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Message boards : Number crunching : sli/crossfire

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Message 34243 - Posted: 17 Mar 2011 | 22:58:31 UTC

Does primegrid take advantage of sli/crossfire?

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Message 34254 - Posted: 18 Mar 2011 | 13:56:31 UTC - in response to Message 34243.

No.
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The "Shut up already!" badge:  This loud mouth has mansplained on the forums over 10 thousand times!  Sheesh!!!Discovered the World's First GFN-19 prime!!!Discovered 1 mega primeFound 1 prime in the 2018 Tour de PrimesFound 1 prime in the 2019 Tour de PrimesFound 1 prime in the 2020 Tour de PrimesFound 2 primes in the 2021 Tour de Primes321 LLR Turquoise: Earned 5,000,000 credits (5,132,712)Cullen LLR Turquoise: Earned 5,000,000 credits (5,038,114)ESP LLR Turquoise: Earned 5,000,000 credits (6,177,890)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (5,094,541)PPS LLR Sapphire: Earned 20,000,000 credits (20,817,335)PSP LLR Turquoise: Earned 5,000,000 credits (7,956,186)SoB LLR Sapphire: Earned 20,000,000 credits (36,067,618)SR5 LLR Jade: Earned 10,000,000 credits (10,007,110)SGS LLR Ruby: Earned 2,000,000 credits (4,470,298)TRP LLR Turquoise: Earned 5,000,000 credits (5,084,329)Woodall LLR Turquoise: Earned 5,000,000 credits (5,032,821)321 Sieve (suspended) Jade: Earned 10,000,000 credits (10,061,196)Cullen/Woodall Sieve (suspended) Ruby: Earned 2,000,000 credits (4,170,256)Generalized Cullen/Woodall Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,059,304)PPS Sieve Sapphire: Earned 20,000,000 credits (22,885,121)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Amethyst: Earned 1,000,000 credits (1,035,522)TRP Sieve (suspended) Ruby: Earned 2,000,000 credits (2,051,121)AP 26/27 Jade: Earned 10,000,000 credits (10,902,645)GFN Emerald: Earned 50,000,000 credits (89,400,820)WW Emerald: Earned 50,000,000 credits (50,024,000)PSA Jade: Earned 10,000,000 credits (12,445,029)
Message 34261 - Posted: 18 Mar 2011 | 15:12:31 UTC - in response to Message 34243.

I'm pretty sure CUDA itself can't take advantage of SLI, so there's no way to use two nVidia cards under SLI. As I remember it, if you turn on SLI, the video cards are not usable by CUDA. At least that used to be the case. It's possible this has changed, but I doubt it.

Not sure about ATI, but I suspect the same holds true for Crossfire.

So it's not really a question of whether PrimeGrid can take advantage of SLI/XFire; I'm pretty sure no GPU computing project of any sort, BOINC or not, can use them.

Then again, I'm not sure why you would ever want to. SLI/XFire is a method for combining multiple GPUs to drive a single video screen.

For generalized computing problems, you don't need the ability to have multiple controllers manipulating the same screen (which is the purpose of SLI/XFire). If you want to use multiple GPUs for a computing problem, you simply write the application to use multiple GPUs. You don't need SLI or XFire to do that. It's analogous to using multiple CPU cores:

Most BOINC applications, including all those here at PrimeGrid, only use a single core. Multiple cores are utilized by running multiple WUs in parallel. A very small number of applications are specifically designed to use multiple cores (e.g., Aqua@home). Likewise, nearly all GPU apps currently can only use a single GPU, although it's theoretically possible to create an app that uses multiple GPUs.

For PrimeGrid, there's absolutely no reason to have a multi-GPU application, because the existing GPU-capable apps runs pretty quickly right now. If a GPU app takes 4 minutes to run on a GPU and you have two GPUs, it doesn't make much difference if you run one app on each gpu in parallel (taking four minutes), or two apps, one after the other utilizing both GPUs, with each app taking 2 minutes. By contrast, GPUGRID has fairly lengthy WUs, and a case could be made for them creating an application that utilizes multiple GPUs. PrimeGrid, however, wouldn't benefit from such an application.

Finally, to reiterate, the literal answer to your question is a simple "no". SLI and Crossfire aren't used for general purpose GPU computing, only for video display processing.
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Message 34281 - Posted: 18 Mar 2011 | 20:46:11 UTC - in response to Message 34261.
Last modified: 18 Mar 2011 | 20:53:57 UTC

It's analogous to using multiple CPU cores:

Most BOINC applications, including all those here at PrimeGrid, only use a single core. Multiple cores are utilized by running multiple WUs in parallel. A very small number of applications are specifically designed to use multiple cores (e.g., Aqua@home). Likewise, nearly all GPU apps currently can only use a single GPU, although it's theoretically possible to create an app that uses multiple GPUs.

For PrimeGrid, there's absolutely no reason to have a multi-GPU application, because the existing GPU-capable apps runs pretty quickly right now. If a GPU app takes 4 minutes to run on a GPU and you have two GPUs, it doesn't make much difference if you run one app on each gpu in parallel (taking four minutes), or two apps, one after the other utilizing both GPUs, with each app taking 2 minutes. By contrast, GPUGRID has fairly lengthy WUs, and a case could be made for them creating an application that utilizes multiple GPUs. PrimeGrid, however, wouldn't benefit from such an application

Actually the reason of multi-GPU application for PrimeGrid GPU projects exists.
If, for axample, one 9600GT needs ~6700 sec for PPS Sieve (cuda23), during 1 day challenge 2 9600GT's separately can do 12 WUs everyone. But 2 GPUs commonly will overdue 25 WUs. 25/24 = ~1.042 = 4.2%
I understand that for fast GPUs this difference aspires to 0
But from the perspective of 1) llrcuda and 2) resolving the problem of defining of Initial Finder of prime, the reason of the faster multi-GPU and multi-cores (CPU) applications exists.

BTW, DNETC@Home able to use several GPUs for 1 WU.

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Message 34282 - Posted: 18 Mar 2011 | 21:36:36 UTC - in response to Message 34281.

...the reason of the faster multi-GPU and multi-cores (CPU) applications exists.

If you or anyone can provide a "multi-GPU or multi-core (CPU) application" for primality testing candidates in PrimeGrid's current projects, we'll gladly implement it. ;) It's always refreshing to ask for the seemingly impossible. :D
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Message 34284 - Posted: 18 Mar 2011 | 21:59:20 UTC - in response to Message 34282.
Last modified: 18 Mar 2011 | 22:00:04 UTC

...the reason of the faster multi-GPU and multi-cores (CPU) applications exists.

If you or anyone can provide a "multi-GPU or multi-core (CPU) application" for primality testing candidates in PrimeGrid's current projects, we'll gladly implement it. ;) It's always refreshing to ask for the seemingly impossible. :D


I suspect it's a lot easier than you think. Whether there's any value in doing so is another question.

If you've got an application that already runs on a single GPU, you're already splitting the work up into little pieces. Create multiple threads (or possibly multiple processes; it depends on how the CUDA libraries like talking to multiple GPUs) with each thread talking to one of the GPUs.

The hard part is getting ONE GPU to work. Once you've figured out how to parallelize the application, getting more than one GPU to work should just be a matter of beating the library code into submission.
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Message 34285 - Posted: 18 Mar 2011 | 22:24:13 UTC - in response to Message 34284.

Nowadays (at least for a year), you can choose to have SLI/CF enabled and BOINC will still see multiple separate GPUs. So if you have 2 GPUs, BOINC will run one task on each of them.

I run all of my setups this way, since it eliminates the sometimes needed dummy plug in a card not connected to a monitor.

DNETC can run one job on several GPUs, but in reality it only starts 2 threads in the same job. This could easily be done with sieves as well, but it has no real benefit. You simply run 2 tasks in parallel instead.

Some tasks are very linear (e g LLR) and are not easily threadable. This is because the calculations made, depend on the previous calculation. Usually you need to modify the present algorithm or invent a new one to make the calculation more threadable.

Also if you use multiple threads you might lose performance (i e the added threads might not give 100% speed per thread). In this case it becomes a choice between throughput (total work done) and latency (time for each task to complete).

/Snf


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Message 34606 - Posted: 29 Mar 2011 | 21:45:02 UTC

hi,

i'm new to this project but have been running twin two core 5970's on milkyway quite happily x-fired and crunching 4 work units seperatly so its more than possible

plus if you look at the top computers on this site pages there are lots of people who are using two seperate gpu's to crunch some achieving credits of well over a million
so i'm not sure whether you mean using these cards completely seperately ?
but if thats true or that they just dont work in x-fire?
will that mean that the new nvidia 590 will never work on this project because of having twin cores onboard ?

best regards
Ian

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Discovered the World's First base 116 Generalized Cullen prime!!!Discovered 37 mega primesEliminated 7 conjecture "k"sDiscovered 1 Sophie Germain pairDiscovered 2 Fermat divisors2012 Tour de Primes highest prime count2012 Tour de Primes most Mountain Stage primes2015 Tour de Primes highest prime count2016 Tour de Primes highest prime countFound 23 primes in the 2018 Tour de PrimesFound 1 mega prime in the 2018 Tour de PrimesFound 2 primes in the 2018 Tour de Primes Mountain Stage2019 Tour de Primes highest prime countFound 22 primes in the 2019 Tour de Primes2020 Tour de Primes highest prime scoreFound 21 primes in the 2020 Tour de PrimesFound 4 mega primes in the 2020 Tour de PrimesFound 8 primes in the 2021 Tour de PrimesFound 1 mega prime in the 2021 Tour de Primes321 LLR Double Silver: Earned 200,000,000 credits (201,403,028)Cullen LLR Double Silver: Earned 200,000,000 credits (201,409,561)ESP LLR Double Silver: Earned 200,000,000 credits (214,825,147)Generalized Cullen/Woodall LLR Double Silver: Earned 200,000,000 credits (201,112,468)PPS LLR Double Gold: Earned 500,000,000 credits (810,437,155)PSP LLR Double Silver: Earned 200,000,000 credits (201,749,918)SoB LLR Double Silver: Earned 200,000,000 credits (207,028,068)SR5 LLR Double Silver: Earned 200,000,000 credits (214,437,634)SGS LLR Double Silver: Earned 200,000,000 credits (205,718,935)TPS LLR (retired) Silver: Earned 100,000 credits (235,439)TRP LLR Double Silver: Earned 200,000,000 credits (201,215,056)Woodall LLR Double Silver: Earned 200,000,000 credits (201,651,344)321 Sieve (suspended) Double Silver: Earned 200,000,000 credits (235,451,253)Cullen/Woodall Sieve (suspended) Emerald: Earned 50,000,000 credits (83,794,448)Generalized Cullen/Woodall Sieve (suspended) Double Silver: Earned 200,000,000 credits (285,139,652)PPS Sieve Double Ruby: Earned 2,000,000,000 credits (2,736,221,354)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Double Silver: Earned 200,000,000 credits (203,523,358)TRP Sieve (suspended) Double Silver: Earned 200,000,000 credits (201,489,157)AP 26/27 Double Gold: Earned 500,000,000 credits (512,586,204)GFN Double Ruby: Earned 2,000,000,000 credits (2,269,843,802)WW Double Ruby: Earned 2,000,000,000 credits (3,476,036,000)PSA Double Silver: Earned 200,000,000 credits (259,058,048)
Message 34608 - Posted: 29 Mar 2011 | 22:13:06 UTC - in response to Message 34606.

hi,

i'm new to this project but have been running twin two core 5970's on milkyway quite happily x-fired and crunching 4 work units seperatly so its more than possible

plus if you look at the top computers on this site pages there are lots of people who are using two seperate gpu's to crunch some achieving credits of well over a million
so i'm not sure whether you mean using these cards completely seperately ?
but if thats true or that they just dont work in x-fire?
will that mean that the new nvidia 590 will never work on this project because of having twin cores onboard ?

best regards
Ian


The twin-GPU issue is unique to the ATI cards here at PG due to issues with the OpenCL drivers. NVidia cards run a CUDA application rather than OpenCL, and thus, should not experience the same issues.


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Message boards : Number crunching : sli/crossfire

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