Hacker News Reader

Comment by frankreyes | Hacker News Reader

Haskell type inference is EXPTIME, O(2^p(n)), yet it works fine in practice. This reminds me of the quote by Rob Pike on algorithms completely:

>>Rule 3. Fancy algorithms are slow when n is small, and n is usually small. Fancy algorithms have big constants. Until you know that n is frequently going to be big, don’t get fancy.

https://en.m.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_...

View on HN

That rule, while sensible at the time, has aged pretty poorly. n used to be small in the 70s, but now people have terabytes of data and run UNIX tools over them.

Sorta. What we consider a small N has also gotten surprisingly large.

Latest epyc CPU have 768MB of L3 cache. You can run Linux entirely on L3 memory.

https://www.amd.com/en/press-releases/2022-03-21-3rd-gen-amd...

> You can run Linux entirely on L3 memory.

Is that a theoretical possibility based on the fact that Linux can run in a memory footprint < 768MB, or has someone actually demonstrated it? Can you boot one of these processors without any RAM installed?

It's my wild unfounded guess, I guess ^_^

Any modern CPU needs RAM, specially to get things to cache, I don't think there's any way around it.

What I was trying to say is that having a large L3 means that it never has to wait for RAM access, and that should be fast.

Coreboot sets up cache as RAM through memory mapping tricks, to have something a normal C compiler can work with. (DRAM needs to be trained and set up properly before you have any RAM; before that, you have only registers, which is pretty painful.)

CPU cache have gotten larger. For example, Latest epyc CPU have 768MB of L3 cache. You can run Linux entirely on L3 memory...

https://www.amd.com/en/press-releases/2022-03-21-3rd-gen-amd...

This reasoning works okay until you have to deal with machine-generated inputs, at which point your app freezes when it gets sent down a quadratic or worse complexity path.

Oh yeah I've seen autogenerated source code ... It freezes my browser trying to syntax highlighting it. Raw works fine.

Reply on news.ycombinator.com