For many scientific researchers, a lot of the point of ESC is to utilize the highest scale of supercomputing to reduce the “time to science”. In order to quantify progress toward this goal, a way to measure the time it takes for a program to run as a function of the resources used plays an ostensibly critical role. So also is staying abreast of the most recent features of ESC hardware and software. This chapter begins by discussing the basics of timing MPI programs, as well as the concepts of scalability and efficiency. The chapter finishes with some highlighting of more recently introduced features into the MPI standard: advanced collectives and one-sided communication.