7th rank under threat

[vaughan]

Just a heads-up that our team's World 7th rank in the BOINC PrimeGrid Project is under threat from Team Picard. They are roughly 100,000 behind us. Bok's stats show they overtake in about 3 days.

[PoorBoy]

:BangHead: ... :cussing:... No rest for the Weary I guess ... :icon_lol: ... I'll try to move some Cores over to the PrimeGrid Project but it may be a few days before I can. I keep a fairly large Cache of Cosmo Wu's & I'm tight to the Deadlines for them so I'll have to run them down some before I can ... :icon_neutral:

[Steve Lux]

Is this Cullen-Woodall prime search method supposed to be superior to the Sieve of Eratosthenes which we learned to find primes in school?

[jmblazek]

Is this Cullen-Woodall prime search method supposed to be superior to the Sieve of Eratosthenes which we learned to find primes in school?
FYI...in today's major prime searches, "generally" you start off with a data set, seive factors out of it until it takes longer to sieve than to primality test, then you primality test.

That's the goal with all of PrimeGrid's prime searches (TPS, Cullen/Woodall, 321, & PSP). Of course, some projects are sieved better than others. The C/W search will continue to sieve as n will continue to increase. Currently, for C/W, primality testing is in the 3.5M<n<4M range and sieving is taking place in the 4M+ range. M=million; n*2^n-1

The gcwsieve program, which PrimeGrid uses, was developed by Geoff Reynolds and has this in the readme.txt file:


This is a sieve for Generalised Cullen and Woodall numbers n*b^n+/-1, where
b is fixed. The algorithm was taken from a mersenneforum.org post by Harsh
Aggarwal. Modular arithmetic and Sieve of Eratosthenes code was taken from
srsieve, much of which was contributed by Mark Rodenkirch.

PrimeGrid offers both sieving and primality testing in project selections under Your Account/PrimeGrid preferences. You can choose which project you want to run. Currently only C/W and PSP offer sieves...the other's are non-BOINC sieves.

If you want to find primes, select the projects that offer LLR...LLR being the primality testing program. Other than TPS, these WU's range from 10 hours to 30 hours. TPS is typcially around 5-20 minutes depending on your CPU. The sieves take around 30-45 minutes depending on your CPU.

If you're only interested in cobblestones, then I'd suggest running the sieves to see which one offers the better credit on your CPU.

Finally, if you have 64 bit Windows and you just want cobblestones, HANDS DOWN the BEST for your machines are the sieves. 64 bit Linux for the sieves will be coming at the first part of 2008. Don't expect a 64 bit version of LLR. Although 32 bit apps will run in 64 bit OS, there's no advantage.

For those who have 32 bit and 64 bit farms and want to maximize credit but still want to find primes, the best thing to do is set up different venues (home, work, school) and assign your 32 bit to one and your 64 bit to another. Then set one venue to sieve and the other to LLR.

I hope this helps.