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posted by LaminatorX on Thursday February 20 2014, @06:00PM   Printer-friendly
from the sub-optimal-rulership dept.

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, Informative) by Anonymous Coward on Thursday February 20 2014, @06:17PM

    by Anonymous Coward on Thursday February 20 2014, @06:17PM (#3613)

    So radio frequency selection to prevent intermodation interference and optimal placement of radio antennas in a phased array are just things done by dick wavers? Because golomb rulers are used for these applications.

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  • (Score: 1) by buswolley on Thursday February 20 2014, @07:07PM

    by buswolley (848) on Thursday February 20 2014, @07:07PM (#3639)

    What is the largest (most marks) ruler found?.. or does that matter for these application?
    Also, why integers? Wouldnt it be easier to create a ruler without repeating intervals if one ditched integer limitation?

    --
    subicular junctures
    • (Score: 2, Informative) by KritonK on Thursday February 20 2014, @07:28PM

      by KritonK (465) on Thursday February 20 2014, @07:28PM (#3648)

      As soon as project OGR-27 is complete (any day now) the largest known optimal Golomb ruler will have 27 marks. Till then, the largest known optimal Golomb ruler has 26 marks.

      Here [ibm.com] is a list of the shortest known Golomb rulers. The rulers of up to length 26 in that list are known to be optimal, the last three (24, 25, and 26) confirmed optimal by previous distributed.net projects. The OGR-27 project is expected to produce a shorter ruler than the one in the list. However, being pessimistic, I expect that it won't.

      • (Score: 1) by naubol on Friday February 21 2014, @04:02AM

        by naubol (1918) on Friday February 21 2014, @04:02AM (#4063)

        How do they know, they tried every permutation of numbers up to the current shortest?

        • (Score: 1) by KritonK on Friday February 21 2014, @08:40AM

          by KritonK (465) on Friday February 21 2014, @08:40AM (#4168)

          If you are asking how they know that rulers with length up to 26 are optimal, yes, they tried every possible permutation!

          If you are asking how they know that the optimal ruler with length 27 is shorter than they shortest currently known, without having performed the brute force calculation, well, they don't. It's just a sense that they have. Those who understand the math might be able to explain why there is a high probability that the heuristically found ruler is not optimal. As for me, I'll stick to my pessimism.

  • (Score: 2, Insightful) by FatPhil on Thursday February 20 2014, @10:30PM

    by FatPhil (863) <pc-soylentNO@SPAMasdf.fi> on Thursday February 20 2014, @10:30PM (#3805) Homepage

    However, you don't need an optimal one for that.

    Similarly, the travelling salesman doesn't *have* to take the shortest route. It just has to be good enough.

    --
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