20100907, 01:01  #1 
Aug 2004
Melbourne, Australia
2^{3}×19 Posts 
Seeking a proof that 5^7954+7954 is prime
Hi guys,
Could someone please prove that 5^7954+7954 is prime? This question came up on math.stackexchange.com (here is the question). I won't be able to run Primo for long enough due to travelling.  Dougy 
20100907, 02:42  #2 
Aug 2006
3×1,987 Posts 
It's a BPSW probable prime, and a strong pseudoprime to 100 randomlyselected bases. I don't have the resources to prove it at the moment, but it's almost surely prime (even if selected by an adversary).

20100907, 07:26  #3  
"Frank <^>"
Dec 2004
CDP Janesville
4112_{8} Posts 
Quote:


20100907, 11:29  #4 
Oct 2007
Manchester, UK
2·3·223 Posts 
I've started it on a core of a 2.4 GHz Core 2 Duo PC, shame Primo isn't multithreaded.
I guesstimate around 37 days runtime based on info here: http://mathworld.wolfram.com/Ellipti...tyProving.html Through simple clock speed scaling, I guesstimate 30 days running on your 3 GHz Pentium D. I suppose it does somewhat depend on how Primo has been updated and optimised to run on the Core architecture. Does anyone have any better estimates? The number is 5560 digits or 18469 bits in length. 
20100907, 11:55  #5 
Mar 2006
Germany
2×1,433 Posts 
See this thread with some useful hints from Cybertronic aka Norman Luhn (see posts 127 and 166).
Perhaps he can help out here! 
20100907, 12:22  #6 
Aug 2004
Melbourne, Australia
230_{8} Posts 
Thanks for that, that's great! In either case, it would be significantly faster than if I ran it myself.

20100907, 13:19  #7 
Oct 2007
Manchester, UK
2×3×223 Posts 
kar_bon, I think I managed to make some sense of post 127, using a pair of translators to compensate for each others deficiencies. However, I don't think I'll bother hacking into the intermediate files of Primo as I don't understand anywhere near enough about it for that. I'd almost certainly end up wasting weeks of CPU time computing nonsense.

20100908, 07:54  #8 
"Frank <^>"
Dec 2004
CDP Janesville
2122_{10} Posts 
I hadn't estimated yet, but I knew it was going to be slow after it didn't advance any bits after seven hours...I would have had to kick one of my sieve jobs off a faster core to make any progress.

20100908, 08:41  #9 
Oct 2007
Manchester, UK
2×3×223 Posts 
Here's where mine is after nearly a day of running.
Edit: I should point out that I have basically no idea what any of the status info means. Last fiddled with by lavalamp on 20100908 at 08:45 
20100908, 09:18  #10  
"Frank <^>"
Dec 2004
CDP Janesville
2122_{10} Posts 
Quote:
Two things: if you want to use the PC at all, check the "Idle" box, otherwise Primo will monopolize the CPU; and check the "Double file management" box if you don't have a UPS, that way Primo will keep backups of the temp files as it works, just in case the power were to quit while it was writing a file. 

20100908, 09:37  #11  
Oct 2007
Manchester, UK
2·3·223 Posts 
Quote:
As far as the idle box, I deliberately unchecked that one so that it can pretty much have the core all to itself and not have to give way. It's a dual core machine and nothing else it does will max out the other core. 

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