Parallel programming is elusive. The relative performance of di erent parallel implementations varies with machine architecture, system and problem size. How to compare di erent implementations over a wide range of machine architectures and problem sizes has never been well addressed due to its di culty. Scalability has been proposed in recent years to reveal scaling properties of parallel algorithms and machines. In this paper, based on scalability analysis, the concepts of crossing point analysis and range comparison are introduced. Crossing point analysis nds slow fast performance crossing points of parallel algorithms and machines. Range comparison compares performance over a wide range of ensemble and problem size via scalability and crossing point analysis. Three algorithms from scienti c computing are implemented on an Intel Paragon and an IBM SP2 parallel computer. Experimental and theoretical results show the combination of scalability, crossing point analysis, and range comp...