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Message boards : Number crunching : CPU + GPU, does it make a difference how much?

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Mitch
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Credit: 4,067,076
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321 LLR Bronze: Earned 10,000 credits (49,648)Cullen LLR Bronze: Earned 10,000 credits (14,932)PPS LLR Silver: Earned 100,000 credits (388,990)SR5 LLR Bronze: Earned 10,000 credits (61,092)SGS LLR Bronze: Earned 10,000 credits (30,015)TRP LLR Bronze: Earned 10,000 credits (18,581)Woodall LLR Bronze: Earned 10,000 credits (17,765)Generalized Cullen/Woodall Sieve (suspended) Silver: Earned 100,000 credits (120,136)PPS Sieve Amethyst: Earned 1,000,000 credits (1,254,012)TRP Sieve (suspended) Bronze: Earned 10,000 credits (75,329)AP 26/27 Silver: Earned 100,000 credits (121,290)GFN Amethyst: Earned 1,000,000 credits (1,915,285)
Message 71187 - Posted: 30 Nov 2013 | 6:39:20 UTC

How much CPU do you run with your GPU?? I was under the assumption that the GPU did all of the work. I played around with various settings (.250+1, .5+1, .750+1) and on all tests it still runs the CPU core at 99-100%. Is there any benefit in running more cpu into a gpu task? Or should I run at a minimum cpu and use the remainder for another cpu only WU?

Profile Gary Craig
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Discovered 1 mega prime321 LLR Ruby: Earned 2,000,000 credits (2,893,273)Cullen LLR Ruby: Earned 2,000,000 credits (2,440,687)ESP LLR Turquoise: Earned 5,000,000 credits (5,738,876)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (6,292,626)PPS LLR Turquoise: Earned 5,000,000 credits (9,648,951)PSP LLR Turquoise: Earned 5,000,000 credits (5,653,927)SoB LLR Jade: Earned 10,000,000 credits (10,558,341)SR5 LLR Turquoise: Earned 5,000,000 credits (5,748,705)SGS LLR Ruby: Earned 2,000,000 credits (3,335,713)TRP LLR Jade: Earned 10,000,000 credits (12,602,818)Woodall LLR Ruby: Earned 2,000,000 credits (2,282,622)321 Sieve Gold: Earned 500,000 credits (740,566)Cullen/Woodall Sieve (suspended) Emerald: Earned 50,000,000 credits (59,788,598)Generalized Cullen/Woodall Sieve (suspended) Ruby: Earned 2,000,000 credits (2,143,068)PPS Sieve Double Gold: Earned 500,000,000 credits (524,673,938)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Jade: Earned 10,000,000 credits (10,130,821)TRP Sieve (suspended) Jade: Earned 10,000,000 credits (10,074,710)AP 26/27 Sapphire: Earned 20,000,000 credits (43,842,888)GFN Double Silver: Earned 200,000,000 credits (224,648,943)PSA Emerald: Earned 50,000,000 credits (62,378,755)
Message 71188 - Posted: 30 Nov 2013 | 6:57:16 UTC - in response to Message 71187.

Are you referring to the "on multiprocessor systems, use at most XX % of the processors" setting, or maybe to the "use at most XX % or CPU time" settings on the Processor Usage tab of the manager's Computing Preferences? If so, it won't matter much what you set, unless (maybe) you set them very low in which case the GPU might not be used at all (not sure about that last part, though), or to 100% CPU.

The "use XX% of the processors" setting is mainly used to control how many CPU tasks run in parallel. If you set that to 100%, *and* run your GPU, then the GPU will likely slow down somewhat if there are no available cores to "feed" it as fast as if there is at least one available core. My advice would be to run some experiments on your own rig with either GFN or PPS Sieve on GPU (whichever you're interested in) and some short CPU tasks running at various %-age levels, and compare runtimes for the GPU tasks. There are too many variables to make a blanket recommendation.

--Gary

Mitch
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321 LLR Bronze: Earned 10,000 credits (49,648)Cullen LLR Bronze: Earned 10,000 credits (14,932)PPS LLR Silver: Earned 100,000 credits (388,990)SR5 LLR Bronze: Earned 10,000 credits (61,092)SGS LLR Bronze: Earned 10,000 credits (30,015)TRP LLR Bronze: Earned 10,000 credits (18,581)Woodall LLR Bronze: Earned 10,000 credits (17,765)Generalized Cullen/Woodall Sieve (suspended) Silver: Earned 100,000 credits (120,136)PPS Sieve Amethyst: Earned 1,000,000 credits (1,254,012)TRP Sieve (suspended) Bronze: Earned 10,000 credits (75,329)AP 26/27 Silver: Earned 100,000 credits (121,290)GFN Amethyst: Earned 1,000,000 credits (1,915,285)
Message 71190 - Posted: 30 Nov 2013 | 7:23:37 UTC - in response to Message 71188.

I was referring to app_config.xml and the ability to set processor usage tied to the GPU. I don't remember the default setting, but it was running something along the line of .187 cpu + 1 gpu. When I added my second card it would run two tasks with .187 cpu + 1 gpu, but it doesn't say which task is running on the remaining .7xx cpu. I changed my app_config to run .5 cpu to each gpu. I was just interested in how much of a difference it makes. Like if I was to run 1 full core to each GPU would it speed things up noticeably? I'm running Genefer and haven't had the enough tasks complete to get the full picture, thought maybe someone had some experience with this.

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Found 2 primes in the 2018 Tour de PrimesFound 1 prime in the 2020 Tour de Primes321 LLR Turquoise: Earned 5,000,000 credits (6,042,688)Cullen LLR Turquoise: Earned 5,000,000 credits (5,101,836)ESP LLR Turquoise: Earned 5,000,000 credits (5,303,526)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (5,202,873)PPS LLR Turquoise: Earned 5,000,000 credits (6,098,851)PSP LLR Turquoise: Earned 5,000,000 credits (5,513,728)SoB LLR Turquoise: Earned 5,000,000 credits (8,851,996)SR5 LLR Turquoise: Earned 5,000,000 credits (5,199,189)SGS LLR Turquoise: Earned 5,000,000 credits (5,100,018)TRP LLR Turquoise: Earned 5,000,000 credits (5,405,027)Woodall LLR Turquoise: Earned 5,000,000 credits (5,124,820)321 Sieve Jade: Earned 10,000,000 credits (10,003,334)Cullen/Woodall Sieve (suspended) Silver: Earned 100,000 credits (268,250)Generalized Cullen/Woodall Sieve (suspended) Jade: Earned 10,000,000 credits (10,000,502)PPS Sieve Double Silver: Earned 200,000,000 credits (306,761,000)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Jade: Earned 10,000,000 credits (10,000,133)TRP Sieve (suspended) Jade: Earned 10,000,000 credits (10,000,970)AP 26/27 Double Bronze: Earned 100,000,000 credits (190,526,375)GFN Double Bronze: Earned 100,000,000 credits (133,333,389)PSA Double Silver: Earned 200,000,000 credits (200,000,001)
Message 71191 - Posted: 30 Nov 2013 | 8:38:44 UTC

Setting the xx% of CPU time is effectively heat-cycling your CPU which will kill it.

Profile Michael GoetzProject donor
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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 Primes321 LLR Ruby: Earned 2,000,000 credits (2,822,730)Cullen LLR Ruby: Earned 2,000,000 credits (2,005,249)ESP LLR Turquoise: Earned 5,000,000 credits (5,009,577)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,145,754)PPS LLR Jade: Earned 10,000,000 credits (15,524,174)PSP LLR Turquoise: Earned 5,000,000 credits (5,197,957)SoB LLR Sapphire: Earned 20,000,000 credits (34,291,181)SR5 LLR Jade: Earned 10,000,000 credits (10,007,110)SGS LLR Ruby: Earned 2,000,000 credits (2,276,330)TRP LLR Turquoise: Earned 5,000,000 credits (5,084,329)Woodall LLR Ruby: Earned 2,000,000 credits (2,195,123)321 Sieve 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 (10,118,303)GFN Emerald: Earned 50,000,000 credits (74,619,459)PSA Jade: Earned 10,000,000 credits (12,445,029)
Message 71193 - Posted: 30 Nov 2013 | 11:59:02 UTC

That setting (in app_info) does not do what you think it does. You probably shouldn't touch it.

It is not possible to "set" the CPU/GPU ratio. The computer uses as much CPU as is necessary to keep the GPU busy. This is always true, and you have no direct control over that.

In fact, even the number that you see for CPU/GPU usage in the BOINC manager is completely bogus. BOINC is not measuring how much CPU is being used. What you see there is a complete guess, based on several estimated numbers. The end result (what you see) is pretty worthless. If you want a good idea of how much CPU is actually being used, you need to look in task manager (Windows), or the equivalent under Linux or OSX.

What the setting doesn't do is tell BOINC how much CPU it should use. Instead, it tells BOINC how much you EXPECT the CPU to use. If the sum of the estimated CPU "percentage" on all running GPU jobs exceeds 1.00, then BOINC will reserve a CPU core just for running the GPU jobs and won't run a CPU task on that core. If the sum is less than 1.00, then it won't reserve a core for servicing the GPUs and will run CPU tasks on all cores. If the sum is greater than 2.00, it will reserve two CPU cores for servicing the GPUs, etc.
____________
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Discovered 1 mega prime321 LLR Ruby: Earned 2,000,000 credits (2,038,739)Cullen LLR Ruby: Earned 2,000,000 credits (2,074,615)ESP LLR Ruby: Earned 2,000,000 credits (2,013,823)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,142,353)PPS LLR Turquoise: Earned 5,000,000 credits (5,149,318)PSP LLR Ruby: Earned 2,000,000 credits (2,049,284)SoB LLR Amethyst: Earned 1,000,000 credits (1,043,824)SR5 LLR Ruby: Earned 2,000,000 credits (2,053,250)SGS LLR Turquoise: Earned 5,000,000 credits (5,095,282)TRP LLR Ruby: Earned 2,000,000 credits (2,025,737)Woodall LLR Amethyst: Earned 1,000,000 credits (1,812,281)321 Sieve Sapphire: Earned 20,000,000 credits (23,770,672)Cullen/Woodall Sieve (suspended) Gold: Earned 500,000 credits (944,431)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,813,253)PPS Sieve Double Silver: Earned 200,000,000 credits (339,648,557)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Ruby: Earned 2,000,000 credits (2,446,797)AP 26/27 Sapphire: Earned 20,000,000 credits (33,140,471)GFN Sapphire: Earned 20,000,000 credits (36,461,143)PSA Sapphire: Earned 20,000,000 credits (20,457,430)
Message 71195 - Posted: 30 Nov 2013 | 13:06:06 UTC - in response to Message 71190.

I was referring to app_config.xml and the ability to set processor usage tied to the GPU. I don't remember the default setting, but it was running something along the line of .187 cpu + 1 gpu. When I added my second card it would run two tasks with .187 cpu + 1 gpu, but it doesn't say which task is running on the remaining .7xx cpu. I changed my app_config to run .5 cpu to each gpu. I was just interested in how much of a difference it makes. Like if I was to run 1 full core to each GPU would it speed things up noticeably? I'm running Genefer and haven't had the enough tasks complete to get the full picture, thought maybe someone had some experience with this.


I think those settings give a MAXIMUM to use not the actual amount to use, meaning using those settings tells to the pc to use anything UPTO that amount but no more, NOT to use exactly that amount. The actual amount used is determined by the project and how they made the actual units we are crunching. It also depends on whether you are using an AMD or Nvidia gpu as each of their software profiles are different. And of course each version of the gpu's software changes things too, the 3 latest Nvidia versions actually slowed down crunching, but sped up the gaming stuff.

As for leaving a cpu core free the general rule of thumb is to yes do it, but that is only a generalization not a hard and fast rule. A gpu can give 10 times the credits, and do 10 times the work in the process, that a cpu core can, so leaving a cpu core free makes sense. But some work units on some gpu's only use below 0.2% of a cpu core, leaving the cpu core idle most of the time. In those instances it is normal to also crunch using all the cpu cores as you really are losing that much. But each project and even sub project within the overall project is different and needs to be thought of on a stand alone basis. Meaning what works for one may not work for another, as well as an AMD gpu may only use only 0.2% of a cpu core while an Nvidia gpu might use 0.784% of a cpu core running the same sub project.

Crunching with a gpu is not a set and forget kind of thing unless you are using the defaults and then it just works. But if you start tweaking, like alot of us do, it can get real complicated real quick.

Profile Michael GoetzProject donor
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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 Primes321 LLR Ruby: Earned 2,000,000 credits (2,822,730)Cullen LLR Ruby: Earned 2,000,000 credits (2,005,249)ESP LLR Turquoise: Earned 5,000,000 credits (5,009,577)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,145,754)PPS LLR Jade: Earned 10,000,000 credits (15,524,174)PSP LLR Turquoise: Earned 5,000,000 credits (5,197,957)SoB LLR Sapphire: Earned 20,000,000 credits (34,291,181)SR5 LLR Jade: Earned 10,000,000 credits (10,007,110)SGS LLR Ruby: Earned 2,000,000 credits (2,276,330)TRP LLR Turquoise: Earned 5,000,000 credits (5,084,329)Woodall LLR Ruby: Earned 2,000,000 credits (2,195,123)321 Sieve 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 (10,118,303)GFN Emerald: Earned 50,000,000 credits (74,619,459)PSA Jade: Earned 10,000,000 credits (12,445,029)
Message 71196 - Posted: 30 Nov 2013 | 13:37:06 UTC - in response to Message 71195.

I was referring to app_config.xml ...


I think those settings give a MAXIMUM to use not the actual amount to use...


In the post before yours, I explained what that setting does. It doesn't set anything; it merely tells BOINC how much you expect it to use. Unless you're trying to force BOINC to leave a core free to service the GPU, or to stop it from doing that, there's no reason to use that setting in app_info.
____________
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Discovered 1 mega prime321 LLR Ruby: Earned 2,000,000 credits (2,038,739)Cullen LLR Ruby: Earned 2,000,000 credits (2,074,615)ESP LLR Ruby: Earned 2,000,000 credits (2,013,823)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,142,353)PPS LLR Turquoise: Earned 5,000,000 credits (5,149,318)PSP LLR Ruby: Earned 2,000,000 credits (2,049,284)SoB LLR Amethyst: Earned 1,000,000 credits (1,043,824)SR5 LLR Ruby: Earned 2,000,000 credits (2,053,250)SGS LLR Turquoise: Earned 5,000,000 credits (5,095,282)TRP LLR Ruby: Earned 2,000,000 credits (2,025,737)Woodall LLR Amethyst: Earned 1,000,000 credits (1,812,281)321 Sieve Sapphire: Earned 20,000,000 credits (23,770,672)Cullen/Woodall Sieve (suspended) Gold: Earned 500,000 credits (944,431)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,813,253)PPS Sieve Double Silver: Earned 200,000,000 credits (339,648,557)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Ruby: Earned 2,000,000 credits (2,446,797)AP 26/27 Sapphire: Earned 20,000,000 credits (33,140,471)GFN Sapphire: Earned 20,000,000 credits (36,461,143)PSA Sapphire: Earned 20,000,000 credits (20,457,430)
Message 71208 - Posted: 1 Dec 2013 | 12:31:48 UTC - in response to Message 71196.

I was referring to app_config.xml ...


I think those settings give a MAXIMUM to use not the actual amount to use...


In the post before yours, I explained what that setting does. It doesn't set anything; it merely tells BOINC how much you expect it to use. Unless you're trying to force BOINC to leave a core free to service the GPU, or to stop it from doing that, there's no reason to use that setting in app_info.


I see that now, sorry I skimmed it and missed what you were saying!

Message boards : Number crunching : CPU + GPU, does it make a difference how much?

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