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 2010-03-17, 13:39 #1 Unregistered   23×1,187 Posts 100M digit prime How long would it take for a supercomputer to check a 100M digit number? Could a dedicated computer be built to test 100M digit numbers at a rate of one per month? If yes, any guess on cost?
2010-03-17, 15:53   #2
R.D. Silverman

"Bob Silverman"
Nov 2003
North of Boston

23·937 Posts

Quote:
 Originally Posted by Unregistered How long would it take for a supercomputer to check a 100M digit number? Could a dedicated computer be built to test 100M digit numbers at a rate of one per month? If yes, any guess on cost?
A. It depends on the size of the supercomputer.
B. Yes;
C. Yes, we can guess at the cost.

Why anyone would dedicate a machine to such an effort is beyond me.
Even more mysterious would be why anyone would spend money on it.

Finding such a prime would not solve any open problems. It has little
value beyond entertainment. We know such primes exist. Finding one
will happen eventually. What's the hurry?

2010-03-17, 16:02   #3
Mini-Geek
Account Deleted

"Tim Sorbera"
Aug 2006
San Antonio, TX USA

10000101101112 Posts

Quote:
 Originally Posted by Unregistered How long would it take for a supercomputer to check a 100M digit number?
What supercomputer?
Unfortunately, the LL test does not scale linearly (since you must complete each iteration in order), with basically-marginal gains at 8 or greater cores. I'm not sure if any current supercomputer could complete one in one month, though you could certainly average a much greater throughput with enough firepower (as long as you're willing to wait months to years to get results).

A better approach than a supercomputer might be a farm of quad (or hex, or dual quad, or something like that) core computers. My i5 (quad core running at 2.8 GHz) could do one 100M digit Mersenne number in about 600 days (using all cores). To complete 20 every 600 days (an average of one per month), you'd need a cluster of 20 such computers. You might be able to get down to $300-$400 per computer. That's $6,000 to$8,000, plus electricity (which is not a trivial cost).
Of course, if you are serious about doing this, you'll want research other computer combinations, look around for the best prices, look into what sort of software you'll want to use and how it scales, etc. etc.
Or you could just wait about 10 years (rough guesstimation) and buy one desktop computer for a few hundred bucks that can complete a 100M digit LL every month.
And, like Silverman said, there's no good reason to dedicate so much money towards something that can wait a few years and would solve no problems (just provide some entertainment).

Last fiddled with by Mini-Geek on 2010-03-17 at 16:06

 2010-03-18, 02:42 #4 joblack     Oct 2008 n00bville 25·23 Posts Silverman the ever lasting misanthropist. The question is not if it is possible but if you can buy such a device. You would have to program it for a graphic card array or buy a 6+ core. An overclocked Core i7 would be a fine hardware for a low price. An Intel Corei7 980x would be a nice hardware to try prime95 but with almost 1.000 bucks a little bit pricey (perhaps not?) Last fiddled with by joblack on 2010-03-18 at 02:45
2010-03-19, 01:00   #5
lfm

Jul 2006
Calgary

52·17 Posts

Quote:
 Why anyone would dedicate a machine to such an effort is beyond me. Even more mysterious would be why anyone would spend money on it.
I suspect the poster and others like him/her are motivated/misled by the EFF prize. They think they can "win" some money and no one else has thought of it before and actually estimated the expense and compared it to the chance of payoff.

2010-03-19, 03:22   #6
joblack

Oct 2008
n00bville

73610 Posts

Quote:
 Originally Posted by lfm I suspect the poster and others like him/her are motivated/misled by the EFF prize. They think they can "win" some money and no one else has thought of it before and actually estimated the expense and compared it to the chance of payoff.
It's more about the fame. In a few years for the 50.000 USD you will be able to buy a pizza and two colas.

2010-03-19, 04:01   #7
petrw1
1976 Toyota Corona years forever!

"Wayne"
Nov 2006

3·5·349 Posts

Quote:
 Originally Posted by joblack It's more about the fame. In a few years for the 50.000 USD you will be able to buy a pizza and two colas.
Yeah but a 3-topping pizza and a real cola (not diet or zero any anything like that)!!!

2010-03-19, 04:04   #8
retina
Undefined

"The unspeakable one"
Jun 2006
My evil lair

29×229 Posts

Quote:
 Originally Posted by joblack In a few years for the 50.000 USD you will be able to buy a pizza and two colas.
You can already buy that today with $50k. I think you are shopping at the wrong places. 2010-03-19, 14:35 #9 joblack Oct 2008 n00bville 25·23 Posts Quote:  Originally Posted by retina You can already buy that today with$50k. I think you are shopping at the wrong places.
I'm referring to the upcoming hyperinflation after the 2nd Great Depression ;).

Last fiddled with by joblack on 2010-03-19 at 14:40

 2010-03-24, 17:53 #10 Unregistered   7×383 Posts i got a core i7 but prime 95 still running using only 65 mbs of ram how can i do to make it increse the limit is set in 3096 mb
2010-03-24, 20:16   #11
petrw1
1976 Toyota Corona years forever!

"Wayne"
Nov 2006

10100011100112 Posts

Quote:
 Originally Posted by Unregistered i got a core i7 but prime 95 still running using only 65 mbs of ram how can i do to make it increse the limit is set in 3096 mb
Depends on the work you are doing:

The only work types that NEED and will use more than a few meg are P-1 Factoring and ECM (either type) ....and then only in Stage 2 of the processing...they will at most use what you set using the:
Code:
Options
CPU...
screen.

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