Despite the increasing demand for utilizing HPC for CSE applications, software development for HPC historically attracted little attention from the SE community. Paradoxically, the HPC CSE community has increasingly been adopting SE techniques and tools. Indeed, the development of CSE software for HPC differs significantly from the development of more traditional business inforåmation systems, from which many SE best practices and tools have been drawn. This workshop, the fourth in the series to be co-located with the Supercomputing conference series, examined two main topics: testing and trade-offs. Through presentations of work in this area and structured group discussions, the participants highlighted some of the key issues, as well as indicating the direction the community needed to go. In particular, there is a need for more high-quality research in this area that we can use as an evidence base to help developers of CSE applications to change practice and benefit from advances in software engineering.