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Re: Time for finding a prime number in practice

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  • Dario Alpern
    ... multiplies. Even ... take. The variation ... prime to 1000 ... digits - using ... was aware that ... as to how long the ... hint as to when the ... the
    Message 1 of 8 , Jul 24, 2006
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      --- In primenumbers@yahoogroups.com, "julienbenney" <jpbenney@...>
      > Re: "A PRP test of a 2M digit number consists of several million
      multiplies. Even
      > testing 100 multiplies is sufficient to work out how long 2M will
      take. The variation
      > between runs is normally minimal."
      > I have had this problem: I have been trying to find the previous
      prime to 1000
      > factorial - which as you would probably know is a number of 2568
      digits - using
      > Dario Alpern's site "http://www.alpertron.com.ar/ECM.HTM". Whilst I
      was aware that
      > site would take some time to find the number, it gave so few clues
      as to how long the
      > number would take to find that after about forty minutes with no
      hint as to when the
      > number would be found I just stopped and gave up.
      > Whilst I am well aware that there is much better software for doing
      the job, I wonder
      > if any of you have done that or a very closely related experiment
      and what you
      > findings are?!

      The expression evaluator I programmed for the applet is not very
      smart and it computes SPRPs for all odd numbers before or after the
      argument. If sieving is added to the process, it could be about 10
      times faster.

      Best regards,

      Dario Alpern
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