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Distributed.net Finds Optimal 25-Mark Golomb Ruler

kpearson writes "Distributed.net's 8-year-old OGR-25 distributed computing project has just proven conclusively that the predicted shortest 25-mark Golomb ruler is optimal. 'The total length of the ruler is 480, with marks at positions: 0 12 29 39 72 91 146 157 160 161 166 191 207 214 258 290 316 354 372 394 396 431 459 467 480. (This ruler may alternatively be expressed in terms of the distance between those positions, which is how dnetc displays them: 12-17-10-33-19-...).' 124,387 people participated in the project and two people found the shortest ruler, one on October 10, 2007 and the other on March 24, 2008."

17 of 265 comments (clear)

  1. wtf by Anonymous Coward · · Score: 5, Insightful

    i know we're all supposed to be nerds here, but this is way left of field. dont supposed you could have included a LITTLE more info in the summary as to what the fuck you're talking about?

    1. Re:wtf by Anonymous Coward · · Score: 5, Informative

      According to the wikipedia article that was linked, a Golomb ruler is a set of numbers where no two pairs of numbers have the same distance. The "order" is how many numbers are in it, and the "optimal" ruler for an order is the one that ends on the lowest number.

      So what they've found which set of 25 numbers - where the distance between any possible pair among them is unique - ends on the lowest number.

  2. Re:proved? by martin-boundary · · Score: 5, Insightful

    Did I fail math class?

    Yes. Yes, you did.

  3. Re:proved? by bunratty · · Score: 5, Informative

    You're thinking of science. You can only disprove a hypothesis, never prove it true. In math, you can prove or disprove a conjecture.

    --
    What a fool believes, he sees, no wise man has the power to reason away.
  4. Re:proved? by philspear · · Score: 5, Funny

    But you can't prove that, which proves his point.

  5. Re:proved? by Anonymous Coward · · Score: 5, Informative

    What most people don't realize is that all of mathematics is based on certain assumptions, alternatively called axioms, postulates or definitions. Do all triangles have interior angles that add up to 180 degrees? Yes, but only if you make certain assumptions. That's called Euclidean geometry. There is also non-Euclidean geometry which is equally valid and is used to describe some systems in reality. Is there no highest prime? Does 2 + 2 = 4? Do parallel lines never intersect? Are no circles square? Yes again on all counts, but only if you make certain assumptions. So when we say that "x is proven" in mathematics then that is really shorthand for "x is proven based on certain assumptions". That doesn't stop some overzealous mathematicians from acting a little bit smug. I would like to point all smug mathematicians to Kurt Godel's incompleteness theorems.

  6. Re:Story by Raenex · · Score: 5, Insightful

    why the hell is everything tagged "story"?

    I have another question. What happened to the option to turn off tags?

    And one more: Is there any forum to discuss Slashdot issues? Seems like the only way is to bitch off-topic in the articles.

  7. Hello, context??? by schamberlin · · Score: 5, Insightful

    That's got to be the most incomprehensible story summary I've ever seen posted to Slashdot, and that's saying a lot. Seriously. The predicted shortest 25-mark Golomb ruler is optimal? What on earth are you talking about? How about giving us the barest minimum of a context, so we might have some tiny clue what that spew of buzzwords is getting at.

    1. Re:Hello, context??? by glwtta · · Score: 5, Insightful

      we should be eager to find out, and competent enough to take the simple step necessary to do so

      Oh get off it. It's not about being "spoonfed", it's about writing a decent summary. When mentioning a relatively obscure topic (yes, yes, all real geeks know what a Golomb ruler is, etc) it's pretty much common sense to throw in a one-sentence description (so we at least know the general context), instead of, say, a useless list of numbers. I don't need you to tell me what I'm supposed to be eager to do, thank you very much.

      As far as complaining goes, given that:
      - that was a bad summary
      - it is the job of an editor to improve on bad summaries
      - Slashdot does have editors

      It is at least theoretically possible that complaining can accomplish something. Theoretically.

      --
      sic transit gloria mundi
  8. Re:It hasn't been proven, it has been shown. by gardyloo · · Score: 5, Insightful

    Yes, people routinely get this wrong. They're not wrong this time.

      In this case, the distinction between "it was proven" and "it was shown" is a distinction without a difference. In math, you can "show" something within a restricted domain; for example, that a postulated solution to a given equation really is a solution, without giving a complete family of solutions. One can show it numerically, or show it analytically. Here, a restricted set of postulated solutions over the only available domain (the positive integers) was exhaustively searched for actual solutions, and the set that satisfied the postulates was also shown to be optimal (in a well-defined sense for the problem).

        This is no more a "non-proof" than the proof of the 4-color map theorem in two dimensions, which was also "shown" using an exhaustive search.

  9. Re:cool! by Dermah · · Score: 5, Funny

    I was expecting you to measure the shit with a Golomb ruler. Oh well.

  10. Why the hell does Gollum need a ruler anyway? by unassimilatible · · Score: 5, Funny

    The sumbitch spends most of his time in a dark cave.

    And what the hell would he measure anyway? Not like he has any windows for drapes, my precious.

    --
    Slashdot "libertarians": Small government for me, big government for those I disagree with. -1, I disagree with you
  11. Re:Story by Todd+Fisher · · Score: 5, Funny

    A forum!? You can take your fancy Web 2.0 "community" fad elsewhere. We've got Golomb rulers to discuss here!

    --


    --I'm not talking about dance lessons. I'm talking about putting a brick through the other guy's windshield.-
  12. Re:Story by _xeno_ · · Score: 5, Informative

    why the hell is everything tagged "story"?

    If you mouse over it (and have JavaScript enabled), you'll be informed that it's the "type tag." I assume the concept is that it differentiates between journals, comments, bookmarks, feed entries, and other types of nodes that could, conceptually, appear in the firehose.

    I have no idea why Slashdot feels the need to show these on the main page, though, considering that everything that currently shows on the main page is a story. But if you play with the firehose, it's what tells you what "thing" the entry is.

    --
    You are in a maze of twisty little relative jumps, all alike.
  13. Re:Story by Zadaz · · Score: 5, Insightful

    Is there any forum to discuss Slashdot issues? Seems like the only way is to bitch off-topic in the articles.

    No, you can directly email them but of course they will only use that as ammunition to be taken out of context and savaged via the poorly conceived "Disagree Mail" "Feature".

    I'd leave, but there isn't really an alternative that's better. Instead I use adblock and suck off this teat without providing benefit to the site. (Unless you include this post as "providing benefit" which is dubious since it will almost certainly get modded down.)

  14. Re:can someone please tell me which #s aren't incl by JustOK · · Score: 5, Funny

    a few lines from Python would say

    Then shalt thou count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out.

    --
    rewriting history since 2109
  15. Re:Story by glwtta · · Score: 5, Funny

    If you mouse over it (and have JavaScript enabled), you'll be informed that it's the "type tag."

    Actually, when I mouse over tags I get an incomprehensible mess of overlapping elements. It's probably my fault for using something as obscure as Firefox, though; I'm sure it works perfectly on IE6.

    --
    sic transit gloria mundi