JoshuaZ comments on Harry Potter and the Methods of Rationality discussion thread, part 11 - Less Wrong

6 Post author: Oscar_Cunningham 17 March 2012 09:41AM

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Comment author: Eponymuse 29 March 2012 03:06:05AM 1 point [-]

Sorry, I'm really not following your pie argument. Harry would learn about the pies in the near future; since it is his style, he would think about throwing them to frighten the bullies. So, his observation of Harry+1 throwing the pies is not necessary for him to think to throw pies anyway.

What do you mean by "they don't recurse"? Surely the fact that this procedure results in fast graph isomorphism testing shows that it is not a particularly "stable" solution? Or, do fast integer factorization by writing down the first digit for the least factor greater than 1, listen as future you says "no, no, maybe," and change it to whatever, and then figure out the second digit, and so forth. The scenario you've outlined results in nearly instant integer factorization (or password guessing, or whatever), so it is probably illegal.

Comment author: JoshuaZ 29 March 2012 03:31:36AM 1 point [-]

Note that both graph isomorphism and integer factorization are problems that may well lie in P, so these aren't great examples. Traveling salesman is a bit better.

Comment author: Eponymuse 29 March 2012 01:34:45PM 0 points [-]

Sure, though my impression is that people don't think graph isomorphism actually is in P. And integer factorization turned out to be a problem for Harry. But you're right, we can actually just simulate a nondeterministic Turing machine this way: every time you have a choice for which state to visit next, just listen as future you tells you which ones not to visit.