PrimeGridʼs
Generalized Fermat Prime Search	  On 29 Oct 2011 11:31:47, PrimeGrid’s PRPNet found the largest known
Generalized Fermat mega prime:
361658262144+1
The prime is 1,457,075 digits long and enters Chris Caldwell's “The Largest
Known Primes Database” (http://primes.utm.edu/primes) ranked 1st for
Generalized Fermat primes and 24th overall.
The discovery was made by Michel Johnson of Germany using an NVIDIA
GeForce GTX 550 Ti in an AMD PHENOM II X6 1100T @ 3.3GHz system with
4GB RAM, running 32 bit Windows XP. This GPU took about 1 hour and 45minutes to probable prime (PRP) test with GenefCUDA. (NOTE: This is the firstprime found by GeneferCUDA!) Michel is a member of the SETI.Germany team.
The prime was verified on 5 Nov 2011, by an Intel Xeon 5410 @ 2.33GHz with
16GB RAM, running Windows Server 2003 x64. This computer took a little over
50 hours 40 minutes to complete the primality test using pfgw64.
The credits for the discovery are as follows:
1. Michel Johnson (Germany), discoverer
2. PrimeGrid, et al.
3. AthGFNSieve, sieve program developed by David Underbakke
4. GeneferCUDA, probable prime program developed by Shoichiro Yamada
5. PFGW, primality program developed by Chris Nash & Jim Fougeron withmaintenance and improvements by Mark Rodenkirch
Entry in “The Largest Know Primes Database” can be found here:
http://primes.utm.edu/primes/page.php?id=102720
This is only the 4th known GFN prime at N=262144. Using a single PC would
have taken years to find this prime. So this timely discovery would not have beenpossible without the hundreds of volunteers who contributed their spare CPUcycles. A special thanks to everyone who offered their advice and/or computing
power to the search - especially David Underbakke, Mark Rodenkirch and Geoff
Reynolds who were major forces in moving the project forward. Also, thank you
to all the sievers, especially Honza Cholt, and PRPNet’ers who contributed to thiseffort.
This is PrimeGrid’s 17th mega prime. The Generalized Fermat Prime Search willcontinue to seek even larger primes. To join the search please visit PrimeGrid:
http://www.primegrid.com

	  About PrimeGrid

PrimeGridʼsGeneralized Fermat Prime SearchPrimeGrid is a distributed computing project, developed by Rytis Slatkevičius,Lennart Vogel, and John Blazek, which utilizes BOINC and PRPNet to search forprimes. PrimeGrid's primary goal is to bring the excitement of prime finding to the"everyday" computer user. Simply download the software and let your computer
do the rest. Participants can choose from a variety of prime forms to search. Witha little patience, you may find a large or even record breaking prime.
BOINC
The Berkeley Open Infrastructure for Network Computing (BOINC) is asoftware platform for distributed computing using volunteered computerresources. It allows users to participate in multiple distributed computing
projects through a single program. Currently BOINC is being developed bya team based at the University of California, Berkeley led by DavidAnderson.
This platform currently supports projects from biology to math to astronomy.
For more information, please visit BOINC: http://boinc.berkeley.edu
PRPNet
PRPNet is a client/server application written by Mark Rodenkirch that is
specifically designed to help find prime numbers of various forms. It is easily
ported between various OS/hardware combinations. PRPNet does not run
each PRP test itself, but relies on helper programs, such as LLR, PFGW,phrot, and genefer to do the work.
For more information, please visit PrimeGrid’s PRPNet forum thread:
http://www.primegrid.com/forum_thread.php?id=1215
For more information about PrimeGrid and a complete list of available prime
search projects, please visit: http://www.primegrid.com