Introduction

If concurrent processing has performance implications when structuring programs, parallel processing is a way to get better performance that has implications on how we structure our programs. Although they are often conflated, concurrent processing and parallel processing are different solutions to different problems. Concurrency is good for expressing programs that involve different tasks that can be, or must be, carried out at the same time. Parallelization is a good option if you want to perform the same task many times, all at once. Parallelization is not necessary, but it can help tremendously with your program's performance.

Earlier, the easiest, and often best, strategy to improve performance was to go on a vacation. Moore's law implies that processor speed will double approximately every 18 months, so in the 1990s, we could go on vacation, return, buy a new computer, and our programs were faster. This was magic.

Today, we're no longer under Moore's law, instead, as the...