Abstract

Although several algorithms have been developed for the Parallel Disk Model (PDM), few have beenimplemented. Consequently, little has been known about the accuracy of thePDMin measuring I/O time and total running time to perform an out-of-core computation. This paper analyzes timing results on multiple-disk platforms fortwo PDM algorithms, out-of-core radix sort and BMMC permutations, to determine the strengths and weaknesses of thePDM. The results indicate the following. First, good PDM algorithms are usually not I/O bound. Second, of the four PDM parameters, one (problem size) is a good indicator of I/O time and running time, one (memory size) is a good indicator of I/O time but not necessarily running time, and the other two (block size and number of disks) do not necessarily indicate either I/O or running time. Third, because PDM algorithms tend not to be I/O bound, using asynchronous I/O can reduce I/O wait times significantly. 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 underlying le systems and target machines.

Citations