LogGP in theory and practice – An in-depth analysis of modern interconnection networks and benchmarking methods for collective operations

Accurate measurement and modeling of network performance is important for predicting and optimizing the running time of high-performance computing applications. Although the LogP family of models has proven to be a valuable tool for assessing the communication performance of parallel architectures, non-intrusive LogP parameter assessment of real systems remains a difficult task. Based on an analysis of accuracy and contention properties of existing measurement methods, we develop a new low-overhead measurement method which also assesses protocol changes in the underlying transport layers. We use the gathered parameters to simulate LogGP models of collective operations and demonstrate the errors in common benchmarking methods for collective operations. The simulations provide new insight into the nature of collective algorithms and their pipelining properties. We show that the error of conventional benchmark methods can grow linearly with the system size.