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Old 2018-07-12, 17:22   #1
ixfd64
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Default Mersenne.ca discrepancies

I recently noticed a few discrepancies with the Mersenne.ca database:

1. The entry for M87940961 shows that the minimum P-1 bounds are not calculated. I haven't seen this for any other exponent. Is there any reason for this?

2. The entry for M25153 incorrectly lists 95798344469709111399327318847787476387212693634994913715944997998172541010266957318247461159 as a prime factor. It's actually the product of the four currently known factors.
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Old 2018-07-12, 23:35   #2
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Quote:
Originally Posted by ixfd64 View Post
2. The entry for M25153 incorrectly lists 95798344469709111399327318847787476387212693634994913715944997998172541010266957318247461159 as a prime factor. It's actually the product of the four currently known factors.
It probably was accepted as a new factor because it was used in a PRP test:
https://www.mersenne.org/report_expo...exp_hi=&full=1
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Old 2018-07-21, 17:27   #3
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Same thing appears to be happening in

http://www.mersenne.ca/exponent/7508981
Code:
196390556749512365885553091471517315772448332119011812799224967043247355807885758998536981636538241093908075798179275216900756503990104076135107768463 
is not a prime factor
http://www.mersenne.ca/exponent/111269
Code:
2483611811780967729450526041810356652852620293014220023255782117303084384090070203366756119
97741873979710938487033764107284665796924065785506374732657395204556552490513667177770940383463688455655450791
92931654532319876438832186923672422729542099694851688102212583901293792387759635634014037818755101113436948191796372627855844302598713
are not prime factors
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Old 2018-07-21, 23:08   #4
James Heinrich
 
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Quote:
Originally Posted by ixfd64 View Post
I recently noticed a few discrepancies with the Mersenne.ca database
Please feel free to send me an email or PM if you notice any issues as I don't frequently browse the forum and wouldn't have seen this thread (thanks to GP2 for bringing it to my attention).

Quote:
Originally Posted by ixfd64 View Post
entry for M25153 incorrectly lists 957...159 as a prime factor
When new factors are submitted they are immediately checked for primality, but if they exceed a certain size (I believe I set it to ~200 bits) they are temporarily accepted and set aside for me to check manually. Unfortunately I was on vacation for a couple weeks and a typo in my verification code prevented the job from running so a few composites slipped in. I'm running a double-check now and removing composite factors. So far I have just found 5 factors for the three exponents mentioned in this thread (M25153, M111269 (x3), M7508981). If I find more I'll purge them too.

Quote:
Originally Posted by ixfd64 View Post
The entry for M87940961 shows that the minimum P-1 bounds are not calculated. I haven't seen this for any other exponent. Is there any reason for this?
A side-effect of the above-mentioned typo in the cron job that is tasked with such things. Once it finished the backlog the bounds should show up correctly.
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Old 2018-07-22, 02:35   #5
Prime95
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Even a one or two thousand bit PRP test should be pretty near instantaneous. Alternatively, attempting to divide by known factors would be very quick. Once setup, it would save you from manually handling big composites.
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Old 2018-07-22, 02:50   #6
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Both fair points. I'll see if I can work those ideas into the codeflow.
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Old 2018-08-03, 17:16   #7
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Quote:
Originally Posted by Uncwilly View Post
I am throwing a bunch of P-1 at 79777211 (I went to mersenne.ca and asked for the worktodo entry with a 5.5% chance of finding a factor.)
When doing the cut and paste of the exponent number (from the bit highlighted in the attachment) into the P-1 form, it lopped off the final '1'. I found this out because 7977721 already had a factor reported (which I rediscovered.)
Seems to be a problem in the code.

E-mail/pm will be sent.
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Old 2018-08-03, 21:04   #8
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I think I see what you're getting at. If you copy-paste the exponent with other characters in it (e.g. "M79,777,211") into the exponent field it would first limit the input to 9 characters, then remove the non-numeric characters, leaving you with a truncated value. I have removed the input length limit so it should work as expected now.
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Old 2018-08-03, 21:40   #9
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Old 2020-10-31, 05:14   #10
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https://www.mersenne.ca/exponent/3243941 has an invalid factor that is messing up here and here
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Old 2020-10-31, 11:40   #11
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Quote:
Originally Posted by axn View Post
https://www.mersenne.ca/exponent/3243941 has an invalid factor that is messing up here and here
Thanks, I have removed the invalid factor record. I have also fixed the code that was supposed to notify me about it but didn't.
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