Project News - PrimeGrid

[BF]

From the PrimeGrid news feed:

Record AP25 Found

Thursday, 3 September 2009 12:40 AM

PrimeGrid has found a record AP25 (Arithmetic Progression of 25 primes). This is PrimeGrid’s second AP25 and only the third known.  It has an ending term of 37814740008933889 surpassing the old record of 15523154536267043. The finder is Jochen Beck (dh1saj) of Germany.  He is a member of team SETI.Germany. The progression is written as 20919497549238289+3155495*23#*n for n=0..24.  It was found in the AP26 Search. For more details on this find and the AP26 search, please see this forum post.

[BF]

From the PrimeGrid news feed:

Megadigit Probable Prime Found

Thursday, 3 September 2009 10:00 AM

Congratulations to Ben Maloney (paleseptember) who discovered the megadigit probable prime 2^4583176+2131. At 1,379,674 decimal digits, this is the first known probable prime with over a million digits.  It should soon appear as the new probable prime record at the website of Henri and Renaud Lifchitz, PRP Records: Probable Primes Top 10000.
Ben is participating in the project "Five or Bust" - The Dual Sierpinski Problem.  This project is outside of PrimeGrid and can be located in the Mersenne forum.  For additional information about this project, please see the Welcome to "Five or Bust!" thread.  There are only 2 remaining sequences.  To help with PRP testing, see this thread.  To help with sieving, see this thread.

[Hurricane]

PrimeGrid's 2010 Challenge Series. The Winter Solstice Challenge Start's... now!

http://www.primegrid.com/ 

[Dataman]

Congradulation's Brett!!! 

2011-01-18: PrimeGrid - Mega Prime found for The Riesel Problem
On 14 Jan 2011 9:03:07 UTC, PrimeGrid?s The Riesel Problem project eliminated k=428639 by finding the Mega prime: 428639*2^3506452-1

The prime is 1,055,553 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 29th overall. This is the 2nd largest prime found in The Riesel Problem and PrimeGrid's second elimination in 2 months. 62 k's now remain.

The discovery was made by Brett Melvold of Australia using an Intel i7 920 @ 2.67GHz with 6GB RAM, running Windows 7. This computer took 11 hours and 13 minutes to complete the primality test using LLR. Brett is a member of the BOINC@AUSTRALIA team.  

[veebee]

Brett is a member of the BOINC@AUSTRALIA team.  

hmmm ... got me TWO of those machines.... makes me want to swap over to Primegrid ! 

actually - I shall go and do the 'build/ upgrade story' I want to do for the "Newcomers" section here... for those who may want to do some work of their own (save BUCKS) but may also think it is a bit beyond them ---- well, it aint !

[kashi]

Upgraded to Catalyst 11.6 recently, Sean?

The OpenCL drivers included with Catalyst 11.6 may be incompatible with Proth Prime Search (Sieve) v1.38 (ati13ati) tasks on HD 4xxx series cards.

You could try an earlier Catalyst version. Someone recommended 11.5 or 11.3 but not 11.2 or 11.4 for some reason.

Try installing Cat 11.5 or 11.3 first. If it still doesn't work and gives the same "Error: Building Program (clBuildProgram): Program build failure calclCompile failedError: Creating kernel start_ns failed!" you may need to run DriverSweeper or something similar to remove the OpenCL component of Catalyst 11.6 before installing Cat 11.5 or 11.3.

[kashi]

It's not certain that an older driver will fix it, it is only a possibility that I gleaned from reading the PrimeGrid forums.

Yes it's very deceptive on PrimeGrid ATI currently. When you look at the details of the work units of your errored tasks, you often see many other tasks sent to wingmen that have also errored. This would lead you to believe that there is something wrong with the work units themselves because the iterations (tasks) appear to be erroring for almost everyone. However if you look closer at the errors you will see a pattern of HD 4xxx cards with Catalyst 11.6, a few HD 38XX incompatible with OpenCL, HD 57xx with something also incompatible, either Catalyst 11.6 or possibly an older driver with no APP section (OpenCL) and a lesser number of HD 58xx with errors.

But when you look at the details of work units of an ATI card that is successfully completing tasks, you will often see the same thing. Many errors in the tasks sent to wingmen. It's because there's a number of people with misconfigured/incompatible ATI cards on PrimeGrid currently and if the number of tasks sent to these cards is not properly limited they become "runaways" and produce thousands of errored tasks very quickly. So even a relatively small number of runaway ATI cards can give the impression of almost everyone having errors.

[kashi]

Excellent, well done.