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Old 2020-09-09, 16:54   #46
storm5510
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Aug 2009
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Quote:
Originally Posted by kriesel View Post
https://www.mersenne.ca/exponent/10516021 shows the factor has k=15. That was found so easily that it was probably found very long ago, and it may predate GIMPS and record keeping of trial factoring levels completed per exponent, or any organized system of assignments / reservations.

Another way the situation may occur, is that old factoring gets removed from the database to manage the database size. See the note about that at the bottom of any https://www.mersenne.org/results/ output:
Code:
*Count does not include any results reported to the old v4  server. Also, to keep the database size down, some TF-LMH result lines  are deleted before 365 days pass. Any factors found, trial factoring  limits, and CPU credits are remembered, but the result lines will not  appear in the table above or appear in the count of total results for  the last 365 days.
(Some people mistakenly believe that the absence of listing a bit level of TF such as in an exponent report means it was skipped, and redo it. Please everyone, don't do that. Duplication of TF already completed is not productive.)

As to why PRP-CF is called a first-time test, it's the first time the cofactor is primality tested. This is the same terminology and similar sequence as for an exponent with no factor found. The usual order when searching for Mersenne primes is TF up to a stopping point, if no factor found yet, run a P-1, if no factor found yet, then a first primality test, then eventually a double check of the primality test, or now a Cert of the proof.

The cofactor being tested for primality in PRP-CF is whatever is left after dividing the Mersenne number by the known factors. See for example https://www.mersenne.org/report_expo...0516361&full=1 (the only PRP-CF I've run.)
Or definition of cofactor, #11 of https://www.mersenneforum.org/showpo...65&postcount=3
PRP of a cofactor does not help find new Mersenne primes. It may aid in further factoring of composite Mersenne numbers, which some people like. See https://www.mersenneforum.org/showth...810#post555810
I thank you for your patience.

As much TF data as there is flowing into Primenet every hour, keeping it for a year has to be a challenge. I try to stay away from it if I can. The older data being removed is why I didn't see anything on that particular exponent.

Something I noticed. The PRP assignments Prime95 reserves as it runs have a shorter format than manual reservations. A manual I got has ",99,0,3,0," where the automatics do not. I looked at assignment element breakdown you posted. Prime95 must not need these things as they are automatic for it.

So, I am running PRP-CF's with v30.3 Build 5, and P-1's with the latest gpuOwl. Why CF's one might ask? Many users do not like to run them, and I feel I do not have the CPU horsepower to run the large ones.
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