Thread: Sieve Vs PRP
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Old 2007-03-23, 17:30   #2
hhh's Avatar
Jun 2005

373 Posts

Sieve vs PRP, one of my favorite topics!

Let me put it like this: Joe Averagefactor eliminates a candidate at about 25M. Such an LLR test takes like forever; at least several weeks.
So, as long as we are not waiting for a factor several weeks, we should sieve.

HA!, you say, but if I do a little LLR-test now, no harm is done. Let us LLR up to 5M and sieve then. Ok, I reply, but then you wouldn't have got all these factors for 3M-5M which would have saved considerable LLR-work.

HA! you say again, but I would have found a prime. And hence we could sieve faster. Ok, I say again, but not much. Sieve speed is logarithmic, and adding or removing 5% of the candidates results in 2-3% speed change only. And even if we sieve first, and half of the factors go out of the window and never save an LLR-test, well, then we should not sieve until we get a factor every 4 weeks, but every 2 weeks. And that's still far ahead.

In this manner, I'm not very sorry if we LLR less and sieve more. But I would be even more happy if we could maintain the LLR-rate and sieve more.

But then again I think that all this is random fluctuation, and that we have to be happy with what we get.

Bottomline: LLR is cool, sieve is cooler.

Yours H.

PS: My exhaustive description of my point of view isn't meant to prevent others to express their points of view. Especially opinions about how to raise interest (without going BOINC) would be interesting, I think. H.
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