20110628, 06:53  #1 
4864_{10} Posts 
Dual Core to process single work unit?
I have a Core 2 Duo MacBook. In the past I have been automatically given 2 work units assignment by GIMPS being worked on by Worker1 and Worker2.
I have changed my preference to work on the LL100M+ and was given one work unit. Accordingly, I changed my worker configuration as follows: Worker#1  Whatever makes the most sense  Smart assignment Worker#2  100,000,000 digit numbers to test  Smart assignment My questions: 1) Is it possible to make both workers process a single work unit and not two separate Mersenne number candidates? 2) If so, what settings do I change? 3) Just a thought: Would changing Worker#1 setting to "100,000,000 digit numbers to test" do the trick? Or will it be automatically assigned another number to test? I'd prefer testing only one because I don't want my computer to be overwhelmed. Thanks for any help 
20110628, 15:33  #2  
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
5·953 Posts 
Quote:
1) Yes 2) I can only speak for the WINDOWS GUI ... not sure if MAC menus are different:  Test ... Stop (All workers)  Test ... Worker Windows  Number of workers to run: 1  Worker Number: All workers OR Worker #1  Type of work to get: 100,000,000 Digit numbers to test  CPU Affinity: Smart Assignment  CPUs to use: 2  OK  Test ... Start 3) If all you do is change the work type that worker will continue to completion whatever is currently assigned and then start the new work type. If Worker #2 already has a 100,000,000 in progress and you want to move it to Worker #1  Test ... Stop (All workers)  Test ... Exit  Find and edit your worktodo.txt file (or whatever MAC names it)  physically cut and paste the appropriate lines from below Worker #2 to below Worker #1  Save it  Execute Prime95 You say you "...don't want my computer to be overwhelmed..." Whether you have each core processing their own test or both cores on one your PC's CPU will be virtually 100% busy all the time and without good cooling and ventilation could get quite hot. The vast majority of us run all our PCs 100% all the time and rarely have any issues. There is a bigger risk if your PC's vents get clogged with dust OR if you OverClock a lot. If you are concerned about overwhelming your PC you can set up to have 1 worker window with 1 CPU realizing that your PC will then be 50% utilized by Prime95 and all tests will take twice as long of you will complete half as many. If you want to abandon whatever Worker #1 is currently working on so it can immediately continue the 100,000,000 test. Find the exponent of that assignment  Test ... Status  Note the exponent number only (not the preceeding M)  Advanced ... Unreserve Exponent OR do it via the Server noting that your PC won't actually stop that assignment until the next scheduled check in date/time OR until you:  Advanced ... Manual Communication  Send new end dates 

20110630, 01:39  #3 
"James Heinrich"
May 2004
exNorthern Ontario
2·17·103 Posts 
Adding more specific numbers: A 100Mdigit test is roughly 5000GHzdays of work. A moderately fast Core2 Duo notebook CPU (e.g. P8700) will complete around 3GHzdays/day of work. Assuming it does nothing else (but it presumably will), runs 24/7, doesn't overheat (quite likely with a notebook), and you get 100% efficiency spreading across both cores (you won't), it should take around 2.3 years to complete a single test. Remembering that's a bestcase scenario (and 4+ years is realistic on that hardware) you'd probably be better off sticking with "whatever makes sense", which will likely be "normal" LL tests. Doublechecking LL worktype would also be a good choice.

20110703, 07:50  #4 
"Lucan"
Dec 2006
England
2·3·13·83 Posts 
More cold water...
A 100M digit test is ~ 10x less likely to find a prime that a 10M digit one.

20110703, 10:51  #5 
"James Heinrich"
May 2004
exNorthern Ontario
2×17×103 Posts 
I have to disagree with you there. Working in that range is less likely to find a prime due to longer work times, therefore fewer exponents processed, therefore lower cumulative chance of finding a prime; but wouldn't each exponent have a similar (very low) individual chance of being prime?

20110703, 13:02  #6  
Dec 2010
Monticello
5×359 Posts 
Quote:
First, if you do a 100M digit test, it will take much (36x) longer than the current M(50M) LL tests, and that has a significant opportunity cost in fewer factors that can be checked. (That is, if the OP even has enough patience and persistence to complete the one test, no surprise or blame intended if not, you are an absolute saint if you do  that probability is much less than unity) Second, I don't think anyone expects Mersenne Primes to get any more common as the exponents get bigger. I would expect them to get less common, on the basis that the probability for a "random" number of the larger size to be prime decreases. But I don't think this is by a factor of 5 or 10, or even 2  I'd have to go look up the formula for the number of primes below a given point, and I think we'll get something like 22/26 or so. 

20110703, 13:42  #7  
Jun 2003
1010000011001_{2} Posts 
Quote:
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20110703, 13:58  #8 
Dec 2010
Monticello
5·359 Posts 
Indeed I have taken one log too many...LLDs deal with 10M digit #s, LLs deal with 20M digit #s, and a 100M digit test deals with a 100M digit #.

20110704, 03:19  #9  
"Lucan"
Dec 2006
England
2×3×13×83 Posts 
Quote:
I caught WBLipp out with this last year. I asserted that a 100M digit test was 10x less likely to find a prime than a 10M one. "No. The probability goes as 1/logN. It's called the "Prime Number Theorem". I just grinned. Confusing as the terminology is, the "exponent" is log_{2} (the Mersenne number). # digits is log_{10} (the Mersenne number) Last fiddled with by davieddy on 20110704 at 03:41 

20110704, 03:58  #10  
"Lucan"
Dec 2006
England
2·3·13·83 Posts 
Quote:
between 33M and 50M, and one with exponent between 330M and 500M. It is the density of prime exponents which doesn't differ much (exercise*) so we expect to have to do nearly 10x as many LL tests. David * I reckon 7/8 th Last fiddled with by davieddy on 20110704 at 04:45 

20110730, 12:53  #11  
Oct 2008
n00bville
1011011000_{2} Posts 
Quote:


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