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Caching is an abstraction, not an optimization

(buttondown.com)
134 points samuel246 | 3 comments | 01 Jul 25 10:42 UTC | HN request time: 0.571s | source
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ckdot2 ◴[03 Jul 25 19:03 UTC] No.44458190[source]▶
"I think now caching is probably best understood as a tool for making software simpler" - that's cute. Caching might be beneficial for many cases, but if it doesn't do one thing then this is simplifying software. There's that famous quote "There are only two hard things in Computer Science: cache invalidation and naming things.", and, sure, it's a bit ironical, but there's some truth in there.
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EGreg ◴[03 Jul 25 19:41 UTC] No.44458502[source]▶
I never understood about cache invalidation or naming things

Both are not that difficult, honestly.

Aren’t there a lot harder things out there

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IshKebab ◴[03 Jul 25 20:31 UTC] No.44458913[source]▶
Cache invalidation isn't hard in theory. It's just one of those things that is very easy to get subtly wrong and difficult to test.

Think about all those times your program isn't building and `make clean` fixes it.

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1. throwaway150 ◴[03 Jul 25 22:24 UTC] No.44459653[source]▶
> Think about all those times your program isn't building and `make clean` fixes it.

I don't think that's a good example. I've worked with more than 20 different build tools by now, and I cannot recall a single instance where the problem actually came down to cache invalidation. Every time I dug into it, the real cause was something else: a mistake in the build script, an incorrectly declared dependency, or something similar.

So when you say "think about all those times", not a single such time comes to my mind!

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2. degamad ◴[04 Jul 25 01:50 UTC] No.44460506[source]▶
I think the idea is that if make clean allows the build to complete correctly, then the underlying issue is that the "mistake in the build script, incorrectly declared dependency, or similar" was causing the cached build results to not be invalidated when they should have.
3. IshKebab ◴[04 Jul 25 10:59 UTC] No.44463400[source]▶
> an incorrectly declared dependency

That literally IS cache invalidation. Incremental build systems are caching previous artefacts. They're supposed to invalidate the artefact if a dependency changes. But you forgot to declare the dependency... so it doesn't get invalidated when it should.