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Old 2011-09-16, 20:08   #1
ZFR
 
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Default Type of work to get?

I look for prime numbers on my main PC. But I got this second laptop which I use only for travelling. Which means at times it is used a lot, but at other times it can be switched off for several months. Which is why I don't want to use it to find prime numbers.

What kind of work would be most suitable for such a machine? Trial factoring, p-1 factoring (what's the difference between the two)? Double checking?

Thanks,
ZFR
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Old 2011-09-16, 21:05   #2
Christenson
 
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Let me rephrase your question, see if I have it right:
You want your laptop to get shorter assignments, so it can complete useful assignments in the short intervals you have it on, and not to have too much impact when you turn it off for a few months.

CPUs are rapidly becoming very ineffective at TF, so I wouldn't bother. (GPUs are busy cleaning their clocks, outperforming them 10 to 100 to 1 at this job). TF(Trial Factoring) is a brute-force exhaustive search for factors.
P-1 factoring assignments, on the other hand, take a few days apiece, and can use lots of memory (need at least 300M), and can't be done on GPUs, not yet. It's a much more elegant algorithm than TF, but it places certain requirements on the form of the factors it can find, but those factors can be larger than those that can be found by TF.
ECM, especially with small amounts of memory, can also complete in a few days, but generally looks at smaller, known-composite Mersenne numbers.

Double-checking is useful, but will generally take between 2 weeks and a month to complete current assignments. This might be too big a chunk for you. You will want to use the "quit Gimps" option and let it finish the assignment before storing the machine if you want the results to be effective.

I encourage you to visit http://www.mersenne.org/various/math.php and read up on the algorithms proper.
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Old 2011-09-16, 21:49   #3
ZFR
 
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Quote:
Originally Posted by Christenson View Post
Let me rephrase your question, see if I have it right:
You want your laptop to get shorter assignments, so it can complete useful assignments in the short intervals you have it on, and not to have too much impact when you turn it off for a few months.
Yes. That's precisely what I meant. Something that can be completed within 2 weeks or so...

Just a question then. Will p-1 factoring slow down my machine (assuming I leave the default priority)?

If no, then I'll do p-1 factoring. Otherwise I'll do double checking for the time being. It's going to be frequently on till end of November or so, after which I'll what's the best course of action.

Last fiddled with by ZFR on 2011-09-16 at 21:50
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Old 2011-09-16, 22:42   #4
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Quote:
Originally Posted by ZFR View Post
Yes. That's precisely what I meant. Something that can be completed within 2 weeks or so...
What can be completed in that time depends upon how much of that two weeks your laptop is switched on.

Quote:
Just a question then. Will p-1 factoring slow down my machine (assuming I leave the default priority)?
It could, potentially, result in more swapping activity if you have other memory-hungry applications running. This will only be an issue during stage 2 of the algorithm.

You should also be aware that any GIMPS work will "slow down" your machine by flattening its battery more quickly if you are not running on mains.

Quote:
If no, then I'll do p-1 factoring. Otherwise I'll do double checking for the time being. It's going to be frequently on till end of November or so, after which I'll what's the best course of action.
Instead of aiming to finish all your assignments prior to mothballing your machine, if you know it will be restarted eventually, why not just keep on manually renewing your assignments every few weeks during the months it is switched off?
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Old 2011-09-16, 22:47   #5
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Quote:
Originally Posted by Mr. P-1 View Post
Instead of aiming to finish all your assignments prior to mothballing your machine, if you know it will be restarted eventually, why not just keep on manually renewing your assignments every few weeks during the months it is switched off?
or if it doesn't take too long to complete with restarting etc. just set prime 95 to start at login no ?
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Old 2011-09-16, 22:49   #6
R.D. Silverman
 
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Quote:
Originally Posted by ZFR View Post
I look for prime numbers on my main PC. But I got this second laptop which I use only for travelling. Which means at times it is used a lot, but at other times it can be switched off for several months. Which is why I don't want to use it to find prime numbers.

What kind of work would be most suitable for such a machine? Trial factoring, p-1 factoring (what's the difference between the two)? Double checking?

Thanks,
ZFR
Switch to helping out NFS@Home. Now, you can start/stop at will.
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Old 2011-09-17, 01:21   #7
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Quote:
Originally Posted by R.D. Silverman View Post
Switch to helping out NFS@Home. Now, you can start/stop at will.
I almost mentioned that, too....although you will have far smaller bits of the puzzle, they may actually be more useful.
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Old 2011-09-17, 08:43   #8
ZFR
 
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Thanks everyone for their suggestions. It will be on regularly for the next 2 months, so I'll continue with GIMPS for the time being, but as soon as its work becomes much less regular I'll probably switch to NFS@Home.
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