I was just recently going through some old episodes from Software Engineering Radio when I came across this one episode featuring Casey Muratori, where he goes through some of his thoughts around his video from February 2023, titled "‘Clean’ Code, Horrible Performance". I was actually already aware of the video by this time, but listening through the episode gave me an itch to see these concepts in my reality, experiment them by myself.
Casey’s video is interesting, but his example is framed as moving from 35 cycles/object to 24 cycles/object being a 1.5x speedup.
Another way to look at this is, it’s a 12-cycle speedup per object.
If you’re writing a shader or a physics sim this is a massive difference.
If you’re building typical business software, it isn’t; that 10,000-line monster method does crop up, and it’s a maintenance disaster.
I think extracting “clean code principles lead to a 50% cost increase” is a message that needs taking with a degree of context.
Yup. If that 12-cycle speedup is in a hot loop, then yeah, throw a bunch of comments and tests around it and perhaps keep the “clean” version around for illustrative purposes, and then do the fast thing. Perhaps throw in a feature flag to switch between the “clean” and “fast but a little sketchy” versions, and maybe someone will make a method to memoize pure functions generically so the “clean” version can be used with minimal performance overhead.
Clean code should be the default, optimizations should come later as necessary.
Keeping the clean version around seems dangerous advice.
You know it won’t get maintained if there are changes / fixes. So by the time someone may needs to rewrite the part, or application many years later (think migration to different language) it will be more confusing than helping.
Easy solution: write tests to ensure equivalent behavior.
For what its worth , the cache locality of Vec<Box<Dyn trait>> is terrible in general, i feel like if youre iterating over a large array of things and applying a polymorphic function you’re making a mistake.
Cache locality isnt a problem when youre only accessing something once though.
So imo polymorphism has its place for non iterative-compute type work, ie web server handler functions and event driven systems.