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Re: SoB finds 10th prime!

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  • Jean Penné
    Many congrats to the discoverer and all participants for this outstanding result!! However, I have two questions about it : 1) If I am not wrong, the record
    Message 1 of 8 , May 5, 2007
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      Many congrats to the discoverer and all participants for this
      outstanding result!!

      However, I have two questions about it :

      1) If I am not wrong, the record has been posted to SoB on March 26 ;
      why is it not yet posted to the top 5000 database ?

      2) What is/are the proving program(s)?

      Woul you excuse my curiosity...

      Jean
    • Phil Carmody
      ... That s quite optmistic. Maybe the one just found was that one! ... Remind me to never ignorantly cross you, Jack ;-) ... We re most of the way there.
      Message 2 of 8 , May 6, 2007
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        --- Jack Brennen <jb@...> wrote:
        > Phil Carmody wrote:
        > > Jack, or someone, any model for when the next one's due,
        > > assuming a sperical homogeneous Poisson?
        >
        > I can't seem to find any "real" numbers on how far the remaining 7
        > k values have been tested. The SoB pages seem to indicate that all
        > of them have been tested to n=10^7, but that can't be an accurate
        > accounting.
        >
        > However, if we assume that n=10^7 is accurate for each of them,
        > there would be about a 50% chance of finding a prime for one of
        > the 7 candidate k values with n < 14675000.
        >
        > That's the good news.

        That's quite optmistic. Maybe the one just found was that one!

        > The bad news is that in order to have a 50% chance of resolving
        > the Sierpinski conjecture, you'd need to search for all
        > n < 2965000000000. (2.965*10^12)
        >
        > That's an improvement over the last numbers I remember putting
        > together, which would have given somewhere around a 40% chance of
        > resolving the Sierpinski conjecture by that limit...
        >
        > http://tech.groups.yahoo.com/group/primenumbers/message/10258

        Remind me to never ignorantly cross you, Jack ;-)

        > Still, even a single test in the n > 10^12 range is beyond our
        > reasonable capabilities today -- we're just not ready to do
        > modular arithmetic on terabit numbers.

        We're most of the way there. Compared with those flipping iron rings at least.
        Doing it 10^12 times I think will be a harder target.

        > Also, the chance to resolve the conjecture before n = 10^9 has
        > risen to 3.98% from the previous 2.45%.

        Impressive.

        > I think a lot of this improvement in the outlook (modest as it
        > is) is due to the fact that this latest k value (19249) was
        > one of the three "toughest" k values to crack of the original
        > seventeen (one of the three lowest Proth weights). Only the
        > k values of 22699 and 67607 (both still uncracked) have lower
        > Proth weights.

        Ah probably the single most pervasive snippet of utter wrongness
        I've seen various people throw around on their project fora is
        that getting rid of the dense ones is best. Of course, that's
        the worse possible situation, you want to get rid of the most
        difficult numbers sooner rather than later. I've tried telling
        them that, but most just didn't seem to grok the concept.

        Thanks for the quick numerics, as always, Jack.

        Phil

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      • Jack Brennen
        ... First, I realize reading this that I m being way too precise. With the unknown depth of search, and the inaccuracy of the Proth weight values, I should
        Message 3 of 8 , May 6, 2007
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          Phil Carmody wrote:
          >>
          >> However, if we assume that n=10^7 is accurate for each of them,
          >> there would be about a 50% chance of finding a prime for one of
          >> the 7 candidate k values with n < 14675000.
          >>
          >> That's the good news.
          >
          > That's quite optmistic. Maybe the one just found was that one!

          First, I realize reading this that I'm being way too precise. With
          the unknown depth of search, and the inaccuracy of the Proth weight
          values, I should probably have just said n < 15_000_000.

          In any case, with the remaining 7 k values, if they've been
          completely searched up to n < A, we're about 50% to find another
          prime with n < 1.5*A. A very quick justification which is very
          close to being mathematically "correct":

          The remaining 7 k values should produce an aggregate total of about
          1.25 primes per "octave" (A < n < 2*A), and the distribution should
          be very Poisson-like.

          To get a 50% chance of a hit in a Poisson distribution, we need an
          expectation of log(2) primes. That requires 0.55 octaves, or
          A < n < 1.47*A.

          >
          > Remind me to never ignorantly cross you, Jack ;-)

          If you read the forum link where Louie originally trashed my math,
          he admitted very quickly afterward that he did make a mistake and
          that I was probably "in the ballpark"...

          >
          >> Still, even a single test in the n > 10^12 range is beyond our
          >> reasonable capabilities today -- we're just not ready to do
          >> modular arithmetic on terabit numbers.
          >
          > We're most of the way there. Compared with those flipping iron rings at least.
          > Doing it 10^12 times I think will be a harder target.

          Keeping even a single terabit number in high-speed RAM is far out of
          the capability of the vast majority of computers in existence -- that's
          my point. Clearly we have the capability to build such hardware, but
          the whole point of SoB and other cooperative computing projects is to
          use inexpensive commonly available PC-like devices, and they're still
          many years away from being able to hold even a single terabit number
          in RAM.

          >
          > Ah probably the single most pervasive snippet of utter wrongness
          > I've seen various people throw around on their project fora is
          > that getting rid of the dense ones is best. Of course, that's
          > the worse possible situation, you want to get rid of the most
          > difficult numbers sooner rather than later. I've tried telling
          > them that, but most just didn't seem to grok the concept.
          >

          To put things in perspective, the toughest two k values have an
          aggregate expectation of 0.15 primes per octave. In very rough
          numbers, that means an expectation to find 1 prime between these
          two k values as we push n from 10^7 to 10^9 (about 6.6 octaves).
          And note of course that 1 prime between those two k values won't
          resolve the conjecture.
        • Jean Penné
          Now I see the responses to my two questions! Hurrah for Seveteen or Bust!! Jean
          Message 4 of 8 , May 8, 2007
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            Now I see the responses to my two questions!

            Hurrah for Seveteen or Bust!!

            Jean

            --- In primenumbers@yahoogroups.com, Jean Penné <jpenne@...> wrote:
            >
            > Many congrats to the discoverer and all participants for this
            > outstanding result!!
            >
            > However, I have two questions about it :
            >
            > 1) If I am not wrong, the record has been posted to SoB on March 26 ;
            > why is it not yet posted to the top 5000 database ?
            >
            > 2) What is/are the proving program(s)?
            >
            > Woul you excuse my curiosity...
            >
            > Jean
            >
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