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by jcranmer 874 days ago
There's been more than a few of these "nature solves NP-hard problems quickly!" kinds of stories, but usually, when one digs deeper, the answer is "nature finds local optima for NP-hard problems quickly!" and the standard response is "so does pretty trivial computer algorithms."

In the case of TSP, when you're trying to minimize a TSP with a Euclidean metric (i.e., each node has fixed coordinates, and the cost of the path is the Euclidean distance between these two points), then we can actually give you a polynomial-time algorithm to find a path within a factor ε of the optimal solution (albeit exponential in ε).

1 comments

https://scottaaronson.blog/?p=266

""" I went to the hardware store, bought some glass plates, liquid soap, etc., and found that, while Nature does often find a minimum Steiner tree with 4 or 5 pegs, it tends to get stuck at local optima with larger numbers of pegs. """

:-) Well, nature also makes you, and you solve problems? So by transitivity ...
"Did he try jiggling it a bit, and then less and less and less?"

( Annealing /s )