F. Dehne, W. Dittrich, and D. Hutchinson, Efficient
External Memory Algorithms by Simulating Coarse-Grained Parallel Algorithms,
Proc. Symposium on Parallel Algorithms and Architectures (SPAA'97), Newport
R.I., USA, June 1997.
External memory (EM) algorithms are designed for computational problems
in which the size of the internal memory of the computer is only a small
fraction of the problem size. For certain large scale applications this
is necessarily true. Typically, the cost models proposed for external memory
algorithms have measured only the number of I/O operations, and the algorithms
have been specially crafted for the EM situation. In the past, several
attempts have been made to relate the large body of work based on parallel
algorithms to EM, but with limited success. In this paper we provide simulation
techniques which produce efficient EM algorithms from efficient algorithms
developed under BSP-like parallel computing models. Our techniques can
accommodate one or multiple processors on the EM target machine, each with
one or more disks, and they also adapt to the disk blocking factor of the
target machine. In addition to the main simulation result we obtain a more
comprehensive cost model for EM algorithms, which considers the total costs
incurred by the algorithm including computation, I/O and communication
costs.