Peter_de_Blanc comments on Complexity of Value ≠ Complexity of Outcome - Less Wrong

32 Post author: Wei_Dai 30 January 2010 02:50AM

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Comment author: Peter_de_Blanc 30 January 2010 10:50:03PM 2 points [-]

It seems that you think "complex" means "difficult." It doesn't. Complex means "requires a lot of information to specify." There are no simple problems with complex solutions, because any specification of a problem is also a specification of its solution. This is the point of my original post.

Comment author: timtyler 30 January 2010 11:39:12PM 2 points [-]

So: a galaxy-conquering civilisation has low Kolmogorov complexity - because it has a short description - namely "a galaxy-conquering civilisation"???

If you actually attempted to describe a real galaxy-conquering civilisation, it would take a lot of bits to specify which one you were looking at - because the method of getting there will necessarily have involved time-and-space constraints.

Those bits will have come from the galaxy - which is large and contains lots of information.

More abstractly, "Find a root of y = sin(x)" is a simple problem with many K-complex solutions. Simple problems really can have K-complex solutions.

Comment author: Peter_de_Blanc 31 January 2010 12:10:46AM *  2 points [-]

A particular galaxy-conquering civilization might have high Kolmogorov complexity, but if you can phrase the request "find me a galaxy-conquering civilization" using a small number of bits, and if galaxy-conquering civilizations exist, then there is a solution with low Kolmogorov complexity.

Hmm, okay. I should not have said "there are no simple problems with complex solutions." Rather, there are no simple problems whose only solutions are complex. Are we in agreement?

Comment author: CronoDAS 01 February 2010 02:00:43AM *  4 points [-]

Joke counterexample:

x^2 = -1 is a simple problem that only has complex solutions. ;)

(Of course, that's not the meaning of "complex" that you meant.)

Serious counterexample:

The four-color theorem is relatively simple to describe, but the only known proofs are very complicated.

Comment author: wedrifid 01 February 2010 03:05:48AM 7 points [-]

Gah, don't over-qualify jokes! It's a supplicating behavior and seeking permission to be funny blunts the effect. Just throw the "X^2 = -1" out there (which is a good one by the way) and then go on to say "A more serious counterexample". That's more than enough for people to 'get it' and anyone who doesn't will just look silly.

This is the Right (Wedrifid-Laughter-Maximising) thing to do.

Comment author: CronoDAS 01 February 2010 03:56:42AM *  2 points [-]
Comment author: Zack_M_Davis 01 February 2010 04:18:00AM 2 points [-]

Was that a practical joke on wedrifid?

Comment author: CronoDAS 01 February 2010 04:28:25AM 5 points [-]
Comment author: wedrifid 01 February 2010 05:54:13AM *  1 point [-]

Nice. Die. :P

Comment author: Jordan 01 February 2010 02:10:21AM 1 point [-]

But that complicated proof could be concisely provided via a universal proof algorithm and the statement of the four color theorem.

Comment author: Peter_de_Blanc 01 February 2010 05:47:52AM 0 points [-]

Exactly! The Kolmogorov complexity is not very high.

Comment author: timtyler 31 January 2010 12:29:58AM 1 point [-]

I am not sure.

How about: what is the smallest number that can't be described by an English sentence of less than ten thousand words? ;-)

Of course, knowing that a K-simple solution existed in the form of the problem specification would not help very much in constructing/implementing it.