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Abstract : |
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 running time to perform an out-of-core computation. This paper analyzes timing results on multiple-disk platforms 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, 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 file systems and target machines. 1, |
