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posted by janrinok on Sunday March 02 2014, @08:30PM   Printer-friendly [Skip to comment(s)]
from the keeping-geeks-and-mathematicians-happy dept.

KritonK writes:

Ed's Note: For those not sure what an optimal Golomb ruler is, or how you would use one, see here.

"Following the recent start of the OGR-28 project, the search for the optimal Golomb ruler with 28 marks, distributed.net quietly announced the completion of project OGR-27 on February 25. The shortest Golomb ruler with 27 marks has length 553 and marks at positions 0 3 15 41 66 95 97 106 142 152 220 221 225 242 295 330 338 354 382 388 402 415 486 504 523 546 553. This confirms that the best known, up to now, Golomb ruler was optimal. When the project began, it was expected that a shorter ruler would be found, but this did not happen."

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OGR-28 Project has Begun 31 comments

KritonK writes:

"On February 19, distributed.net began project OGR-28, the challenge to discover the Optimal Golomb Ruler with 28 marks. The previous challenge, OGR-27, is almost complete, with only 9 stubs remaining to be processed, as of February 19. People participating in that challenge do not need to update their client, as it can also process stubs for the new challenge."

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  • (Score: 5, Funny) by Appalbarry on Sunday March 02 2014, @08:43PM

    by Appalbarry (66) on Sunday March 02 2014, @08:43PM (#9729) Journal

    Man, I can't recall how many times I was reading Slashdot, and thought to myself, "Where are the updates on Golomb ruler research?"

    Actually, I've been pretty amazed at the quality of what gets posted to SN - smart, interesting stuff, a lot of which I would never have seen.

    Now, imagine a Beowolf cluster of Golomb rulers!

    • (Score: 3, Interesting) by VLM on Sunday March 02 2014, @09:28PM

      by VLM (445) Subscriber Badge on Sunday March 02 2014, @09:28PM (#9747)

      "Now, imagine a Beowolf cluster of Golomb rulers!"

      That would just be a big pile of varying length rulers ... two of which (reversed) are shortest, aside from some really small ones where there are even number of duplicates all the same short length. Boring.

      I would be amazed if a zillion years from now someone discovered OGR-75 is a triple or something like that. Want to impress the local extraterrestrials with your math abilities? Send them a really long list of OGRs. I don't remember any proofs about OGR duplicates. Maybe no long ones exist only short.

      A cluster of Optimal GR would vaguely resemble a radio telescope array or whatever else they're being used for now.

      I always thought a funny ardweeeeeeeeeeenio project would be a real world OGR-15 with LEDs on the correct centimeter spaces (it'll be about 5 feet long?) and a display and dial and you dial up "hey OGR-15 gimmie 9 cm" and it'll figure out which two LEDs to illuminate to provide you with 9 cm, assuming it exists (no perfect rulers exist beyond some short length, I think?). In my infinite spare time of course. That would obviously be an incredibly handy ruler for the machine shop, which I'm sure I would use daily.

      • (Score: 1) by egcagrac0 on Sunday March 02 2014, @10:29PM

        by egcagrac0 (2705) on Sunday March 02 2014, @10:29PM (#9785)

        Most LEDs I see aren't small enough to be useful as ruler ticks.

        Laser emitters have potential, but aligning them all to parallel would be a pain.

        Two lasers with two mirrors on two leadscrews, on the other hand, would allow you to dial in two arbitrary positions, limited by backlash and screw calibration (but those are already commonly addressed in a machine shop).

        • (Score: 2) by VLM on Sunday March 02 2014, @10:36PM

          by VLM (445) Subscriber Badge on Sunday March 02 2014, @10:36PM (#9790)

          Yeah but that wouldn't be an OGR application. I was aiming at more of an educational "science fair demonstration" kind of thing. Ahhh I see how it works by turning the dial to select different lengths type of thing.

          • (Score: 1) by egcagrac0 on Monday March 03 2014, @12:25AM

            by egcagrac0 (2705) on Monday March 03 2014, @12:25AM (#9834)

            Absolutely true. It's a valid visualization tool, but not a practical application.

            A practical application of such a system would be for, say, current transformers, or a resistance substitution box.

    • (Score: 0) by neagix on Sunday March 02 2014, @10:11PM

      by neagix (25) on Sunday March 02 2014, @10:11PM (#9768)

      before the Beowulf cluster mention, I was buying it that you were serious..

  • (Score: 5, Informative) by Barrabas on Sunday March 02 2014, @09:02PM

    by Barrabas (22) on Sunday March 02 2014, @09:02PM (#9736) Journal

    I was involved with this a looong time ago - right after the Scientific American article appeared in, let's see here, March 1972.

    Back then we were happy to find rulers of length 12 (IIRC). It's a hard problem - there would be considerable interest if someone can come up with a better algorithm.

    • (Score: 1) by hubie on Monday March 03 2014, @03:38AM

      by hubie (1068) Subscriber Badge on Monday March 03 2014, @03:38AM (#9891) Journal

      What is the general algorithm? If you are confirming it is optimal only by exhausting all the other configurations, it sounds like you need to brute-force it.

  • (Score: 0, Interesting) by Anonymous Coward on Sunday March 02 2014, @09:54PM

    by Anonymous Coward on Sunday March 02 2014, @09:54PM (#9759)
  • (Score: 0) by EvilJim on Sunday March 02 2014, @10:10PM

    by EvilJim (2501) on Sunday March 02 2014, @10:10PM (#9767) Journal

    this is a ruler made of parts of dead people?

  • (Score: 1) by rev_irreverence on Sunday March 02 2014, @10:56PM

    by rev_irreverence (144) on Sunday March 02 2014, @10:56PM (#9802)

    Distributed.net's Optimal Golomb Ruler projects first started in February 2000 with the search for a more optimal 24 mark ruler (OGR-24). Since then they have exhaustively searched for a more optimal 25, 26, and 27 mark ruler. It took 14yrs of searching to complete those projects and they have just started the search for a 28 mark ruler.

    In those 14 years not a single project has successfully found a "more" optimal ruler than what was previously known. Rather they have just managed to confirm that the previously known shortest ruler is already the "most" optimal.

    Seems like a massive expenditure of CPU cycles for not a lot of results. I have been participating in these projects for over a decade, but I am seriously reconsidering getting involved in OGR-28.

    Any ideas for other distributed computing projects?

    • (Score: 4, Insightful) by guises on Monday March 03 2014, @04:50AM

      by guises (3116) on Monday March 03 2014, @04:50AM (#9908)

      Well there's always Folding@Home, and it's had some successes, but all of these projects are doing basic research, and if you're looking for exciting results, basic research is not where you'll find them.

    • (Score: 0) by Anonymous Coward on Monday March 03 2014, @05:59AM

      by Anonymous Coward on Monday March 03 2014, @05:59AM (#9918)

      Well the OGR project at least adds something (however small) to our knowledge. Compare that to dnet's RC5 projects. (And think of all the electricity used to mine bitcoins...)

    • (Score: 2, Informative) by wonkey_monkey on Monday March 03 2014, @07:39AM

      by wonkey_monkey (279) on Monday March 03 2014, @07:39AM (#9942) Homepage

      Folding@home. While I can appreciate the pure mathematics of Golomb Rulers, I'd think that contributing to the advancement of medical science might be more useful in the long run.

      --
      systemd is Roko's Basilisk
    • (Score: 0) by Anonymous Coward on Monday March 03 2014, @06:42PM

      by Anonymous Coward on Monday March 03 2014, @06:42PM (#10151)

      A quick search would have found this

  • (Score: 2, Funny) by mcgrew on Monday March 03 2014, @02:32AM

    by mcgrew (701) <publish@mcgrewbooks.com> on Monday March 03 2014, @02:32AM (#9877) Homepage Journal

    Slide rules FTW!

    --
    Free Martian whores! [mcgrewbooks.com]