Where benefits will accrue

A program that does a great deal of calculation and relatively little I/O will not see much benefit from concurrent processing. If a calculation has a budget of 28 minutes of computation, then interleaving the operations in different ways won't have very much impact. Switching from strict to non-strict evaluation of 100 billion bytecodes won't shrink the elapsed execution time.

However, if a calculation involves a great deal of I/O, then interleaving CPU processing and I/O requests can have an impact on performance. Ideally, we'd like to do our computations on some pieces of data while waiting for the OS to complete input of the next pieces of data.

We have two approaches to interleaving computation and I/O. They are as follows:

• We can try to interleave I/O and calculation for the entire problem as a whole. We might create a pipeline of processing with read, compute, and write as operations. The idea is to have individual data objects flowing through the pipe from...