multiple (3+) Unverified LL -- how common?

[Batalov]

Isn't it nice to have a record in something?
It was a database hiccup. Some V5 switchover childhood disease?
Ah, the good ol' days...

[mdettweiler]

Originally Posted by ckdo

It is actually "same random shift count" regardless of user and CPU.

So, if I'm understanding you correctly, someone could doublecheck their own first-time test, and have the result accepted as a full verification, as long as the shift count is different?

[ckdo]

Originally Posted by mdettweiler

So, if I'm understanding you correctly, someone could doublecheck their own first-time test, and have the result accepted as a full verification, as long as the shift count is different?

Yes. OTOH you can not simply create two accounts and submit all results twice. Compare here, for example.

[mdettweiler]

Originally Posted by ckdo

Yes. OTOH you can not simply create two accounts and submit all results twice. Compare here, for example.

Ah, makes sense. Thanks!

[Christenson]

Originally Posted by cheesehead

<snip> and even because of cosmic rays (seriously). If the GIMPS database had data on the altitude of each system that reported a result, we could probably see a small bias toward more errors from systems at higher altitudes -- seriously.

This might be a reasonable question to ask of a machine -- approximate elevation. That bias might provide a good measure of cosmic ray error frequencies! (But my machines at "robotics" might cheat...they live in the UVA (decomissioned) nuclear reactor building, and, while radiation is supposed to be close to background, I have no real proof of that)

[sdbardwick]

Originally Posted by patrik

When I downloaded the data for plotting the error rate on December 25, 2010, there were 376 exponents with three or more non-matching residues. Of these 14 have four or more non-matching residues, and one has five (41940097).

Just for fun I cleared 41940097.

[Christenson]

Originally Posted by sdbardwick

Just for fun I cleared 41940097.

That doesn't quite make sense --- do you mean you re-did the LL test and got a matching residue? That would take me a month and a half or so. Or did you get a factor from P-1 testing? Or something else?

I'm willing to let a core do some backup checking when there's a good reason like this, as soon as the next box is up and running.

[sdbardwick]

Double check LL on 4 cores of i5-2500k.

[S34960zz]

Originally Posted by Christenson

That doesn't quite make sense --- do you mean you re-did the LL test and got a matching residue? That would take me a month and a half or so. Or did you get a factor from P-1 testing? Or something else?

The link provided (http://mersenne.org/report_exponent/...&B1=Get+status) shows a full LL test by "Fade Out".

For those with enough cores and clock speed, it can be done.

27 Apr 11 01:38 sdbardwick reports "cleared"
23 Apr 11 08:52 patrik reports "5 failures for exponent 41940097"
====================
3 days 16.75 hours more-or-less, call it 3.67 days.

Using 3 of 4 cores i7-QM840 @ 1.87 GHz, I can clear a 26xxxxxx exponent in 87 to 90 hours (3d-15h to 3d-18h). Somebody using 4 or 6 cores and a clock twice as fast would have no problem turning around a 42xxxxxx exponent in that amount of time.

[James Heinrich]

Originally Posted by S34960zz

For those with enough cores and clock speed, it can be done.

The test takes 61.8GHz-days of work. A single stock-speed (3.3GHz) i5-2500K core should produce about 5.7GHz-days of work per day. Assuming decent scaling to 4 cores, that's ~22GHz-days/day, so under 3 days. If the i5 is overclocked to 4.6GHz (which is not too uncommon) it could be done in 2 days flat.

[S34960zz]

Originally Posted by S34960zz

One of my computers performed a double-check LL on an exponent 26,xxx,xxx. When the residue was submitted to PrimeNet, it did not match the first result, so both results were noted as "Unverified LL" and the exponent was assigned to a third computer for re-evaluation.

That third result was submitted a few days ago. None of the first three residues match, and the exponent is presently out for its fourth LL test.

Follow-up: the 4th LL result [07-June] matched the 2nd LL result (my contribution). Two matching LL, two non-matching LL.
http://www.mersenne.org/report_expon...&B1=Get+status

And ... it's not prime.