Abstract

Abstract

Abstract

Abstract

Abstract
This paper considers the single machine scheduling problem with weighted quadratic tardiness costs. Three metaheuristics are presented, namely iterated local search, variable greedy and steady-state genetic algorithm procedures. These address a gap in the existing literature, which includes branch-and-bound algorithms (which can provide optimal solutions for small problems only) and dispatching rules (which are efficient and capable of providing adequate solutions for even quite large instances). A simple local search procedure which incorporates problem specific information is also proposed. The computational results show that the proposed metaheuristics clearly outperform the best of the existing procedures. Also, they provide an optimal solution for all (or nearly all, in the case of the variable greedy heuristic) the smaller size problems. The metaheuristics are quite close in what regards solution quality. Nevertheless, the iterated local search method provides the best solution, though at the expense of additional computational time. The exact opposite is true for the variable greedy procedure, while the genetic algorithm is a good all-around performer.

Abstract
This paper presents CloudAnchor, a brokerage platform conceived to help Small and Medium Sized Enterprises (SME) embrace Infrastructure as a Service (IaaS) cloud computing both as providers and consumers. The platform, which transacts automatically single and federated IaaS cloud resources, is a multi-layered Multi-Agent System (MAS) where providers, consumers and virtual providers, representing provider coalitions, are modelled by dedicated agents. Federated resources are detained and negotiated by virtual providers on behalf of the corresponding coalition of providers. CloudAnchor negotiates and establishes Service Level Agreements (SLA) on behalf of SME businesses regarding the provision of brokerage services as well as the provision of single and federated IaaS resources. The discovery, invitation, acceptance and negotiation processes rely on a distributed trust model designed to select the best business partners for consumers and providers and improve runtime.