Document Type

Technical Report

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Technical Report Number



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.


Revised version appeared in Parallel Computing 23(4), June 1997. Original version August 7, 1996; revised version September 6, 1996.