With respect to a good tradition, I’m publishing a blog post based on my ScalaMatsuri talk covering a few performance lessons I learned working on Finch. Even though these lessons are coming from a foundation library, I tend to believe they can be projected into any Scala (or even Java) codebase no matter if it’s an HTTP library or a user-facing application.

This post is based on my talk “Finagle: Under the Hood” that was presented at Scala Days NYC. I thought I’d publish this for those who prefer reading instead of watching (video is not yet published anyway). The full slide deck is available online as well.

Turns out I’ve never mentioned anything about Finch, a library I’m working on most of my free time, in my personal blog. So I decided to finally fix that and write a small note on what I think about Finch’s performance as an HTTP library/server. To be more precise, I want to comment the most recent results of the TechEmpower benchmark and perhaps, give some insights on why Finch is ranked so high there.

Functional programming nicely leverages constraints on how programs are written thereby promoting a clean and easy to reason about coding style. Purely functional data structures are (surprisingly) built out of those constraints. They are persistent (FP implies that both old and new versions of an updated object are available) and backed by immutable objects (FP doesn’t support destructive updates). Needless to say, it’s a challenge to design a purely functional data structure that meets performance requirements of its imperative sibling. Fortunately, it’s quite possible in most of the cases, even for those data structures whose reference implementations are backed by mutable arrays. This post precisely describes a process of designing a purely functional implementation technique for Standard Binary Heaps, with the same asymptotic bounds as in an imperative setting.

Combinatorics is a branch of mathematics that mostly focuses on problems of counting the structures of given size and kind. The most famous and well-known examples of such problems might be often asked as job interview questions. This blog post presents four generational problems (combinations, subsets, permutations and variations) along with their purely functional implementations in Scala.