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1)
Message boards :
General discussion :
Extended generalized Fermat prime?
(Message 146710)
Posted 904 days ago by  Gelly
ECPP is achingly slow. There is a reason the official version of primo only goes up to 50k decimal digits. The current record, 40k digits, was set by Paul Underwood on 48 thread hardware that took more than a year and was nothing to sneeze at. My 3970x threadripper, a 32 core, 64 thread beast, takes two weeks to months to prove candidates in the 20k digit range.
As a rule of thumb, when you double the amount of digits in the number to be tested, the time it takes goes up 16 to 32 times, depending on how lucky you are. It will likely be years before Paul proves the next big step in ECPP (the smallest unproven repunit, 49k digits), and I'm sure he either got a 3990x (64 cores!) or maybe even doshed out on EPYC.
100k digits, on current hardware with current methods, would take decades.
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2)
Message boards :
General discussion :
b^n - b^m - 1 primes
(Message 145537)
Posted 929 days ago by Gelly
It actually would not be a Proth number. For a generalized Proth number k*b^n + 1 (or Thorp, k*b^n-1), the requirement is that k < b^n. For the rearrangement you provided, where k = b^(n-m)-1, it will not necessarily be true that k < b^m (such as when n-m > m)
Edit: Concerning your original question, programs usually have a limit on the size of k that are acceptable to test. With a different form, you don't have to fight with the k requirement.
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3)
Message boards :
General discussion :
Current number of tests for a prime?
(Message 145013)
Posted 945 days ago by Gelly
The only number I know for sure, based on empirical evidence, is that finding or DCing an SGS prime tends to happen after about 15k tasks. The other ones are a lot harder to get good numbers for, since they happen more rarely.
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4)
Message boards :
Number crunching :
Sieve for palindromic primes?
(Message 144796)
Posted 953 days ago by Gelly
Doing a lot of hunting on MersenneForums, Batalov indicated that the sieve he wrote was "quick n' dirty in Pari", PARI/GP being a mathematical programming/scripting language.
The reason that they are a little bit more convoluted (10^(2n)+999*10^(n-1)+1) is because if the form is too simple, it's liable to be divisible by numbers for a vast majority of exponents - see https://oeis.org/A187868 for a similar example.
I'm not certain on the precise particulars of how you'd quickndirty sieve in Pari. It looks to be a form that's a little more complicated than just figuring out what n lead to being non-prime for different p, like what you can do for k*b^n +- 1 with BSGS.[/url]
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5)
Message boards :
Number crunching :
Badges III
(Message 144679)
Posted 958 days ago by Gelly
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6)
Message boards :
Number crunching :
WW testing
(Message 144389)
Posted 963 days ago by Gelly
Seems like robish was rearing to go on some Nvidia-X test, so I'll also reserve CPU multithreading for Linux (with a 3970x, no less!)
Done!
CRC 1) 67029FBFBC1AEFB0
CRC 2) 2F32CAD23BA5B1CA
CRC 3) B8B040FA3813FEB2
Same thing as my Nvidia results. Checkpointed a lot more often, though, and failed to give an ETA at checkpoints like Nvidia did. Likely more down to implementation than any bugs.
The 3970X at 64 threads kept up with or outperformed the GTX 960 in terms of time, which is probably the wildest thing I've seen for CPU vs. GPU. Probably due to the fact that, once you get past 16 cores, the CPU gets closer to being a GPU than anything else.
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7)
Message boards :
Number crunching :
WW testing
(Message 144387)
Posted 963 days ago by Gelly
Seems like robish was rearing to go on some Nvidia-X test, so I'll also reserve CPU multithreading for Linux (with a 3970x, no less!)
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8)
Message boards :
Number crunching :
WW testing
(Message 144386)
Posted 963 days ago by Gelly
I can reserve Nvidia-Linux
Done!
CRC 1) 67029FBFBC1AEFB0
CRC 2) 2F32CAD23BA5B1CA
CRC 3) B8B040FA3813FEB2
The special instances expected in the document seemed to line up pretty well (test 2 also nabbed the two wieferich primes).
Done with a GTX 960 in a decent amount of time.
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9)
Message boards :
Number crunching :
WW testing
(Message 144383)
Posted 963 days ago by Gelly
I can reserve Nvidia-Linux
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10)
Message boards :
Number crunching :
Évariste Galois's Birthday Challenge
(Message 144064)
Posted 973 days ago by Gelly
Any bets how many DIV primes we will find during the five days? /JeppeSN
I will invest an absurd amount of my personal time and money to get as close to ensuring at least one prime as I can.
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