Parallel Calculation of Properties of Magnetic Impurities in Metais

Novas Políticas de Invocação Paralela para Seleção Dinâmica de Servidores Replicados

Eloiza SonodaGonzalo Travieso

Wesley E. Q. de SousaNabor C. Mendonça

The computation of physical properties of dilute magnetic alloys is a computationally intensive task. In principle, it consists on the diagonalization of a huge matrix. Through the use of a suitable base and of the renormalization group method, the diagonalization can be simplified to the iterative dingonalization of a set of smaller matrices (of the order of some hundreds of lines and columns). The resulting problem is nevertheless still too large if enough precision is desired. We describe here the parallel implementation of an algorithm for this problem in a cluster. The results show that the implementation achieves good reduction of execution times, but lacks speedup and scalability due to load balancing problems. We analyze these problems and suggest paths to their resolution. Geographically replicated servers are commonly used in the internetto offer greater performance, reliability and scalability to client applications.In this context, there is the problem of how to select the replicated server thatwill best serve the request of a giving client application. This paper proposesthree novel replicated server selection policies, namely First Connection, FirstRead and Best Partial. The three policies are based on the parallel invocationprinciple, in which all replicated servers are invoked in parallel, with the differencethat all connections established with each server are now dynamicallymonitored, with slower connections being gradually killed until there is onlyone connection alive. Empirical results, obtained from the invocation of realservers replicated over several countries, show that the proposed policies performmuch better than the classical parallel invocation policy, and relativelyclose to the selection of the best server previously identified for each scenarioevaluated.

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