Editorial: Special Issue: Performance evaluation of ubiquitous computing and networked systems

In April 2008, we organised the 7th International workshop on Performance Modelling, Evaluation and Optimization of Ubiquitous Computing and Networked Systems (PMEOUCNS’2008) held in conjunction with the IEEE-IPDPS, 14–18 April 2008, Miami, Florida, USA. We selected seven high quality papers (out of 17 papers, which were presented at the workshop) and invited the authors of the selected papers to extend them and submit them for a complete new peer-review for consideration in this special issue. The final decision for the inclusion in the special issues has been strictly based on the outcome of the review process. International Journal of Parallel, Emergent and Distributed Systems (IJPEDS) is one of the well-established and reputable journals with a wide international readership. The main objective of the Special Issue is to make available the latest results in the field to the research community. The performance modelling, evaluation and optimisation of ubiquitous computing and networked systems have been an important research topic over the past years and poses challenging problems that require new tools and methods to keep up with the rapid evolution and increasing complexity of such systems. The purpose of this Special Issue is to report state-of-the-art and in-progress research on all aspects of performance modelling, evaluation, and optimisation of these systems. The selected papers span a broad range on the performance modelling and evaluation of such systems. The contributions of these papers are outlined below. The performance of collective communication operations is known to have a significant impact on the scalability of some applications. Indeed, the global, synchronous nature of some collective operations directly implies that they will become the bottleneck when scaling to hundreds of thousands of nodes. This has led many researchers to try to improve the efficiency of collective operations. Although different measurement schemes for blocking collective operations are implemented in well-known benchmarks, many of these schemes introduce different systematic errors in their measurements. Hoefler, Schneider and Lumsdaine characterise these errors and select a window-based approach as the most accurate method. However, this approach complicates measurements significantly and introduces a clock synchronisation as a new source of systematic errors. They analyse approaches to avoid or correct those errors and develop a scalable synchronisation scheme to conduct benchmarks on massively parallel systems. Their results are compared to the window-based scheme implemented in the SKaMPI