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goosethe@lemmy.sdf.org

What's a concrete example of LIN ⊊ NLIN? (lemmy.sdf.org)

submitted 1 week ago by CanadaPlus@lemmy.sdf.org to c/math@lemmy.sdf.org

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I've read the old papers proving that fact, but honestly it seems like some of the terminology and notation has changed since the 70's, and I roundly can't make heads or tails of it. The other sources I can find are in textbooks that I don't own.

Ideally, what I'm hoping for is a segment of pseudocode or some modern language that generates an n-character string from some kind of seed, which then cannot be recognised in linear time.

It's of interest to me just because, coming from other areas of math where inverting a bijective function is routine, it's highly unintuitive that you provably can't sometimes in complexity theory.

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[–] CanadaPlus@lemmy.sdf.org 2 points 1 week ago* (last edited 1 week ago) (1 children)

Ah sorry, I had no idea, you could have been a topologist who doesn't like computers or something.

LIN is unusual to hear about, probably because it's pretty well understood. Are you more of a coder, or an actual, academic computer scientist? If the latter, what do you know about pebbling games on nondeterministic machines?

[–] jacksilver@lemmy.world 1 points 1 week ago (1 children)

Oh no worries, I think I stumbled on this in a computer science crosspost.

While I do lean a bit in the academics, my area is mostly in ML / AI so not well read in pebbling games (although it sounds interesting).

[–] CanadaPlus@lemmy.sdf.org 1 points 1 week ago* (last edited 1 week ago)

Yeah, the first paper I read was pretty heavily reliant on them. As far as I can tell they're laying the pebbles on the execution tree of a nondeterministic machine and then proving something with that.