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Math Supercomputing Science

Distributed.net Finds Optimal 25-Mark Golomb Ruler 265

Posted by timothy
from the unique-and-in-duplicate dept.
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."
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Distributed.net Finds Optimal 25-Mark Golomb Ruler

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  • wtf (Score:5, Insightful)

    by Anonymous Coward on Saturday October 25, 2008 @09:35PM (#25513693)
    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?
  • Re:proved? (Score:5, Insightful)

    by martin-boundary (547041) on Saturday October 25, 2008 @09:55PM (#25513823)

    Did I fail math class?

    Yes. Yes, you did.

  • Re:proved? (Score:5, Insightful)

    by gardyloo (512791) on Saturday October 25, 2008 @10:01PM (#25513855)

    Mathematics may be defined
    as the subject in which we
    never know what we are talking
    about,nor whether what we are
    saying is true.
    --Bertrand Russell

  • Re:wtf (Score:0, Insightful)

    by Anonymous Coward on Saturday October 25, 2008 @10:09PM (#25513921)

    Click on the 4th link?

  • by ClintJCL (264898) <clintjcl+slashdot&gmail,com> on Saturday October 25, 2008 @10:12PM (#25513931) Homepage Journal
    The Wikipedia page says One practical use of Golomb rulers is in the design of phased array radio antennas such as radio telescopes. Antennas in an [0,1,4,6] Golomb ruler configuration can often be seen at cell sites [wikipedia.org]. Does this mean we can now construct larger antennas with greater sensing power, using fewer materials, due to knowing a larger optimal configuration than previously?
  • by mblase (200735) on Saturday October 25, 2008 @10:19PM (#25513991)

    Does this mean we can now construct larger antennas with greater sensing power, using fewer materials, due to knowing a larger optimal configuration than previously?

    Probably not, since (a) optimal rulers of order greater than four but less than twenty have been known for some time, and (b) the [0,1,4,6] ruler is proven to be the largest perfect optimal ruler (according to the Wikipedia article).

  • Re:Story (Score:5, Insightful)

    by Raenex (947668) on Saturday October 25, 2008 @10:19PM (#25513995)

    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.

  • Shouldn't have to (Score:5, Insightful)

    by ArchieBunker (132337) on Saturday October 25, 2008 @10:23PM (#25514019) Homepage

    Headlines or summaries should be self explanatory.

  • Hello, context??? (Score:5, Insightful)

    by schamberlin (1354695) on Saturday October 25, 2008 @10:34PM (#25514103)

    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.

  • by schamberlin (1354695) on Saturday October 25, 2008 @10:41PM (#25514149)

    In your example, the distance between 0 and 3 is the same as between 3 and 6. Not a Golomb ruler.

  • by Pretzalzz (577309) on Saturday October 25, 2008 @10:47PM (#25514185)
    Well, 25 choose 2 is 300 so presumably 180 numbers must be missing.
  • by gardyloo (512791) on Saturday October 25, 2008 @10:54PM (#25514243)

    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.

  • Re:proved? (Score:2, Insightful)

    by panda cakes (1333537) on Saturday October 25, 2008 @10:55PM (#25514245)
    You are confused - there are no assumptions in mathematics because mathematics does not deal with any real entities. There are only definitions and what you are talking about applies to them: depending on your definitions properties of defined entities will differ. Quite a trivial conclusion most sane people already realize.
  • Bah, Humbug! (Score:5, Insightful)

    by Main Gauche (881147) on Saturday October 25, 2008 @11:02PM (#25514303)

    There is a BIG difference between [proven and shown] as anyone within the Maths and the Sciences can tell you. I'm sorry, but people routinely get this wrong and it gets quite aggravating.

    First, there is such a thing as proof by inspection. It may be considered inelegant by certain folks, but it's there nonetheless.

    Second, it's just as aggravating (for those in certain fields) that computational results are not more valued. Sure, analytical results provide insight that computational results do not. But if you simply want to know the answer, why not accept a computational result?

    Third, anticipating the old "how do we know the computer didn't make a mistake" comment: Theoretical proofs need to be proofread just as code does. So why not accept a computer program (and its verified output, as in the summary) as proof?

  • by Anonymous Coward on Saturday October 25, 2008 @11:09PM (#25514337)
    You really can't get more specific than that. Just because you don't know what a Golomb ruler isn't doesn't make it a bad summary. A summary has to assume some understanding of the subject at hand. If a summary includes mention of a photon, for example, it doesn't necessarily require that it be defined what a photon is in the summary.
  • Re:proved? (Score:3, Insightful)

    by Futile Rhetoric (1105323) on Saturday October 25, 2008 @11:24PM (#25514447)

    Hasn't GÃdel done pretty much exactly that? [wikipedia.org]

  • by Galactic Dominator (944134) on Saturday October 25, 2008 @11:28PM (#25514475)

    A summary has to assume some understanding of the subject at hand. If a summary includes mention of a photon, for example, it doesn't necessarily require that it be defined what a photon is in the summary.

    That's the point of the criticism. A large majority of the readers here would be familiar with a photon, but not with a Golomb ruler.

  • Re:wtf (Score:1, Insightful)

    by Anonymous Coward on Sunday October 26, 2008 @12:08AM (#25514663)
    take note editors. it would not have been difficult to include something along the lines of the OPs first paragraph to make the summary read like an article, instead of a steaming pile of shit
  • by frieko (855745) on Sunday October 26, 2008 @12:17AM (#25514711)
    Sure, but since there's a Wikipedia link right in the summary that does a wonderful job explaining it, this is just a simple case of RTFA.
  • Re:Story (Score:5, Insightful)

    by Zadaz (950521) on Sunday October 26, 2008 @12:45AM (#25514829)

    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 [slashdot.org]" "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.)

  • by DAldredge (2353) <SlashdotEmail@GMail.Com> on Sunday October 26, 2008 @01:09AM (#25514953) Journal
    If you don't know what one is google the damn thing.
  • Re:What (Score:2, Insightful)

    by Arch24 (1091167) on Sunday October 26, 2008 @01:40AM (#25515101)
    116 comments and none have yet explained what the article is actually talking about. Thanx for nothing /. All I want is a little clarity plz. =)
  • RC5-72 (Score:5, Insightful)

    by epine (68316) on Sunday October 26, 2008 @02:01AM (#25515187)

    It's worth calculating the number of gigawatt-hours of electricity is expended on these toy problems. The original goal was to make a political point: we can't assume some of these codes are out of range with present technology. Having made your point, you're just boiling water to arbitrarily make the problem another order of magnitude more expensive to crack.

    When did we decide that the major problem facing planet earth was a surplus of electricity we must burn off by any available method?

  • by glwtta (532858) on Sunday October 26, 2008 @03:03AM (#25515385) Homepage
    Sure, but since there's a Wikipedia link right in the summary that does a wonderful job explaining it, this is just a simple case of RTFA.

    So, to understand the summary, and therefore decide whether or not I want to RTFA, I need to RTFA? You see where that defeats the purpose of the summary?
  • by Toonol (1057698) on Sunday October 26, 2008 @03:48AM (#25515603)
    This is Slashdot, we're supposed to be intelligent here. This means that while we may not know what a Golomb ruler is, we should be eager to find out, and competent enough to take the simple step necessary to do so... not complain that we aren't being spoonfed gently enough (even though posting that complaint takes more effort than the required click to actually find out).
  • by glwtta (532858) on Sunday October 26, 2008 @04:18AM (#25515705) Homepage
    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.
  • by steevc (54110) on Sunday October 26, 2008 @05:24AM (#25515929) Homepage Journal

    I ran OGR25 again for the last few months in hope of seeing that project complete. RC5-72 just seems pointless to me. We already know it will take decades without some radical improvement in processing power.

    I've been disappointed by the lack of updates to the dnet site. Even now the projects page still says that OGR25 is active.

    I've moved to Folding@home now as I hope it will have tangible benefits. My contribution is pretty minor as I don't have the hardware for GPU processing.

  • Precisely! (Score:4, Insightful)

    by rbarreira (836272) on Sunday October 26, 2008 @08:36AM (#25516757) Homepage

    Exactly... I participated in RC5-64, but RC5-72 just seems pointless to me. It's the exact same problem, just 256 times harder.

    Furthermore, these encryption challenges are not actually discovering anything. They're essentially brute-forcing a random number which another computer chose.

    Contrast this with distributed computing challenges about mathematics (such as OGR-25 which is being discussed here), health or other issues where the result is something meaningful and potentially useful about the world.

  • by rbarreira (836272) on Sunday October 26, 2008 @12:31PM (#25518129) Homepage

    According to this page [pcstats.com], the same PC I mentioned before uses up 40 more watts when under full load than when idling. That's about 27% of the 150 watts I mentioned before.

    These figures are just ballpark numbers which give a rough idea. There are all kinds of people running these programs... Some make computer farms specifically to run them, some others don't buy new computers but leave theirs when they otherwise wouldn't, and then there's those who don't change their habits because of distributed computing. There's everything in between as well, making it very hard to estimate the real impact.

  • by unassimilatible (225662) on Sunday October 26, 2008 @03:42PM (#25519683) Journal
    The difference is of course, that Apple and MS are not people.

    Corporations are investment vehicles for people. They represent the interests of people. These people are called "stockholders." This is how the average Joe (70% of US equities are held by the small investor) can pool his resources with other people and get part of the Dream. Like my parents. My dad is a former middle class salesman who was "retired" early due to an on-the-job disability. Thankfully, my parents got into Apple at a good price, and the stock has been a stellar performer for their golden years.

    Although personally, I'm not particularly statist about Apple and Microsoft. I just wish they would stop being cunts.

    Now, if only other people like yourself would understand that corporations are not, in fact, entities in and of themselves, but represent the interests of stockholders. Not employees, not customers, not Slashdotters who don't believe in patent or copyright, but the interests of those who entrusted their money to the corporation. So keep your hands and laws and regulations off of other peoples' money, if you please. If you don't like the iTunes DRM, don't buy an iPod.

    You are entitled to your opinion, but at least understand why Apple does the things it does - to increase shareholder value. And they do it well. So please don't tell other people how their business should be run. Go invest your money with Red Hat or something, or buy an open-source media player. But disparaging Apple because it doesn't do what you want is like being mad at your neighbor's wife because she doesn't make you dinner at night. It's not her job. And if she makes your neighbor great dinners that you have to smell every night, don't be a hater; congratulate your neighbor on finding a great wife. Then go find one that meets your needs. Because the relationship between your neighbor and his wife is none of your goddamned business!
  • Re:wtf (Score:2, Insightful)

    by kpearson (760708) on Sunday October 26, 2008 @04:28PM (#25520079) Homepage

    Pfff, 25-mark. Wake me up when they get the 26-mark. </unimpressedslashdotuser>

    Instead of sleeping, why not help them find it [distributed.net]?

  • by timbck2 (233967) <<moc.liamg> <ta> <2kcbmit>> on Monday October 27, 2008 @09:43AM (#25526289) Homepage

    You really can't get more specific than that. Just because you don't know what a Golomb ruler isn't doesn't make it a bad summary. A summary has to assume some understanding of the subject at hand.

    However, for anything written (summary, abstract, article, etc.) the audience should be considered, and the appropriate degree of explanation presented.

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