Date of Award


Document Type

Thesis (Undergraduate)

Department or Program

Department of Computer Science

First Advisor

Tom Cormen


This paper discusses our implementation of Rajasekaran's (l,m)-mergesort algorithm (LMM) for sorting on parallel disks. LMM is asymptotically optimal for large problems and has the additional advantage of a low constant in its I/O complexity. Our implementation is written in C using the ViC* I/O API for parallel disk systems. We compare the performance of LMM to that of the C library function qsort on a DEC Alpha server. qsort makes a good benchmark because it is fast and performs comparatively well under demand paging. Since qsort fails when the swap disk fills up, we can only compare these algorithms on a limited range of inputs. Still, on most out-of-core problems, our implementation of LMM runs between 1.5 and 1.9 times faster than qsort, with the gap widening with increasing problem size.


Originally posted in the Dartmouth College Computer Science Technical Report Series, number PCS-TR99-351.