20180111, 04:14  #1 
Jan 2018
2 Posts 
What do the different types of work each mean?
I am a math teacher and am pretty computer savvy, but not sure the exact definition of the types of work. I would love to find the next prime number or the biggest one, but what jobs would that be? :) Thanks

20180111, 14:40  #2 
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
2A32_{16} Posts 
Well, if you want to find the next 'biggest known prime', you should set your system for "World record sized numbers to test". This will get from the server exponents that are larger than the most recent largest known. (Practically of late, this has also meant the same as "First time tests", but not at the moment.)
If you want to just look for any prime (size being irrelevant), choose "First time tests". If you want faster testing, but with a lower chance of finding a prime choose "Doublecheck tests". These are numbers that have been tested already, but need a run on a different machine to check that there were no errors in the original test. These are smaller numbers and thus run faster. If you want to go for the big boy, choose "100,000,000 digit numbers to test". This is the next prime size that will win the EFF award. It will be both world record size and a first time test. It will also take longer to test and thus be prone to more problems. I don't recall the time to run with the current best consumer level hardware, but it is over a month per exponent. 
20180112, 02:57  #3  
Dec 2014
3·5·17 Posts 
Here are all the work types from the prime95 source code.
Most people use work type 0. It checks how fast your machine is and picks the best work for it. A newer machine will get some double check (type 101) jobs to test out your hardware, and when it passes then move up to type 100 jobs. All the factoring methods help save work by eliminating exponents from further consideration. ECM is elliptic curve method of factoring. P1 is Pollard's rho method of factoring. PRP stands for probable prime. There is a cash prize for finding a 100 million digit prime and some of the work types are for that. Read the prime95 license agreement, you are agreeing to split any prizes with the GIMPS project leaders. Which is very fair. Quote:


20180112, 23:41  #4 
Oct 2017
++41
5^{3} Posts 
There is an entry in the Mersenne Wiki about the different Worktypes:
http://www.mersennewiki.org/index.php/Worktype One thing that is missing is ECM vs. ECMCF. I assume ECM is for Mersennenumbers which don't have a known factor yet and ECMCF for Mersennenumbers with one known factor but unknown other factors. Thus ECM more likely for bigger Mersennenumbers and ECMCF more likely for smaller Mersennenumbers. Is that correct? 
20181016, 22:33  #5  
Oct 2018
2^{2} Posts 
Quote:
New to GIMPS. It looks like there are more options now in v29 and this is still kind of confusing on how to find the next / biggest Mersenne Prime... So for instance what is the correct "100,000,000 digit numbers to test" PRP or LL? Thanks for any help! Last fiddled with by Uncwilly on 20181017 at 13:56 Reason: Removed offsite link, same as attached image. 

20181017, 14:03  #6  
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
10101000110010_{2} Posts 
Quote:
Selecting "World Record" will always select a test on a number larger than the largest known prime. At the moment "First time" is also in this range. Double checks may never find a new prime. And almost certainly it won't be a world record. ECM is a type of factoring and like all of the factoring methods can't prove a number is prime. Trial factoring can find factors and thus prove that a number is not prime. P1 is another factoring method. Cofactors are what is left after a factor is found. Testing these will never find a new M Prime. Factoring them is for those that want a complete set of factors for a number. (This is part of what is done in GIMPS as well as finding new records.) Last fiddled with by Uncwilly on 20181017 at 14:07 

20181017, 14:46  #7  
Einyen
Dec 2003
Denmark
5×683 Posts 
Quote:
If you are using a Xeon with ECC RAM it does not matter as much, but PRP tests would still be safer. 

20181017, 18:38  #8 
Oct 2018
2^{2} Posts 
Thank you for the informative answers everyone!
Cheers, Jordan 
20181021, 13:10  #9 
Aug 2002
3×5×569 Posts 

20181021, 14:13  #10 
Einyen
Dec 2003
Denmark
110101010111_{2} Posts 
If a positive test is found 2 more LL tests are needed to double check. But not much of a disadvantage, since 4+ different double checks are usually done anyway.

20181021, 14:24  #11 
Random Account
Aug 2009
Not U. + S.A.
2,383 Posts 

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