Toward an understanding of the building blocks: constructing programs for high processor count systems

Technology and industry trends have clearly shown that the future of technical computing lies in exploitation of more processors in larger multiprocessor systems. Exploitation of high processor count architectures demands a more thorough understanding of the underlying system dynamics and an accounting for them in the design of high-performance applications. Currently these dynamics are incompletely described by the widely adopted benchmarks and kernel metrics. Systems are most often characterized to allow comparisons and ranking. Often the characterizations are in the form of a scalar measure of some aspect of system performance that is a 'not to exceed' number: the maximum possible level of performance that could be attained. While such comparisons typically drive both system design and procurement, more useful characterizations can be used to drive application development and design. This paper explores a few of these measures and presents a few simple examples of their application. The first set of metrics addresses individual processor performance, specifically performance related to memory references. The second set of metrics attempts to describe the behavior of the message-passing system under load and across a range of conditions.