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Old 2010-03-17, 13:39   #1
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Default 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?
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Old 2010-03-17, 15:53   #2
R.D. Silverman
 
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Quote:
Originally Posted by Unregistered View Post
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?
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Old 2010-03-17, 16:02   #3
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Quote:
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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
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Old 2010-03-18, 02:42   #4
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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
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Old 2010-03-19, 01:00   #5
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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.
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Old 2010-03-19, 03:22   #6
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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.
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Old 2010-03-19, 04:01   #7
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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)!!!
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Old 2010-03-19, 04:04   #8
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Quote:
Originally Posted by joblack View Post
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.
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Old 2010-03-19, 14:35   #9
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Quote:
Originally Posted by retina View Post
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
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Old 2010-03-24, 17:53   #10
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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
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Old 2010-03-24, 20:16   #11
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Quote:
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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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