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An anonymous reader writes "The Great Internet Mersenne Prime Search (GIMPS) has apparently discovered a new world-record prime number. A GIMPS client computer reported the number on August 23rd, and verification is currently under way. The verification could take up to two weeks to complete. The last Mersenne prime discovered was over 9.8 million digits long, strongly suggesting that the new value may break the 10 million digit barrier — qualifying for the EFF's $100,000 prize!"

...is a list of all the prime numbers whose length in number of digits is also a prime number as well. I wonder if anyone has found any really big ones of those.

Re:What would really be neat... (5, Insightful)

Anonymous Coward | more than 6 years ago | (#24773867)

That is kinda less interesting because it depends on the system used to represent the number (binary, decimal, etc.) rather than an intrinsic property of the number

5 years ago few believed that a simple prime number could be calculated to 10 million digits. There was a lot of scepticism that a prime number could be calculated so large. A prime number, calculated to 10 million digits?? pfft. But now, 5 years later GIMPS has calculated Mersenne primes over 9 million digits using computers of all ages, all over the world. That's because GIMPS is scientifically proven to work. It's not a gimmick.

...
(Random interviews)
Q: What happened when you participated in the GIMPS project?
A: Ah.. It got bigger.
Q: And you're not embarassed to say that?

But when it comes to primes in the 10 million digit range (I couldn't even guess how many bits you would require for a number that large), it becomes impractically large for cryptography.

From the GIMPS website:

Finding new Mersenne primes is not likely to be of any immediate practical value. This search is primarily a recreational pursuit. However, the search for Mersenne primes has proved useful in development of new algorithms, testing computer hardware, and interesting young students in math.

Because it's 2^n-1 it'd be 1111111....1111111 (the prime number is entirely made of 1s in base 2). So there's way less than 31MB of information in the number

Re:Forgive my ignorance (0)

Anonymous Coward | more than 6 years ago | (#24773961)

So if it's exactly 10 million digits long, then you could represent it as "10011000 10010110 10000000" (binary for ten million) with an extra 8-bit byte to signify context. A single 32-bit sequence could store any Mersenne Prime up to one with 16,777,215 digits.

Re:Forgive my ignorance (0)

Anonymous Coward | more than 6 years ago | (#24773749)

It takes about 33 million bits, and get this - each and every one of those bits is 1. Not a single zero in the lot!

Oh hells yeah!!! (2, Funny)

Anonymous Coward | more than 6 years ago | (#24773877)

I do IT-support in the school district...let me tell you:

...and interesting young students in math.

The kids were in a veritable state of mathematics riot today.

Smoking pot, getting laid, and blowing off responsibility is so not punk rock.

God...do these guys realize how embarrassing they make adulthood?

right (2, Funny)

Anonymous Coward | more than 6 years ago | (#24773549)

Since this is a particularly good prime, we should standardize on it. That way we wouldn't have to find our own ones every time we want to use RSA.

I'm pretty sure that in the past, the government would pay money for large prime numbers to use for encoding purposes. I don't know if they still do but they used to pay 1000 dollars (I think it was 1000) for primes over 100 digits.

They don't, at least for numbers that small. If they did, you could take a copy of ssh-keygen and a second-hand computer and make millions in fairly short order.

I think the real question is why it is worth $100k. I'd sure be interested to know, especially seeing that my system can probably attempt to find prime numbers pretty damn quick if it's a threaded app.

It goes towards the enormous knowledge on prime number theory.

The problem of if there is a pattern to the sequence of prime numbers is unknown. That is, if I ask you what is the 69th prime number, the only known general algorithm is to computer the 1st prime, 2nd prime and so on until the 69th prime. And, also there are unsolved problems with Mersenne primes as well.

So, if someone comes up with a good theory, then it's good to have some big examples.

And, in case you didn't know, prime number theory is used in cryptography.

And who gets the prize, GIMPS or the person running the client?

If it's the latter i'll go download the client right now.

Re:Forgive my ignorance (0)

Anonymous Coward | more than 6 years ago | (#24773965)

The client, but consider that it is taking them two weeks to test this one number. It's kind of like entering the lottery, only the ticket is almost entirely free (sans electricity costs).

You seem to misunderstand the meaning of prime [wikipedia.org] . Either that, or you're a horrible comedian. In either case, 77 isn't prime, and neither is 77777777.

However, even if a string of 7's were prime, that may not be enough. As stated previously, if n = 2^x - 1 is prime, then x must be prime. However, the converse is not true. That is, x being prime does not guarantee that n is prime. E.g., if x = 11, then n = 2^{11} - 1 = 2047 = 23 x 89.

Depends. Is your day job working as a mathematician?:)

Re:Well, I just beat them! (0)

Anonymous Coward | more than 6 years ago | (#24773471)

if n = 2^x - 1 is prime, then x must be prime

If that's true, can't we just solve for x and work backwards? (Since x must be prime, we would know we have a prime that way) It's been awhile, but I am pretty sure you can solve for x using logorithms or something.

Re:Well, I just beat them! (0)

Anonymous Coward | more than 6 years ago | (#24773419)

Well now, as the summary points out, it could be less than 10 million digits. For instance, it could be the previous record holder plus one. My calculator only goes up to 8 digits, so I can't test it one way or another.

You say that, but at some point someone told me that 1 is a prime number and 2 is as well, so therefore, prime numbers can be one prime number plus 1. Plus, I'm a biologist.

You shouldn't think like that. Just think about your question, seriously. Whatever we do is pointless and useless and everything will be destroyed eventually through the heat death of the universe.

That being said, all that is important is that you have fun doing whatever you do. Believe it or not, some people really dig maths. Also, it's one more thing the species knows.

Re:I dont understand why this is important (4, Funny)

Testing a single 10,000,000 digit number takes two months on a 2 GHz Pentium 4 computer

According to their own benchmark pages a newer Core 2 Duo E8500 process in less than 21 days. Just recently I know that password cracking programs were written to use GPU's which dramatically increased the performance. Wouldn't writing code to run this on the GPU's result in even faster processing times?

GPU performance is geared towards floating point and massively parallel operations on small numbers. Unfortunately, neither of those characteristics are particularly handy for dealing with large primes.

Even in the general computing scenarios where they are useful, they are frequently wasting a lot of resources to accomplish the task. The Folding@Home team has noted that due to poor random access performance it is usually more efficient to recompute values than to retrieve them from memory. In practice, this means the seemingly awesome power of the GPU is often reduced by orders of magnitude relative to an equivalent ops/sec rating on a CPU.

The Lucas-Lehmer test for Mersenne primes consists of repeated multiplication (modulo a fixed large number). Large-integer multiplication is done via floating-point FFT, which is nothing but massive amounts of operations on small numbers. I don't know how FFT implementations for GPUs compare, but intuitively I think they ought to be at least as fast as for CPUs. The primes tested by GIMPS are small enough to fit entirely in GPU memory, so latency doesn't seem like a problem.

(I don't really know much about any of this, so feel free to correct/enlighten me.)

Re:GPU's? (0)

Anonymous Coward | more than 6 years ago | (#24773425)

Of course. The only issue with GPU processing is the proprietary and ever-changing architectures.

You generally don't see 3 or more gpu's successively that utilize the same architecture.

GPUs are much better suited to such a task than cpus, if support were equal.

Re:GPU's? (0)

Anonymous Coward | more than 6 years ago | (#24773983)

The hardware in GPUs is optimized for single-precision floating point calculations, but LL testing for Mersenne primes requires double precision FP calcs, meaning that whatever advertised FLOPS for a GPU will be different than any implementation of LL testing.

There are several threads about this on mersenne forums, and the amount of work required to get it to run on a GPU client would not be worth the marginal (if any) performance gain. A GPU works a lot better for Folding@Home calculations than for LL testing. As far as my understanding goes, anyway (which is probably flawed)

Anonymous Coward | more than 6 years ago | (#24774009)

Testing a single 10,000,000 digit number takes two months on a 2 GHz Pentium 4 computer

According to their own benchmark pages a newer Core 2 Duo E8500 process in less than 21 days. Just recently I know that password cracking programs were written to use GPU's which dramatically increased the performance. Wouldn't writing code to run this on the GPU's result in even faster processing times?

That depends on how long it takes to write the code...

Sure, you are excited now, but I predict you will look back on this moment with indifference once the 46th is discovered. For now, I'm going to keep the champagne on ice.

I predict that the last digit will be... (5, Funny)

I guess there's some room to ask... (2, Interesting)

Anonymous Coward | more than 6 years ago | (#24773547)

... why the EFF considers it worth $100,000 of donated funds to pay someone for finding a 10,000,000-digit prime number. That is not what my donations were intended to do.

Go fix warrantless wiretapping, then go looking for prime numbers, kthxbye.

Re:I guess there's some room to ask... (4, Informative)

(Prize money comes from a special donation provided by an individual EFF supporter, earmarked specifically for this project. Prize money does NOT come from EFF membership dues, corporate or foundation grants, or other general EFF funds.)

Still, it's not hard to think of some more, well, "electronic frontier-ish" applications for that kind of money. The FPGA-based DES keysearch engine they built a few years back was cool. OTOH, this Mersenne prime business just sounds like they're paying for something that will become trivial soon enough anyway.

Umm, that prize money was from a single donation that was made fir the precise purpose of funding this search. They are not using any other donations for this purpose. (I'm betting it was a half million dollar donation (or perhaps a full million dollar donation) made with the condition that part of it be reserved for this purpose. But the remainder of the donation would still be too large for the EFF to ignore.

Re:I guess there's some room to ask... (0)

Anonymous Coward | more than 6 years ago | (#24773719)

(Prize money comes from a special donation provided by an individual EFF supporter, earmarked specifically for this project. Prize money does NOT come from EFF membership dues, corporate or foundation grants, or other general EFF funds.)

(Prize money comes from a special donation provided by an individual EFF supporter, earmarked specifically for this project. Prize money does NOT come from EFF membership dues, corporate or foundation grants, or other general EFF funds.)

They didn't because it turns out the number is 7. The math crowd are really embarrassed that they missed it when they were checking the first time.

"Look, no one searches for Mersenne Primes down there, because we all know they've been found. That someone made a typo and left out 7 went undiscovered for years. We don't like to talk about it."

I think that should read 980,000 digits, not 9.8 million (see the list at Wikipedia [wikipedia.org] ), and 1 million digit mark, not 10 million (see linked EFF page).

The number of primes less than x is roughly equal to x/log(x). I think the implication is that, for numbers with 10 million digits, about one in every five million is prime. Since it took 6 days to verify that this new number is prime, you can see why they are concentrating on the mersennes instead of just checking numbers at random.

I think big prime numbers are a clue. I just don't know what they are a clue to.

We are currently turning our sieve in a method for rapidly factoring semi-prime numbers. Digital root mechanics have certain properties that make it easy to identify semi-prime candidacy positions in a by-9 table of the natural numbers.

A PDF at the bottom of the above-linked site explains our latest investigation of solving for [p, q] where n = p*q. The source code on the page is our prime sieve implemented in Perl.

Big Money! No Whammy! You, too, could become a hundred-millionaire M.O.H.'ing RSA to the ground!!

Known prime found? (0)

Anonymous Coward | more than 6 years ago | (#24773787)

45th Known Mersenne Prime Found

...in the Wikipedia article for Mersenne Primes?

I bet it'll be really exciting if one day they stumble upon a previously unknown Mersenne prime!

## Forgive my ignorance (0)

## Iamthecheese (1264298) | more than 6 years ago | (#24773045)

## Re:Forgive my ignorance (5, Funny)

## fractic (1178341) | more than 6 years ago | (#24773065)

To what use will this long, long prime be put?

Absolutely none whatsoever. That's the beauty of mathematics.

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773225)

That's ridiculous. Being useless is not what makes math beautiful. There are plenty of useless things that aren't beautiful.

## Re:Forgive my ignorance (5, Insightful)

## fractic (1178341) | more than 6 years ago | (#24773231)

## Re:Forgive my ignorance (5, Insightful)

## srjh (1316705) | more than 6 years ago | (#24773551)

"Physics is like sex. Sure, it may give some practical results, but that's not why we do it." - Richard Feynman

I'm guessing it's the same logic at work here.

## What would really be neat... (3, Funny)

## Nick Driver (238034) | more than 6 years ago | (#24773681)

...is a list of all the prime numbers whose length in number of digits is also a prime number as well. I wonder if anyone has found any really big ones of those.

## Re:What would really be neat... (5, Insightful)

## Anonymous Coward | more than 6 years ago | (#24773867)

That is kinda less interesting because it depends on the system used to represent the number (binary, decimal, etc.) rather than an intrinsic property of the number

## Re:What would really be neat... (1)

## postermmxvicom (1130737) | more than 6 years ago | (#24773943)

## Re:Forgive my ignorance (0, Offtopic)

## Majik Sheff (930627) | more than 6 years ago | (#24773283)

see also: Paris Hilton

## Re:Forgive my ignorance (5, Insightful)

## AndroSyn (89960) | more than 6 years ago | (#24773527)

I guess some of us have different standards on beauty...

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773555)

You must be new here.

## Re:Forgive my ignorance (1)

## Flyin Fungi (888671) | more than 6 years ago | (#24773765)

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773067)

Changing distant lightbulbs.

## Re:Forgive my ignorance (0, Offtopic)

## HaeMaker (221642) | more than 6 years ago | (#24773139)

Male enhancement.

## Re:Forgive my ignorance (4, Funny)

## martinw89 (1229324) | more than 6 years ago | (#24773533)

...

(Random interviews)

Q: What happened when you participated in the GIMPS project?

A: Ah.. It got bigger.

Q: And you're not embarassed to say that?

## Re:Forgive my ignorance (5, Funny)

## Miseph (979059) | more than 6 years ago | (#24773903)

That has to be one of the best penis pill ad spoofs I've ever read. Kudos on that classy rewrite.

My only question is where the reasonably attractive blond chick who blinks too damn much comes in.

## Here's what. (1)

## BitterOldGUy (1330491) | more than 6 years ago | (#24773143)

To what use will this long, long prime be put?

To pick up chicks!

"Hey babe! I just found the largest prime evar! Your place or mine?"

## Re:Here's what. (3, Funny)

## Anonymous Coward | more than 6 years ago | (#24773779)

"Is that a Mersenne prime in your pocket or are you just happy to see me?"

## Re:Here's what. (2, Funny)

## renegadesx (977007) | more than 6 years ago | (#24773953)

notbe new here## Re:Forgive my ignorance (2, Informative)

## OtakuPersona (1306113) | more than 6 years ago | (#24773153)

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773217)

when youbigger the prime numbers you have the harder it is to break the encryption

That sounds like a spam I got once. Does *your* dick bigger enough?

## Re:Forgive my ignorance (4, Informative)

## Brain_Recall (868040) | more than 6 years ago | (#24773227)

From the GIMPS website:

Finding new Mersenne primes is not likely to be of any immediate practical value. This search is primarily a recreational pursuit. However, the search for Mersenne primes has proved useful in development of new algorithms, testing computer hardware, and interesting young students in math.

## Re:Forgive my ignorance (5, Informative)

## Timothy Brownawell (627747) | more than 6 years ago | (#24773383)

But when it comes to primes in the 10 million digit range (I couldn't even guess how many bits you would require for a number that large)

About 33 million bits ( ln(10)/ln(2) = 3.3219 ) or 4MB.

## Re:Forgive my ignorance (1)

## wdsci (1204512) | more than 6 years ago | (#24773405)

## Re:Forgive my ignorance (4, Informative)

## Anonymous Coward | more than 6 years ago | (#24773641)

You forgot to divide by 8...bits != bytes

## Re:Forgive my ignorance (4, Insightful)

## kestasjk (933987) | more than 6 years ago | (#24773701)

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773961)

So if it's exactly 10 million digits long, then you could represent it as "10011000 10010110 10000000" (binary for ten million) with an extra 8-bit byte to signify context. A single 32-bit sequence could store any Mersenne Prime up to one with 16,777,215 digits.

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773749)

It takes about 33 million bits, and get this - each and every one of those bits is 1. Not a single zero in the lot!

## Oh hells yeah!!! (2, Funny)

## Anonymous Coward | more than 6 years ago | (#24773877)

I do IT-support in the school district...let me tell you:

...and interesting young students in math.The kids were in a veritable state of mathematics riot today.

Smoking pot, getting laid, and blowing off responsibility is so

not punk rock.God...do these guys realize how embarrassing they make adulthood?

## right (2, Funny)

## Anonymous Coward | more than 6 years ago | (#24773549)

Since this is a particularly good prime, we should

standardize on it. That way we wouldn't have to

find our own ones every time we want to use RSA.

## Re:Forgive my ignorance (3, Interesting)

## Mr.Case (1230956) | more than 6 years ago | (#24773317)

## Re:Forgive my ignorance (1)

## Timothy Brownawell (627747) | more than 6 years ago | (#24773431)

## Re:Forgive my ignorance (2, Informative)

## Matt Perry (793115) | more than 6 years ago | (#24773369)

That depends. If it's over 10,000,000 digits then it will be cashed in for $100,000 [eff.org] .

## Re:Forgive my ignorance (1)

## kestasjk (933987) | more than 6 years ago | (#24773679)

## Re:Forgive my ignorance (2, Insightful)

## Firehed (942385) | more than 6 years ago | (#24773985)

I think the real question is why it is worth $100k. I'd sure be interested to know, especially seeing that my system can probably attempt to find prime numbers pretty damn quick if it's a threaded app.

## Re:Forgive my ignorance (2, Funny)

## Anne_Nonymous (313852) | more than 6 years ago | (#24773495)

>> To what use will this long, long prime be put?

We'll sell it into slavery on the Venusian mining colonies, what else you fool?

## Re:Forgive my ignorance (4, Funny)

## RuBLed (995686) | more than 6 years ago | (#24773501)

## Re:Forgive my ignorance (1)

## renegadesx (977007) | more than 6 years ago | (#24773987)

## Re:Forgive my ignorance (4, Funny)

## zx75 (304335) | more than 6 years ago | (#24773621)

Oblg.

http://xkcd.com/435/ [xkcd.com]

## Re:Forgive my ignorance (4, Interesting)

## mochan_s (536939) | more than 6 years ago | (#24773703)

It goes towards the enormous knowledge on prime number theory.

The problem of if there is a pattern to the sequence of prime numbers is unknown. That is, if I ask you what is the 69th prime number, the only known general algorithm is to computer the 1st prime, 2nd prime and so on until the 69th prime. And, also there are unsolved problems with Mersenne primes as well.

So, if someone comes up with a good theory, then it's good to have some big examples.

And, in case you didn't know, prime number theory is used in cryptography.

## Re:Forgive my ignorance (1)

## D'Sphitz (699604) | more than 6 years ago | (#24773729)

If it's the latter i'll go download the client right now.

## Re:Forgive my ignorance (0)

## Anonymous Coward | more than 6 years ago | (#24773965)

The client, but consider that it is taking them two weeks to test this one number. It's kind of like entering the lottery, only the ticket is almost entirely free (sans electricity costs).

## Link to wikipedia would be nice (4, Informative)

## QuantumG (50515) | more than 6 years ago | (#24773059)

http://en.wikipedia.org/wiki/Mersenne_prime [wikipedia.org]

Fun.

## Re:Link to wikipedia would be nice (1)

## chubs730 (1095151) | more than 6 years ago | (#24773653)

## Well, I just beat them! (1)

## BitterOldGUy (1330491) | more than 6 years ago | (#24773063)

8-1So there!

## Re:Well, I just beat them! (2, Informative)

## Anonymous Coward | more than 6 years ago | (#24773237)

2^x -1 is never prime if x is not prime. I do believe your number falls under that category.

## Re:Well, I just beat them! (1)

## BitterOldGUy (1330491) | more than 6 years ago | (#24773255)

2^77,777,777-1 ?

## Re:Well, I just beat them! (4, Informative)

## SpottedKuh (855161) | more than 6 years ago | (#24773357)

You seem to misunderstand the meaning of prime [wikipedia.org] . Either that, or you're a horrible comedian. In either case, 77 isn't prime, and neither is 77777777.

However, even if a string of 7's were prime, that may not be enough. As stated previously, if n = 2^x - 1 is prime, then x must be prime. However, the converse is not true. That is, x being prime does not guarantee that n is prime. E.g., if x = 11, then n = 2^{11} - 1 = 2047 = 23 x 89.

## Re:Well, I just beat them! (1)

## BitterOldGUy (1330491) | more than 6 years ago | (#24773397)

Either that, or you're a horrible comedian.

So, you're saying I need to keep my day job?

## Re:Well, I just beat them! (4, Funny)

## SpottedKuh (855161) | more than 6 years ago | (#24773955)

Depends. Is your day job working as a mathematician? :)

## Re:Well, I just beat them! (0)

## Anonymous Coward | more than 6 years ago | (#24773471)

if n = 2^x - 1 is prime, then x must be prime

If that's true, can't we just solve for x and work backwards? (Since x must be prime, we would

knowwe have a prime that way) It's been awhile, but I am pretty sure you can solve for x using logorithms or something.## Re:Well, I just beat them! (0)

## Anonymous Coward | more than 6 years ago | (#24773419)

77,777,777 is not prime (divisible by 7)

## Re:Well, I just beat them! (4, Informative)

## Wardub (1264512) | more than 6 years ago | (#24773439)

## Re:Well, I just beat them! (1)

## jamesh (87723) | more than 6 years ago | (#24773689)

I think that's why he bold-ed the last digit

## The new number is (0)

## Anonymous Coward | more than 6 years ago | (#24773069)

7. No, it doesn't make any sense.

## 10 million digits (5, Funny)

## Anonymous Coward | more than 6 years ago | (#24773073)

And you only get 6 digits in prize money? What a rip off. That is only one $digit per 1.67 million prime digits.

## Re:10 million digits (1)

## philspear (1142299) | more than 6 years ago | (#24773205)

Well now, as the summary points out, it could be less than 10 million digits. For instance, it could be the previous record holder plus one. My calculator only goes up to 8 digits, so I can't test it one way or another.

## Re:10 million digits (2, Informative)

## remahl (698283) | more than 6 years ago | (#24773253)

it could be the previous record holder plus one

No, it couldn't ;-).

## Re:10 million digits (4, Funny)

## philspear (1142299) | more than 6 years ago | (#24773691)

You say that, but at some point someone told me that 1 is a prime number and 2 is as well, so therefore, prime numbers can be one prime number plus 1. Plus, I'm a biologist.

## Re:10 million digits (1)

## compro01 (777531) | more than 6 years ago | (#24773859)

A prime+1 would be divisible by 2 and therefore not prime.

## Re:10 million digits (0)

## Anonymous Coward | more than 6 years ago | (#24773307)

Your calculator doesn't do logarithms?

## Re:10 million digits (0)

## Anonymous Coward | more than 6 years ago | (#24773503)

You missed the nine million, nine hundred and ninety nine thousand, nine hundred and ninety three zeros, followed by a one after the decimal.

Don't be too hard on yourself, it's not your fault. They rounded it.

## I dont understand why this is important (0)

## Anonymous Coward | more than 6 years ago | (#24773079)

Why do we waste CPU and energy to find these?

## Re:I dont understand why this is important (5, Funny)

## philspear (1142299) | more than 6 years ago | (#24773211)

...he asks on slashdot.

## Re:I dont understand why this is important (5, Funny)

## DanWS6 (1248650) | more than 6 years ago | (#24773315)

## Because (5, Insightful)

## Bragador (1036480) | more than 6 years ago | (#24773381)

You shouldn't think like that. Just think about your question, seriously. Whatever we do is pointless and useless and everything will be destroyed eventually through the heat death of the universe.

That being said, all that is important is that you have fun doing whatever you do. Believe it or not, some people really dig maths. Also, it's one more thing the species knows.

## Re:I dont understand why this is important (4, Funny)

## gbobeck (926553) | more than 6 years ago | (#24773593)

Because doing it by hand is a real bitch and a half. Doing it by hand in moon or candle light sucks worse, I must add.

## That's *My* Prime (0, Redundant)

## Doc Ruby (173196) | more than 6 years ago | (#24773147)

Hey, *I* discovered that prime, years ago.

I just never realized it was the 45th Mersenne Prime. Thanks for filling in that gap in its resume!

## GPU's? (4, Interesting)

## EdIII (1114411) | more than 6 years ago | (#24773171)

According to their own benchmark pages a newer Core 2 Duo E8500 process in less than 21 days. Just recently I know that password cracking programs were written to use GPU's which dramatically increased the performance. Wouldn't writing code to run this on the GPU's result in even faster processing times?

## Re:GPU's? (2, Informative)

## ShadowRangerRIT (1301549) | more than 6 years ago | (#24773375)

GPU performance is geared towards floating point and massively parallel operations on small numbers. Unfortunately, neither of those characteristics are particularly handy for dealing with large primes.

Even in the general computing scenarios where they are useful, they are frequently wasting a lot of resources to accomplish the task. The Folding@Home team has noted that due to poor random access performance it is usually more efficient to recompute values than to retrieve them from memory. In practice, this means the seemingly awesome power of the GPU is often reduced by orders of magnitude relative to an equivalent ops/sec rating on a CPU.

## Re:GPU's? (4, Interesting)

## fredrikj (629833) | more than 6 years ago | (#24773579)

The Lucas-Lehmer test for Mersenne primes consists of repeated multiplication (modulo a fixed large number). Large-integer multiplication is done via floating-point FFT, which is nothing but massive amounts of operations on small numbers. I don't know how FFT implementations for GPUs compare, but intuitively I think they ought to be at least as fast as for CPUs. The primes tested by GIMPS are small enough to fit entirely in GPU memory, so latency doesn't seem like a problem.

(I don't really know much about any of this, so feel free to correct/enlighten me.)

## Re:GPU's? (0)

## Anonymous Coward | more than 6 years ago | (#24773425)

Of course. The only issue with GPU processing is the proprietary and ever-changing architectures.

You generally don't see 3 or more gpu's successively that utilize the same architecture.

GPUs are much better suited to such a task than cpus, if support were equal.

## Re:GPU's? (0)

## Anonymous Coward | more than 6 years ago | (#24773983)

The hardware in GPUs is optimized for single-precision floating point calculations, but LL testing for Mersenne primes requires double precision FP calcs, meaning that whatever advertised FLOPS for a GPU will be different than any implementation of LL testing.

There are several threads about this on mersenne forums, and the amount of work required to get it to run on a GPU client would not be worth the marginal (if any) performance gain. A GPU works a lot better for Folding@Home calculations than for LL testing. As far as my understanding goes, anyway (which is probably flawed)

## Re:GPU's? (1)

## ADBjester (1352603) | more than 6 years ago | (#24773999)

## Re:GPU's? (0)

## Anonymous Coward | more than 6 years ago | (#24774009)

According to their own benchmark pages a newer Core 2 Duo E8500 process in less than 21 days. Just recently I know that password cracking programs were written to use GPU's which dramatically increased the performance. Wouldn't writing code to run this on the GPU's result in even faster processing times?

That depends on how long it takes to write the code...

## Darn...... (1)

## B5_geek (638928) | more than 6 years ago | (#24773199)

I was hoping it would be me. I have been using ./mprime on all my boxes for years now.

Congrats to the team and world.

## Just start at infinity... (5, Funny)

## Anonymous Coward | more than 6 years ago | (#24773341)

And work backwards, that will find the largest much faster than starting at zero.

## Prediction (4, Funny)

## mrroot (543673) | more than 6 years ago | (#24773415)

## I predict that the last digit will be... (5, Funny)

## The G (7787) | more than 6 years ago | (#24773429)

...even!

## Re:I predict that the last digit will be... (4, Funny)

## Garse Janacek (554329) | more than 6 years ago | (#24773759)

...even!

Well, I guess you've got a 50% chance...

## I guess there's some room to ask... (2, Interesting)

## Anonymous Coward | more than 6 years ago | (#24773547)

... why the EFF considers it worth $100,000 of donated funds to pay someone for finding a 10,000,000-digit prime number. That is not what my donations were intended to do.

Go fix warrantless wiretapping,

thengo looking for prime numbers, kthxbye.## Re:I guess there's some room to ask... (4, Informative)

## John Miles (108215) | more than 6 years ago | (#24773585)

FTFA:

Still, it's not hard to think of some more, well, "electronic frontier-ish" applications for that kind of money. The FPGA-based DES keysearch engine they built a few years back was cool. OTOH, this Mersenne prime business just sounds like they're paying for something that will become trivial soon enough anyway.

## Re:I guess there's some room to ask... (1)

## Tacvek (948259) | more than 6 years ago | (#24773651)

Umm, that prize money was from a single donation that was made fir the precise purpose of funding this search. They are not using any other donations for this purpose. (I'm betting it was a half million dollar donation (or perhaps a full million dollar donation) made with the condition that part of it be reserved for this purpose. But the remainder of the donation would still be too large for the EFF to ignore.

## Re:I guess there's some room to ask... (0)

## Anonymous Coward | more than 6 years ago | (#24773719)

(Prize money comes from a special donation provided by an individual EFF supporter, earmarked specifically for this project. Prize money does NOT come from EFF membership dues, corporate or foundation grants, or other general EFF funds.)

## Re:I guess there's some room to ask... (1)

## appleguru (1030562) | more than 6 years ago | (#24773731)

http://www.eff.org/awards/coop [eff.org]

Most notably:

## More information please (4, Funny)

## Rob Kaper (5960) | more than 6 years ago | (#24773571)

The submitter or editor could have at least typed the number into the summary. Lazy bastards.

## Re:More information please (4, Funny)

## cheebie (459397) | more than 6 years ago | (#24773887)

They didn't because it turns out the number is 7. The math

crowd are really embarrassed that they missed it when they

were checking the first time.

"Look, no one searches for Mersenne Primes down there, because

we all know they've been found. That someone made a typo and

left out 7 went undiscovered for years. We don't like to talk

about it."

## Re:More information please (4, Funny)

## WK2 (1072560) | more than 6 years ago | (#24773893)

The number might have been too long. But they could have put the prime factorization in the summary.

## carbon impact (1)

## EmagGeek (574360) | more than 6 years ago | (#24773575)

I wonder how much electricity was used, and therefore coal and #6 burned, to find that prime - which will be used for what exactly?

## That's nothing... (0)

## Anonymous Coward | more than 6 years ago | (#24773617)

That's nothing. I found a prime number that is exactly twice as large as that one!

## Error in summary (0)

## Bradmont (513167) | more than 6 years ago | (#24773629)

I think that should read 980,000 digits, not 9.8 million (see the list at Wikipedia [wikipedia.org] ), and 1 million digit mark, not 10 million (see linked EFF page).

## Error in post (1)

## Bill, Shooter of Bul (629286) | more than 6 years ago | (#24773783)

## Re:(No) Error in summary (0)

## Anonymous Coward | more than 6 years ago | (#24773821)

I think that should read 980,000 digits, not 9.8 million (see the list at Wikipedia), and 1 million digit mark, not 10 million (see linked EFF page).

No, both Wiki and the EFF agree it's 9.8 million. The 1 million digit prize was awarded back in 2000.

The real question is what have you been smoking and where can I get some?

## Related tidbit (1)

## Normal_Deviate (807129) | more than 6 years ago | (#24773697)

I think big prime numbers are a clue. I just don't know what they are a clue to.

## Interesting (0)

## Dunbal (464142) | more than 6 years ago | (#24773747)

On slashdot, even the submitters don't RTFA apparently:

Story header: strongly suggesting that the new value may break the 10 million digit barrier

from TFA: However, the new prime

falls short of the 10 million digits required## Re:Interesting (4, Informative)

## Rob Kaper (5960) | more than 6 years ago | (#24773815)

On slashdot, even the submitters don't RTFA apparently:

Or you didn't read it properly: the bit about being just short of 10 million is about the 44th when it was new, not the new new prime.

## Depends on if you are an optimist or a pessimist (1)

## harlows_monkeys (106428) | more than 6 years ago | (#24773777)

## Moore-Otsuka-Helkenberg prime number sieve (2, Interesting)

## Jizzbug (101250) | more than 6 years ago | (#24773781)

My friends and I wrote a unique prime number sieve, using previously unknown numerological techniques (exploiting digital roots).

You can find our sieve here:

http://jessicalogsdon.com/page5/page5.html [jessicalogsdon.com]

We are currently turning our sieve in a method for rapidly factoring semi-prime numbers. Digital root mechanics have certain properties that make it easy to identify semi-prime candidacy positions in a by-9 table of the natural numbers.

A PDF at the bottom of the above-linked site explains our latest investigation of solving for [p, q] where n = p*q. The source code on the page is our prime sieve implemented in Perl.

Big Money! No Whammy! You, too, could become a hundred-millionaire M.O.H.'ing RSA to the ground!!

## Known prime found? (0)

## Anonymous Coward | more than 6 years ago | (#24773787)

I bet it'll be really exciting if one day they stumble upon a previously unknown Mersenne prime!

## So many digits... (1)

## actionbastard (1206160) | more than 6 years ago | (#24773835)