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. Typiccdly, the cost models proposed
for external memory algorithms have measured only the number of 1/0 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 …

External memory (EM) algorithms are designed for large-scale computational problems in
which the size of the internal memory of the computer is only a small fraction of the problem
size. Typical EM algorithms are specially crafted for the EM situation. In the past, several
attempts have been made to relate the large body of work on parallel algorithms to EM, but
with limited success. The combination of EM computing, on multiple disks, with
multiprocessor parallelism has been posted as a challenge by the ACM Working Group on …