Chapter 12. Performance
This chapter covers
Now that we’ve spent a book’s worth of material learning the why and how of Clojure, it’s high time we turned our attention to the subject of performance. There’s a meme in programming that can be summarized as follows: make it work first, then make it fast. Throughout this book, we’ve taught you the ways that Clojure allows you to “make it work,” and now we’re going to tell how to make it fast.
In many cases, Clojure’s compiler will be able to highly optimize idiomatic Clojure source code. But there are times when the form of your functions, especially in interoperability scenarios, will prove to be ambiguous or even outright counter to compiler optimizations. Therefore, we’ll lead you through optimization techniques such as type hints, transients, chunked sequences, memoization, and coercion. Using some combination of these techniques will help you approach, and sometimes exceed, the performance of Java itself.
The most obvious place to start, and the one you’re most likely encounter, is type hinting—so this is where we’ll begin.