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Old 2008-10-16, 12:52   #1
MrOzzy's Avatar
Apr 2008
Antwerp, Belgium

3·19 Posts
Default 100M exponent idea

We all know with the current technology and software it will take sevral years to test an 100M candidate.
Since it takes so long for someone to complete the test chances someone gives up someware down the line are rather high.
People also will use mutiple cores and waste a lot of cpu time to the overhead trying to finish the LL test as fast as they can. It is a lot more efficient testing multiple candidates at once. So why doesnt GIMPS split up the work? For example someone runs a LL test on an exponent for 1 month. The results of this test are checked in and uploaded to the GIMPS servers. Now the person checking the exponent can continue testing it or pick something else.
If eventually a prime is found everyone working on a specific exponent will be credited according to the amount of work they contributed.
I'm not sure this is technically possible, but if one single computer can continue where it left off another computer also can.
It also will allow double checking someone else work before a complete exponent is finished.
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Old 2008-10-16, 12:59   #2
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"Tim Sorbera"
Aug 2006
San Antonio, TX USA

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Technically this is possible, but would require transferring files that are several megabytes, so probably won't be done.
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Old 2008-10-16, 15:27   #3
jrk's Avatar
May 2008

44716 Posts

Yeah the smallest 100M digit Mersennes would take about 40 MB of storage and bandwidth to store an interim file.

Last fiddled with by jrk on 2008-10-16 at 15:27
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Old 2008-10-16, 19:03   #4
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Sep 2007
Liverpool (GMT/BST)

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40mb would take me about 20min to upload i think currently although in the future i could see a plan like this working
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Old 2008-10-16, 23:18   #5
potonono's Avatar
Jun 2005

19310 Posts

Is that theoretical 40 Mb compress, or uncompressed?
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Old 2008-10-16, 23:25   #6
axn's Avatar
Jun 2003

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Originally Posted by potonono View Post
Is that theoretical 40 Mb compress, or uncompressed?
Theoretically, the intermediate values of the LL test should be fairly random and thus compress poorly (less than 5% reduction).

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Old 2008-10-16, 23:43   #7
retina's Avatar
"The unspeakable one"
Jun 2006
My evil lair

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I cant see how this "idea" would encourage people to run 100M numbers in any way. Someone runs, say, the first million iterations then uploads the residue file to somewhere, then another person downloads it and runs another million, etc. How does that help towards running it any faster? How does that stop people being bored with it? There are still no final results for many years and people just see numbers (and large data files) coming and going for years with seemingly no conclusion. What happens when a final test is returned with a bad residue? After all the hard work everyone does and one bad CPU/MOBO has ruined the result for all! Who provides the huge bandwidth and disc space to store the interim files? That is not going to be cheap.
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Old 2008-10-16, 23:46   #8
joblack's Avatar
Oct 2008

3·5·72 Posts

There would be also the problem whom to give the 75.000 USD (from the EFF price).

Does prime95 support the nehalem 12 (/24) Core architecture. It should be possible to shorten the time for one 100m digital number under 1 year?!
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Old 2008-10-17, 00:00   #9
jrk's Avatar
May 2008

3·5·73 Posts

Originally Posted by potonono View Post
Is that theoretical 40 Mb compress, or uncompressed?
The big numbers in the interim files are not compressible at all (well, it could theoretically be compressed very small, if your compression algorithm includes a Lucas-Lehmer function to decompress it but that would be defeating the purpose of storing the interim file in the first place...).

Just for fun I compressed some interim files with gzip and bzip2.

Gzip inflates the files by 0.016%.

Bzip2 inflates the files by 0.44% and takes 6 times as long as gzip to do so.

Last fiddled with by jrk on 2008-10-17 at 00:04
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Old 2008-10-17, 00:11   #10
ATH's Avatar
Dec 2003

338610 Posts

Savefile for my 46M exponent (13.87M digits) takes 5.76Mb, so that is around 41.5% of the digits in bytes, so if this holds a 100M digit exponent would take 41.5Mb.

Last fiddled with by ATH on 2008-10-17 at 00:11
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Old 2008-10-17, 00:47   #11
Batalov's Avatar
Mar 2008

994210 Posts

Dudes, the save file simply contains a 64-byte header with the status data and then the (rotated) residue modulo your number (that is p bits). That means that the size of the savefile is 64+p/8 bytes (=40551Kb for the lowest number), and it is surely incompressible (because it is essentially random noise).
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