate random flow (transportation) networks. The developed algorithm is fast and based on the natural property of the flow that can be decomposed into directed elementary s-t paths and cycles. So, the proposed algorithm can be used to quickly build a vast number of networks as well as large-scale networks especially designed for s-t flows.


IEEE Access ◽  
2021 ◽  
Vol 9 ◽  
pp. 56604-56615
Author(s):  
Manolo D'orto ◽  
Svante Sjoblom ◽  
Lung Sheng Chien ◽  
Lilit Axner ◽  
Jing Gong

2012 ◽  
Vol 12 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Petia Boyanova ◽  
Minh Do-Quang ◽  
Maya Neytcheva

AbstractIn this work we consider preconditioned iterative solution methods for numerical simulations of multiphase flow problems, modelled by the Cahn-Hilliard equation. We focus on diphasic flows and the construction and efficiency of a preconditioner for the algebraic systems arising from finite element discretizations in space and the θ-method in time. The preconditioner utilises to a full extent the algebraic structure of the underlying matrices and exhibits optimal convergence and computational complexity properties. Various numerical experiments, including large scale examples, are presented as well as performance comparisons with other solution methods.


2019 ◽  
Vol 21 (2) ◽  
pp. 485-515 ◽  
Author(s):  
Ricardo B. N. M. Pinheiro ◽  
Leonardo Nepomuceno ◽  
Antonio R. Balbo

Author(s):  
Paul Dütting ◽  
Thomas Kesselheim ◽  
Éva Tardos

Many algorithms that are originally designed without explicitly considering incentive properties are later combined with simple pricing rules and used as mechanisms. A key question is therefore to understand which algorithms, or, more generally, which algorithm design principles, when combined with simple payment rules such as pay your bid, yield mechanisms with a small price of anarchy. Our main result concerns mechanisms that are based on the relax-and-round paradigm. It shows that oblivious rounding schemes approximately preserve price of anarchy guarantees provable via smoothness. By virtue of our smoothness proofs, our price of anarchy bounds extend to Bayes–Nash equilibria and learning outcomes. In fact, they even apply out of equilibrium, requiring only that agents have no regret for deviations to half their value. We demonstrate the broad applicability of our main result by instantiating it for a wide range of optimization problems ranging from sparse packing integer programs, over single-source unsplittable flow problems and combinatorial auctions with fractionally subadditive valuations, to a maximization variant of the traveling salesman problem.


2016 ◽  
Vol 2016.26 (0) ◽  
pp. 2310
Author(s):  
Kentaro YAJI ◽  
Masao OGINO ◽  
Shinji NISHIWAKI ◽  
Kikuo FUJITA

Author(s):  
Philip Diwakar ◽  
Vibhor Mehrotra ◽  
Rimon Vallavanatt ◽  
Thomas McLean

Industrial application of Computational Fluid Dynamics (CFD) are varied and many. However CFD requires the solution of complex fluid-flow problems in conjunction with equipment design, process and product development and optimization. The solution of such complex problems is possible through the coordination between industrial CFD engineers, software developers, consultants and academic scientists. In the petrochemical industry, CFD may be used for a variety of purposes such as air recirculation studies in LNG plants, burners in coker furnaces, multiphase studies in heat exchangers to name just a few. In particular combustion, flames, flares and chemical reaction are of interest because of the physics and the complex nature of the process. The topic selected for this presentation is the study of wet ground flares during a large-scale propane release and the effect of the radiation release on the environment and surrounding buildings and vegetation. The flare characteristics and radiation on the surrounding terrain form an integral part of the information required by the National standard for “Control of Major Hazard Facilities”. The study of individual flames from each burner with nozzles of the order of 1mm and the effect of 180 burners in a large area and surrounding terrain with length scales of several hundred meters make up a very intriguing problem of varying length scales. The results of this analysis are presented concentrating on the effects during the large scale conflagration event on the surrounding buildings, vegetation, aircraft, hills and mangroves.


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