20081016, 12:52  #1 
Apr 2008
Antwerp, Belgium
3·19 Posts 
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. 
20081016, 12:59  #2 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
2×3×23×31 Posts 
Technically this is possible, but would require transferring files that are several megabytes, so probably won't be done.

20081016, 15:27  #3 
May 2008
447_{16} 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 20081016 at 15:27 
20081016, 19:03  #4 
Just call me Henry
"David"
Sep 2007
Liverpool (GMT/BST)
2·2,999 Posts 
40mb would take me about 20min to upload i think currently although in the future i could see a plan like this working

20081016, 23:18  #5 
Jun 2005
USA, IL
193_{10} Posts 
Is that theoretical 40 Mb compress, or uncompressed?

20081016, 23:25  #6 
Jun 2003
5×23×47 Posts 

20081016, 23:43  #7 
Undefined
"The unspeakable one"
Jun 2006
My evil lair
2^{2}×13×127 Posts 
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.

20081016, 23:46  #8 
Oct 2008
n00bville
3·5·7^{2} 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?! 
20081017, 00:00  #9 
May 2008
3·5·73 Posts 
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 LucasLehmer 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 20081017 at 00:04 
20081017, 00:11  #10 
Einyen
Dec 2003
Denmark
3386_{10} 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 20081017 at 00:11 
20081017, 00:47  #11 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
9942_{10} Posts 
Dudes, the save file simply contains a 64byte 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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