Live data from Hacker News

The polynomial algorithm for 3-SAT problem (or P=NP)

romvf.wordpress.com

81–90 of 156 posts

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#81
post #74
post #71

Earlier quoted context omitted.

Here is one proof. I don't know if this can be attributed to Ramanujan. Let a, b be equal integers a = b a^2 = ab // multiply by a a^2 + a^2 - 2ab = ab + a^2 - 2ab // subtract a^2 - 2ab 2(a^2 - ab) = a^2 - ab 2 = 1 From p319, Fermat's Last Theorem by Simon Singh

division by zero ?

A contradiction implies all falsehoods are true.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#82

Earlier quoted context omitted.

To pick on a small part of your comment: Do any theoretical computer scientists seriously worry that a proof that P=NP would threaten cryptography? It's not like a proof would suddenly make an i7 able to factor huge numbers in polynomial time. Also, while all polynomial-time algorithms are considered "tractable" in theoretical CS, that doesn't mean that they're all practical on current hardware (nor does it claim to…

Factoring is in NP. Proving that P=NP would, by definition, imply that large numbers can be factored in polynomial time. The issue of whether it's a feasible amount of work is exactly what I was addressing.

Speaking pedantically, P is in NP also. I suspect that NP is being used as shorthand for NP-complete, not just NP. As for actual deterministic factorization Wikipedia says that

'It is suspected to be outside of all three of the complexity classes P, NP-complete, and co-NP-complete'

So even if this showed 'P = NP-complete' it may not imply imply factorization is in P. I'm at the limits of my rusty complexity knowledge here so if any knows better please correct me.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#83

Earlier quoted context omitted.

It's on the arXive, so you know it's legit.

Just because its on arXiv doesn't mean its legitimate. Its more likely that it is legitimate if it gets published (with a few exceptions like the Poincaré conjecture.

http://www.sarcasmsociety.com/irony/howtorecognizeirony

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#85
tl,dr version of his strategy (as far as I understood it)

1. For a fixed permutation construct a Viterbi-like search on the triplet assignments - if it fails it is not satisfiable. However, if it doesn't fail right away, there is still no guarantee there is an assignment. Call this structure compact triplet (CTF) or whatever.

2. Constuct a small set of permutation (at most m) for which every clause in the original CNF failing to satisfy will mean that at least one of these permutations CTFs will fail to satisfy.

3. Efficiently? combine the structures.

I didn't really read it deeply but that from what I understood that seems to be the top level strategy. I'm not 100% certain about it.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#86
post #82

Earlier quoted context omitted.

Factoring is in NP. Proving that P=NP would, by definition, imply that large numbers can be factored in polynomial time. The issue of whether it's a feasible amount of work is exactly what I was addressing.

Speaking pedantically, P is in NP also. I suspect that NP is being used as shorthand for NP-complete, not just NP. As for actual deterministic factorization Wikipedia says that 'It is suspected to be outside of all three of the complexity classes P, NP-complete, and co-NP-complete' So even if this showed 'P = NP-complete' it may not imply imply factorization is in P. I'm at the limits of my rusty complexity knowledge…

Actually, cperciva is right here. Factoring is in NP, therefore if P=NP then there is a polynomial-time algorithm for factoring. Many problems harder than NP are NP-complete, so saying factoring is in NP-complete would not imply the conclusion.

Also, there are problems in NP that are neither in P, nor are they NP- or co-NP-complete.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#87

I'm not at all an expert on this material, but some random points to get people started: 0. This guy looks orders of magnitude less looney than the usual P=NP prover. I hope someone who knows this material well steps in soon. 1. This guy has implemented his algorithm. This is a very good sign -- most garbage "algorithms" are exposed to be broken when people try to implement them. 2. Most 3SAT problems are "easy". Bei…

To pick on a small part of your comment: Do any theoretical computer scientists seriously worry that a proof that P=NP would threaten cryptography? It's not like a proof would suddenly make an i7 able to factor huge numbers in polynomial time. Also, while all polynomial-time algorithms are considered "tractable" in theoretical CS, that doesn't mean that they're all practical on current hardware (nor does it claim to…

Don't forget that changing out algorithms is a time-consuming process. It's not a 10 second fix, it's a technical challenge and a bureaucratic nightmare. I mean, it takes a week's worth of meetings to restock the condiments in the mess hall in some of these places. So you wind up in a situation where it takes a year or more to implement this stuff once you have the ideal solution selected, and selecting the replacement solution takes another year or more. So even if it's not projected to be an issue for 5 years, you have to start the replacement process right away.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#88
post #75
post #40

Earlier quoted context omitted.

Yeah, and, seriously, a Russian?! Please...

Why not a Russian? For example the Russian Mathematics Olympiad is considered harder than the International Math Olympiad by many of the top contestants. Edit: why downvoting?

> Edit: why downvoting?

Please stop, you do understand.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#89
post #78
post #75

Earlier quoted context omitted.

Why not a Russian? For example the Russian Mathematics Olympiad is considered harder than the International Math Olympiad by many of the top contestants. Edit: why downvoting?

I interpreted dauphin's comment as sarcasm.

Ja, I don't like when some people refer to other people saying he "smells", that's gross. And in this case, it's also plainly false: Russians don't smell more than, say, redheads.

Re: The polynomial algorithm for 3-SAT problem (or P=NP)

#90

I'm not at all an expert on this material, but some random points to get people started: 0. This guy looks orders of magnitude less looney than the usual P=NP prover. I hope someone who knows this material well steps in soon. 1. This guy has implemented his algorithm. This is a very good sign -- most garbage "algorithms" are exposed to be broken when people try to implement them. 2. Most 3SAT problems are "easy". Bei…

Thanks for the summary with your level of competence (already a good one ;)).
Post reply on HN