--ZusammenfassungCirculant Block-Factorization Preconditioners for Elliptic Problems. New circulant block-factorization preconditioners are introduced and studied. The general approach is first formulated for the case of block tridiagonal sparse matrices. Then estimates of the relative condition number for a model Dirichlet boundary value problem are derived. In the case of y-periodic problems the circulant block-factorization preconditioner is shown to give an optimal convergence rate. Finally, using a proper imbedding of the original Dirichlet boundary value problem to a y-periodic one a preconditioner of optimal convergence rate for the general case is obtained. The total computational cost of the preconditioner is O(N log N) (based on FFT), where N is the number of unknowns. That is, the algorithm is nearly optimal Various numerical tests that demonstrate the features of the circulant block-factorization preconditioners are presented. AMS Subject Classification: 65F10, 65N20Key words: Preconditioning, circulant matrices, FFT, elliptic problems, block-tridiagonal matrices, conjugate gradients.Zyklische Matrixzerlegung zur Priikonditioniertmg elliptischer Aufgaben. Neue zyklische Matrixzerlegungen werden eingefiihrt und untersucht. Der allgemeine Ansatz wird fiir den Fall blocktridiagonaler schwachbesetzter Matrizen formuliert. Danach werden Absch~itzungen der relativen Konditionszahl fiir ein Dirichlet-Modellproblem abgelcitet. Es wird gezeigt, dab die zyklische Matrixzerlegung im Falle y-periodischer Aufgaben optimale Konvergenzraten liefert. Nach Einbettung des urspriinglichen Dirichlet-Problems in eine y-periodische Aufgabe erhiilt man den allgemeinen Fall. Der Gesamtaufwand des Pr~ikonditionierers betr~igt O(N log N) gem~iB des FFT-Aufwandes, wobei N die Zahl der Unbekannten ist. Damit ist der Algorithmus fast optimal. Verschiedene numerische Tests zeigen die Eigenschaften der zyklischen Matrixzerlegung.

International audienceOur research (the Agents in Grid; AiG project) concerns the development of an agent-based Grid middleware, in which (a) agents work in teams (each team is to be managed by the LMaster agent), (b) all meta-information is ontologically demarcated and semantically processed (with all team information stored in and managed by the Client Information Center; CIC infrastructure represented by the CIC agent), and (c) an economic model is to be based on autonomic Service Level Agreement (SLA) negotiations and Quality of Service (QoS) monitoring

Abstract. Recently we have proposed an approach to utilizing agent teams as resource brokers and managers in the Grid. Thus far we have discussed the general overview of the proposed system, how to efficiently implement matchmaking services, as well as proposed a way by which agents select a team that will execute their job. In this paper we focus our attention on processes involved in agents joining a team.

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