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17744Re: [PrimeNumbers] Re: symmetrical primes

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  • Phil Carmody
    Mar 12, 2006
      --- Alan McFarlane <alan.mcfarlane@...> wrote:
      > Hmm, I noticed that...
      >
      > I have, however, successfully completed an exhaustive search up to 10^12
      > and not found any occurences of 20 primes in symetrical sequence.

      Confirmed. (2^40, rather than 10^12)

      Quoth a 2GHz Athlon (sharing with a nice PIES process):

      bash-3.1$ time ./symprimeven

      real 101m15.817s
      user 84m27.830s
      sys 0m2.550s

      > I'll keep it running for a while, but I may have to resort to running it
      > on my farm for a week or so :)

      I think it is worth trying to find such a cluster, and also that it's not worth
      competing, and definitely worth cooperating. So you have dibbs on the task (if
      you have a farm, that only makes sense -- I only have a herb garden!). If my
      code's faster than yours, you can have it freely. However, as I hinted, my
      code's not very clever.

      I was thinking of a branchless FSM-like approach optimisation, but decided to
      not bother in the end. However, if you want to try to work on optimising the
      task, I can join you in a brainstorm.

      Phil

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