mersenneforum.org  

Go Back   mersenneforum.org > Great Internet Mersenne Prime Search > PrimeNet

Reply
 
Thread Tools
Old 2012-04-24, 08:28   #1
Dubslow
Basketry That Evening!
 
Dubslow's Avatar
 
"Bunslow the Bold"
Jun 2011
40<A<43 -89<O<-88

722110 Posts
Default Three matching tests not closing exponent?

http://mersenne.org/report_exponent/?exp_lo=25956701

The first two could easily be suspicious (and I've DCd one of my own expos, different hardware), but surely the third test puts the case to rest? I'd rather not test it if I don't have to.
Dubslow is offline   Reply With Quote
Old 2012-04-24, 08:42   #2
Batalov
 
Batalov's Avatar
 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

2·4,591 Posts
Default

Someone was phishing for the last two hex-digits and didn't get lucky before being blocked by the server?



It would only take 256 tries to successfully "verify" any residue! Why do you assume that these three have the censored digits matched?

Last fiddled with by Batalov on 2012-04-24 at 08:46
Batalov is offline   Reply With Quote
Old 2012-04-24, 08:43   #3
aketilander
 
aketilander's Avatar
 
"Åke Tilander"
Apr 2011
Sandviken, Sweden

2×283 Posts
Default

Quote:
Originally Posted by Dubslow View Post
http://mersenne.org/report_exponent/?exp_lo=25956701

The first two could easily be suspicious (and I've DCd one of my own expos, different hardware), but surely the third test puts the case to rest? I'd rather not test it if I don't have to.
My guess is that all three tests have the same shift count and therefore the value is only equal to one test. That is, most probably it is not three independant tests, so I would guess that the same user have done all three tests. Maybe his computer broke and he continued from a backup copy without knowing that the result had already been reported and maybe he changed username when he reinstalled Prime95.

Or maybe he installed the program on three different computers starting with a backup-copy with the expo half-way through.

So in order to safely clear the exponent a 4th test is needed.

Last fiddled with by aketilander on 2012-04-24 at 08:57
aketilander is offline   Reply With Quote
Old 2012-04-24, 09:21   #4
LaurV
Romulan Interpreter
 
LaurV's Avatar
 
Jun 2011
Thailand

2·4,481 Posts
Default

Al in all, this is quite ok, and makes me feel good, safe, regardless of whatever the reason is. In the sense there are no false-negatives in the database (i.e. missed primes :P). If we are about to eliminate an exponent, then let's be completely sure the associated mersenne number is composite...

Last fiddled with by LaurV on 2012-04-24 at 09:25
LaurV is offline   Reply With Quote
Old 2012-04-26, 19:31   #5
Dubslow
Basketry That Evening!
 
Dubslow's Avatar
 
"Bunslow the Bold"
Jun 2011
40<A<43 -89<O<-88

160658 Posts
Default

All previous tests had the same matching last two bits.

http://mersenne.org/report_exponent/?exp_lo=25956701
Edit: The chances of them having the same shift value is astronomically small. (That's randomly produced at runtime.)

Last fiddled with by Dubslow on 2012-04-26 at 19:31
Dubslow is offline   Reply With Quote
Old 2012-04-27, 09:45   #6
aketilander
 
aketilander's Avatar
 
"Åke Tilander"
Apr 2011
Sandviken, Sweden

56610 Posts
Default

Quote:
Originally Posted by Dubslow View Post
All previous tests had the same matching last two bits.

http://mersenne.org/report_exponent/?exp_lo=25956701
Edit: The chances of them having the same shift value is astronomically small. (That's randomly produced at runtime.)
Yes you are right, the shift value should, most probably, be different if the three tests were independant, but if the second and third test really started with an intermediary file or backup file at, lets say, iteration 25000000 (on a different computer) then I suppose the shift value would be the same and the server would recognize it. (this is my guess) So my guess is that's the reason why the exponent wasn't cleared after three tests is that they had the same shift count showing that the three test were in fact only 1 complete test. But on the other hand I can be wrong!

I would be happy if someone with better insight in these matters could tell us how it works.
aketilander is offline   Reply With Quote
Old 2012-04-27, 16:58   #7
Dubslow
Basketry That Evening!
 
Dubslow's Avatar
 
"Bunslow the Bold"
Jun 2011
40<A<43 -89<O<-88

3×29×83 Posts
Default

Quote:
Originally Posted by aketilander View Post
Yes you are right, the shift value should, most probably, be different if the three tests were independant, but if the second and third test really started with an intermediary file or backup file at, lets say, iteration 25000000 (on a different computer) then I suppose the shift value would be the same and the server would recognize it. (this is my guess) So my guess is that's the reason why the exponent wasn't cleared after three tests is that they had the same shift count showing that the three test were in fact only 1 complete test. But on the other hand I can be wrong!
I'd buy that for the first two, since the username is similar, but the third one as well?

I suppose though this makes the most sense out of the running suggestions.
Quote:
Originally Posted by aketilander View Post
I would be happy if someone with better insight in these matters could tell us how it works.
Yes me too please (Perhaps someone with special database access? )
Dubslow is offline   Reply With Quote
Old 2012-04-27, 17:40   #8
bcp19
 
bcp19's Avatar
 
Oct 2011

10101001112 Posts
Default

Quote:
Originally Posted by Dubslow View Post
I'd buy that for the first two, since the username is similar, but the third one as well?

I suppose though this makes the most sense out of the running suggestions.
Yes me too please (Perhaps someone with special database access? )
If you look through the top producers usernames, there are several S5.... usernames, and a search of Carlo turned up a CarloS56, so coincidence?
bcp19 is offline   Reply With Quote
Old 2012-04-27, 18:19   #9
Batalov
 
Batalov's Avatar
 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

2·4,591 Posts
Default

These S##### handles were, I believe, bestowed to very early users by the server. Some of them are proudly worn even here, on the forum.

It looks like the savefile was passed on to friends to boost their ratings or something like that. Someone may have a look into other tasks given to the same userids (but then again they may have done only one job, "got bored" and left).
Batalov is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Largest number of LL tests before matching residues achieved? sdbardwick Lounge 1 2015-02-03 15:03
Can 1227133513 be the only composite number matching the conditions? miket Math 5 2014-08-12 00:41
Residue not matching due to masked bits patrik Data 1 2011-09-24 23:44
Planet closing in causing my family's bad luck ? science_man_88 Astronomy 16 2010-09-21 03:44
Closing Older Threads to Thwart Spammers Prime Monster Forum Feedback 0 2004-10-24 23:47

All times are UTC. The time now is 21:08.

Thu Dec 3 21:08:18 UTC 2020 up 17:19, 1 user, load averages: 1.95, 1.94, 2.00

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.