ABSTRACT
Chapter 24 teaches how to improve performance. Once you’ve used profiling to identify a bottleneck, you need to make it faster. It’s difficult to provide general advice on improving performance, but in this chapter we’ll see four techniques that can be applied in many situations and also a general strategy for performance optimisation that helps ensure that your faster code is still correct. Also it is easy to get caught up in trying to remove all bottlenecks. Don’t! Be pragmatic: don’t spend hours of your time to save seconds of computer time.
“Code organisation” teaches you how to organise your code to make optimisation as easy, and bug free, as possible. “Checking for existing solutions” reminds you to look for existing solutions. “Doing as little as possible” emphasises the importance of being lazy: often the easiest way to make a function faster is to let it to do less work. “Vectorise” concisely defines vectorisation, and shows you how to make the most of built-in functions. “Avoiding copies” discusses the performance perils of copying data. “Case study: t-test” pulls all the pieces together into a case study showing how to speed up repeated t-tests by about a thousand times. “Other techniques” finishes the chapter with pointers to more resources that will help you write fast code.
