Early Experiences in Evaluating the Parallel Disk Model with the ViC* Implementation

Although several algorithms have been developed for the Parallel Disk Model (PDM), few have been implemented. Consequently, little has been known about the accuracy of the PDM in measuring I/O time and total time to perform an out-of-core computation. This paper analyzes timing results on a uniprocessor with several disks for two PDM algorithms, out-of-core radix sort and BMMC permutations, to determine the strengths and weaknesses of the PDM. The results indicate the following. First, good PDM algorithms are usually not I/O bound. Second, of the four PDM parameters, two (problem size and memory size) are good indicators of I/O time and running time, but the other two (block size and number of disks) are not. Third, because PDM algorithms tend not to be I/O bound, asynchronous I/O effectively hides I/O times. The software interface to the PDM is part of the ViC* run-time library. The interface is a set of wrappers that are designed to be both efficient and portable across several parallel file systems and target machines.