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Old 2016-01-29, 03:02   #1
bgbeuning
 
Dec 2014

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One of my machines recently finished a double check and apparently
the residue did not match. I go look at the details for this exponent

http://www.mersenne.org/report_expon...9761383&full=1

and it has had three LL tests run and none of the residues match.
Does this happen a lot?

Trivia question: Which exponent has had the most number of
(unmatching residue) LL tests done on it? (I don't know.)
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Old 2016-01-29, 03:08   #2
Mark Rose
 
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It happens often enough. It's not unusual to need a quad check.
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Old 2016-01-29, 03:19   #3
Dubslow
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Most or all of those questions have been answered at some point in time in this thread: http://mersenneforum.org/showthread.php?t=20372

Of course, I couldn't tell you *where* in the thread the answers lie. Perhaps madpoo would have better luck refreshing our memories.

Suffice it to say, as Mark indicates, quad checks are surprisingly common, I think more than 10 per 1M exponent range, possibly even up to a hundred.

I think the most mismatches is somewhere around 6, though I may be recalling incorrectly.
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