Search results for "Vertex cover"
showing 4 items of 4 documents
Constrained Role Mining
2013
Role Based Access Control (RBAC) is a very popular access control model, for long time investigated and widely deployed in the security architecture of different enterprises. To implement RBAC, roles have to be firstly identified within the considered organization. Usually the process of (automatically) defining the roles in a bottom up way, starting from the permissions assigned to each user, is called {\it role mining}. In literature, the role mining problem has been formally analyzed and several techniques have been proposed in order to obtain a set of valid roles. Recently, the problem of defining different kind of constraints on the number and the size of the roles included in the resu…
Variable Neighborhood Search for the Vertex Separation Problem
2012
The vertex separation problem belongs to a family of optimization problems in which the objective is to nd the best separator of vertices or edges in a generic graph. This optimization problem is strongly related to other well-known graph problems; such as the Path-Width, the Node Search Number or the Interval Thickness, among others. All of these optimization problems are NP-hard and have practical applications in VLSI, computer language compiler design or graph drawing. Up to know, they have been generally tackled with exact approaches, presenting polynomial-time algorithms to obtain the optimal solution for speci c types of graphs. However, in spite of their practical applications, these…
Parametrizētu algoritmu paātrinājumi kvantu datoram
2021
Darbā tiek aplūkots, kā uz kvantu datora iespējams paātrināt zināmus parametrizētus algoritmus problēmām “Closest string”, “Cluster vertex deletion”, “Cluster editing”, “Vertex cover” un “Longest path” problēmu risinājumiem, ka arī to uzlabošana kvantu datoram, izmantojot kvantu algoritmus meklēšanas koka apstaigāšanai un dinamiskai programmēšanai. Ir parādīts, kā izveidot kvantu algoritmus “Cluster vertex deletion” problēmas risinājumam ar laika sarežģītību 𝑂(1.7321^𝑘 * √𝑘 * 𝑛^3) un “Vertex cover” problēmai ar laiku 𝑂(1.175^𝑘 * 𝑘^𝑂(1) + 𝑛√𝑚), kas ir labāk, nekā labākajiem zināmajiem algoritmiem ar laiku 𝑂(1.9102^𝑘 * (𝑛 + 𝑚)) un 𝑂(1.2738^𝑘 + 𝑘𝑛), attiecīgi. Ka arī ir parād…
On the hardness of optimization in power-law graphs
2008
Our motivation for this work is the remarkable discovery that many large-scale real-world graphs ranging from Internet and World Wide Web to social and biological networks appear to exhibit a power-law distribution: the number of nodes y"i of a given degree i is proportional to i^-^@b where @b>0 is a constant that depends on the application domain. There is practical evidence that combinatorial optimization in power-law graphs is easier than in general graphs, prompting the basic theoretical question: Is combinatorial optimization in power-law graphs easy? Does the answer depend on the power-law exponent @b? Our main result is the proof that many classical NP-hard graph-theoretic optimizati…