Measuring the scalability of parallel computer systems

This paper discusses scalability and outlines a specific approach to measuring the scalability of parallel computer systems. The relationship between scalability and speedup is described. It is shown that a parallel system is scalable for a given algorithm if and only if its speedup is unbounded. A technique is proposed that can be used to help determine whether a candidate model is correct, that is, whether it adequately approximates the system's scalability. Experimental results illustrate this technique for both a poorly scalable and a very scalable system.