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-   -   69 * 2^n - 1 (https://www.mersenneforum.org/showthread.php?t=18600)

Kosmaj 2014-01-14 22:50

Hi diep,

Yes, there is a jump in the length of the used FF transform, from about 144k to 160k, at n=2750k.

The next jump to 192k will appear at n=3274k.

diep 2014-01-14 23:06

Ah many thanks!

So the next jump makes it extra tough to find stuff of 1M digits :)

After a slow start first few months, it's 16 cores now which went steady, yet i guess i soon have to increase that to 32+ cores to keep the momentum because of the huge slowdowns.

Too bad i can't throw into battle the gpu's yet.

Know a description of how it works with this fft len size and the used transform?

I have a book from Pomerance & Crandall, yet those descriptions are not very usable to write code from and so far it seems one of the few books at least attempting to describe something :)

The FFT i implemented a few years ago, it works in a power of 2 larger. So to calculate n limbs one needs an array sized 2n limbs, which simply would mean a single 8 core box is same speed like 1 GPU, instead of the GPU being roughly 5x faster (Tesla C2075's i have here) or more than a single 8 core Xeon box here :)

pinhodecarlos 2014-01-15 11:27

Hi diep,

I found this: 69*2^2428251-1 is prime! (730979 decimal digits) Time : 2077.484 sec.

HEHEHEHEHEHE

diep 2014-01-15 14:06

Congratulations!

diep 2014-01-15 14:14

Did you finish it now to 2.5M?

As i started at 2.5M as appointed.
It's testing to 3M here now in the current batch.

pinhodecarlos 2014-01-15 14:48

[QUOTE=diep;364613]Did you finish it now to 2.5M?

As i started at 2.5M as appointed.
It's testing to 3M here now in the current batch.[/QUOTE]

It is a RPS drive, I am not testing it alone.
Check progress here: [url]http://www.mersenneforum.org/showthread.php?t=14087[/url]

diep 2014-01-15 14:53

Maybe you find another few primes there, let's hope so!

As for 69, note after this 2.41M find i hadn't expected in the range till 3M for another 2 at least to be there!
I thought: "maybe there is one around 2.8Mbit".

Yet already 2 showed up now :)

diep 2014-04-15 23:23

Last cores will take some time to finish yet 3M nearly completed.
Divided 3M-4M into pieces. Cores already busy short while there.

Maybe the gem shows up as the last to be checked!

All machines being equipped with ECC is tough to blame on a bitflip in RAM :)

If the crashed internet machine here fixed and other IT stuff might have look at CUDA again for doing Riesel with it.

diep 2014-05-09 22:30

Prime!

69 * 2 ^ 3097340 - 1 is prime

Please can one or more try to verify?

Thanks,
Vincent

pinhodecarlos 2014-05-09 23:25

If you trust your hardware just submit it. Only within an hour I will have an open slot to test this number.

paulunderwood 2014-05-09 23:25

[CODE]69*2^3097340-1 is prime! Time : 2579.994 sec.[/CODE]

Well done! :toot:


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