-----Oprindelig meddelelse-----
From: Brian J. Beesley
Sendt: lø 23-11-2002 13:23
>This is not a particularly effective cheat; you still end up having to
do
>significantly more than half of the computational work. Is there any
evidence
>that this may be happening?
No, and I am not the GIMPS police. It would offcourse be quite
easy simply to check all accounts having done 5+ years TF and having
more than 0,6 years pr. foundfactor. On the other hand some accounts
could be very old and back in those days a factor could have been found
in less effort than now a days appr. 0,5 y/ff. NetForce and Challenge
seems to be good candidates for accounts with a very low effort pr. ff.
>Does it make sense to impose a "penalty clause" i.e. if someone
subsequently
>finds a factor in a range you claim to have sieved, you lose 10
times the
>credit you got for the assignment? N.B. There will be
_occasional_ instances
>where an "honest" user misses a factor, possibly due to a
program bug,
>possibly due to a hardware glitch.
I'd rather not like the "penalty"/ punishment. A reward equal to
the full effort of doing the TF would be much better - and under those
circumstances no one would try to cheat because a factor found at eg. 63
bits would reward very well.
>> The exponents above
>> 79.300.000 are still candidates, though George has chosen to
limit his
>> program to this size and I think with very good reason.
>Hmm. As it happens, one of my systems has just completed a
double-check on
>exponent 67108763. This took just over a year on an Athlon
XP1700 (well,
>actually it was started on a T'bird 1200). The fastest P4
system available
>today could have completed the run in ~3 months. The point is
that running LL
>tests on exponents up to ~80 million is easily within the range
of current
>hardware.
Yes, but that kind of hardware was not at the market in 1995.
But regarding Moores law George should have predicted the P4 and SSE2?
>Personally I feel it is not sensible to expend much effort on
extremely large
>exponents whilst there is so much work remaining to do on
smaller ones. I
>justify running the DC on 67108763 as part of the QA effort.
Sure. Let's get a new prime and let us have it fast.
>> BTW, the list of found factors contains 2.500.000+ but the
"top
>> producers list" only contains 30.000- of these. GIMPS must be
>> responsible for far more than only 30.000 factors. Any
explanation for
>> that?
>Well, there are a lot of factors which can be found by
algebraic methods
>rather than by direct computation: e.g. if p+1 is evenly
divisible by 4, and
>p and 2p+1 are both prime, then 2^p-1 is divisible by 2p+1.
Evenly? What about 11, 83, 131 and 251 giving: 3,21,33 and 63.
Are these just plain luck or does it exist one p+1 / 4 is not even and
the factor 2p+1 does not fit?
Have a nice day
tsc
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