Performance Evaluation of Local Communications: A Case-study

S.R. Alam, R.N. Ibbett, and F. Mallet (UK)


Supercomputing, Interconnection Networks, Network Per formance, Modelling and Simulation


Wire densities of interconnection networks is a criti cal design consideration for Massively-Parallel Processing (MPP) supercomputers with tens of thousands of process ing nodes. In these MPPs, high-bandwidth parallel buses are increasingly replaced by high performance and reli able serial links, which allow increased network connectiv ity i.e., multiple communication ports per processing node. Nevertheless these bit-serial links are affected by channel errors. The re-transmission costs on these comparatively low-bandwidth networks can have a significant impact on the performance of an application code, particularly for al gorithms requiring frequent local communications. This research analyses the impact of communication buffer sizes and associated transmission protocols on off-node commu nication performance of an MPP system called QCDOC.

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