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The P=?NP Poll (2002) [pdf]

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Re: The P=?NP Poll (2002) [pdf]

#51
post #24
post #17

Earlier quoted context omitted.

This argument is useless since polynomial time is just as intractable as exponential time if the exponent is large. For example, lets say that we found a way to solve all np problems in n^1000 time, would that change anything? No, there aren't even 2^1000 atoms in the universe so we will only be able to solve it for the case n=1.

Your argument supports the view that P is a useless concept, not that that argument is pointless.

Often a "proof" that P does not equal NP is that it would be terribly inconvenient if solvable in n to the second or whatever, and therefore in a sort of cosmic censorship saves us by claiming it clearly can't be the case because it would be so annoying.

A good argument can be provided by an analysis of statistical thermodynamics gas laws. It highly disturbs some people to think that atoms being in motion implies that all the oxygen atoms in the room air might coincidentally cluster into a small corner of the room leaving the victim to suffocate. There is no reason to think that impossible under most thermodynamics theories. However, it is nearly infinitely unlikely and you'd merely have to wait a ten to the hundred times the lifespan of the universe for it to coincidentally happen. I suppose it scales quite strongly with room volume and linearly with air pressure, you have one atom in the ISS airlock and being in one half the air lock at any given moment is a very predictable 50:50 odds...

Likewise if the smallest polynomial solution to a NP problem takes a google's worth of universes to calculate, then even if it is poly you need not worry too much about mere human inconvenience.

I'm not saying its a wise way to go thru life, but there exists a large set of people who get hung up on whats convenient or beautiful must be right, even if whats right turns out to be very ugly or inconvenient, so for them "P=NP but your bank account is still secure" is a very big deal.

Re: The P=?NP Poll (2002) [pdf]

#52

#8 is a fun one (some of these answers are half-joking): "Proof by contradiction. Assume P = NP. Let y be a proof that P = NP. The proof y can be verified in polynomial time by a competent computer scientist, the existence of which we assert. However, since P = NP, the proof y can be generated in polynomial time by such computer scientists. Since this generation has not yet occurred (despite attempts by such computer…

Is that true -- that the proof (if we produce one) will be verifiable in polynomial time?

It is not really meaningful to talk about a single instance being verifiable in polynomial time.

Re: The P=?NP Poll (2002) [pdf]

#53

#8 is a fun one (some of these answers are half-joking): "Proof by contradiction. Assume P = NP. Let y be a proof that P = NP. The proof y can be verified in polynomial time by a competent computer scientist, the existence of which we assert. However, since P = NP, the proof y can be generated in polynomial time by such computer scientists. Since this generation has not yet occurred (despite attempts by such computer…

Is that true -- that the proof (if we produce one) will be verifiable in polynomial time?

Technically, yes, but practically, no.

THEOREMS (the language of correct proofs) is in P; given a correct proof (possibly restricted to being in first-order logic), it can be verified in polynomial time. In the first-order logic case, all you have to do is read the proof from beginning to end and verify that each statement follows from either an axiom or an already-established statement. This is done entirely syntactically, requiring no knowledge of the underlying mathematics.

However, to do this requires formalizing the entire proof in machine-checkable format, which is a substantial undertaking even for relatively simple proofs and will likely take far longer than polynomial time.

Re: The P=?NP Poll (2002) [pdf]

#54

#8 is a fun one (some of these answers are half-joking): "Proof by contradiction. Assume P = NP. Let y be a proof that P = NP. The proof y can be verified in polynomial time by a competent computer scientist, the existence of which we assert. However, since P = NP, the proof y can be generated in polynomial time by such computer scientists. Since this generation has not yet occurred (despite attempts by such computer…

Is that true -- that the proof (if we produce one) will be verifiable in polynomial time?

As petters points out, "X time" has no useful meaning here.

An interesting and still valid point, however, is that P=NP may be undecidable (in the sense of Gödel's incompleteness theorem). In other words, our current axioms may be insufficient to prove or disprove P=NP.

http://www.scottaaronson.com/papers/pnp.pdf

> P != NP is either true or false. It’s one or the other. But we may not be able to prove which way it goes, and we may not be able to prove that we can’t prove it.

Re: The P=?NP Poll (2002) [pdf]

#55
Not a lot of mention of AI for CS, even in 2002. What about (2080+, P/=NP, proof techniques completely opaque to humans). And by that I don't mean mechanical exclusion of special cases like for map-coloring. As mentioned already, there's like a handful of people that understand the FLT proof, that situation is unlikely to improve.

Re: The P=?NP Poll (2002) [pdf]

#56
post #46

Earlier quoted context omitted.

Yes, I think it is like that.

Another way to enumerate oracles is to consider the set of terminating Turing machines (and enumerating them is itself uncomputable but whatever). Each TM corresponds to an oracle that computes its result in O(1).

This is not true. You can have oracles for uncomputable problems, like oracle for the halting problem.

Re: The P=?NP Poll (2002) [pdf]

#57
post #37

A really cool result which seems relatively unknown is that if we augment our Turing machines with an oracle X chosen uniformly at random from all oracles then P^X =/= NP^X with probability 1. An oracle is a black box that can solve a particular decision problem in O(1). The notation means e.g. P^SAT = class of all problems that can be solved in P time with a machine that has an oracle for SAT. It gets really ingesti…

What does it mean to take a random oracle from all oracles? How do you enumerate oracle-space? Is that something like the space of all problems, where each problem corresponds to an oracle for that problem?

You can choose a random oracle by choose a language by random. Here a language means a set of strings.

Re: The P=?NP Poll (2002) [pdf]

#58
post #52

Earlier quoted context omitted.

Is that true -- that the proof (if we produce one) will be verifiable in polynomial time?

It is not really meaningful to talk about a single instance being verifiable in polynomial time.

Well I was open to evidence that applies generally, but sure.

Re: The P=?NP Poll (2002) [pdf]

#59
For those that do not have time to read the whole thing, #29 is worth quoting:

"Stuart Kurtz (University of Chicago, 2050, P!=NP) [on wether and when proof will be found]:

Knowing Ketan Mulmuley, I live in fear that the solution will be via algebraic geometry, and it will come soon enough that I’ll be expected to understand it. An alternative nightmare is that the undergraduate who solves it will publish his solution in French."

But it is by far not the only funny opinion in this paper.

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