Slashdot Mirror
Wiki to Help Solve Millennium Problems?
MattWhitworth writes "A new wiki has been set up over at QEDen to try to gather a community to solve the Millennium Problems. The problems are seven as yet unsolved mathematical problems that continue to vex researchers today. What do you think of this effort? Will gathering a community of people help solve problems such as P=NP, or do you think it requires a lot more than a semi-qualified community to approach the problem?"
Because social constructs already exist for current research. People don't sit in ivory towers thinking about this stuff by themselves - they go to conferences, write papers, send emails, and yes, even make wikis.
This is going to become an instructional site to teach people (hopefully correctly) what is going on in these fields, nothing more.
Did you ever notice that *nix doesn't even cover Linux?
At first glance, I'm not sure HOW this is an "unsolvable" problem. Would I not just select and group 100 students at random then rearrange the pairs as I found incompatibilities? Can someone clue me in to what I'm missing here?
... * 1. Since we're trying every possible combination, this gives us:
7 66515247971418153526438677698477539372878051288400 0
What makes a problem NP is not whether it's solvable but rather how long it takes to solve. The algorithm you propose is a search algorithm. Consider what would happen if your list of incompatible students was so large that within the group of 100 students you randomly choose, there is not a single possible arrangement of pairs. This means you would have to choose another group of 100 students. It's a minor refinement but an important one.
Now consider if that list was so large that there was only a single possible group of 100 that contains an arrangement of pairs that worked. Now consider that within that group of 100, there was only one good possible arrangement. If you're very unlucky, and you choose these set of 100 and arrangement of pairs last, you have to try every possible combination before finding the right one. Okay, so what?
Lets see how many possible answers you'd have to try. Within a group of 100 students, there are 100 choose 2 possible arrangements. There are 400 choose 100 possible choices of 100 students. n choose k is really n! / (k! (n-k)!) where n! is n * (n - 1) *
[400! / (100! 300!)] * [100! / (2! 98!)]
Your standard calculator is not going to be able to solve this one but if you have an arbitrary precision calculator (like bc), you get:
1109718121819397093151989141664840784648478532850
Which is an awfully large number. That number is so large, in fact, that even if you have a computer that could check one possible solution with every electron in the universe, until the Sun supernova's, you'd still not find the answer.
Now, that depends on really bad luck. You can construct problems though that given average luck, you would not find the solution in the lifetime of the universe. This is what cryptography is based on.
Compare this to a standard sorting algorithm. To sort the list [3, 4, 5, 6, 7, 8, 9, 2, 1, 0] given a crappy algorithm like bubble sort requires n*n = 100 computations. You can solve this problem the same way using search though. You merely have to randomly arrange the list in every possible way and check to see if your random arrangement is sorted. There are n! possible arrangements of a list of n elements so there are 10! = 3628800 possible answers to search. You can see that even a crappy algorithm like bubble sort is much better than search.
The difference is even greater with larger lists. A problem that is only solvable via search is considered NP. A problem that is solvable with an algorithm in polynomial time (n*n is a polynomial) is considered P. The N in NP stands for non-polynomial.
So the problem here is whether there exists a polynomial solution for these set of problems that we've labelled NP. What makes this even more significant is that it has been proven that if we find a polynomial solution for one NP problem, we can create solutions for any NP problem. A lot is riding on the lack of existence of a polynomail solution for NP problems. If someone where to prove that there are indeed polynomial solutions to NP problems it would be earth-shattering. After the initial shock, it would also open up a whole new world of mathematics since a lot of things we didn't think were possible to do efficiently became possible.