Along with the rapid development of parallel processing technology and the popularity of NOW,the scalability of parallel algorithm-machine combinations,which measures the capacity of a parallel algorithm to effectively utilize an increasing number of processors ,becomes more and more important. In this paper ,we present a new metric ,called time_scale metric ,to measure and evaluate the scalability of parallel algorithms and machines,and extend it to fit the characteristics of NOW. The experimental results show that the time-scale metric is a practical and accurate method to evaluate the scalability of parallel algorithms on MPP and NOW.
