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Message boards : Number crunching : Is turning on hyper threading better if you still assign number of tasks to only pysical cores?

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Profile Jordan Romaidis
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Discovered 4 mega primesEliminated 1 conjecture "k"Discovered 1 AP26Found 1 prime in the 2018 Tour de PrimesFound 2 primes in the 2019 Tour de PrimesFound 2 primes in the 2020 Tour de PrimesFound 1 mega prime in the 2020 Tour de PrimesFound 1 prime in the 2020 Tour de Primes Mountain StageFound 1 mega prime in the 2020 Tour de Primes Mountain Stage321 LLR Turquoise: Earned 5,000,000 credits (5,014,730)Cullen LLR Ruby: Earned 2,000,000 credits (2,080,460)ESP LLR Gold: Earned 500,000 credits (502,325)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (6,000,054)PPS LLR Emerald: Earned 50,000,000 credits (95,748,889)PSP LLR Silver: Earned 100,000 credits (168,701)SoB LLR Sapphire: Earned 20,000,000 credits (39,985,666)SR5 LLR Jade: Earned 10,000,000 credits (16,535,456)SGS LLR Jade: Earned 10,000,000 credits (18,577,642)TRP LLR Gold: Earned 500,000 credits (525,711)Woodall LLR Jade: Earned 10,000,000 credits (15,028,246)321 Sieve Amethyst: Earned 1,000,000 credits (1,084,376)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,606,749)PPS Sieve Sapphire: Earned 20,000,000 credits (23,323,949)AP 26/27 Double Silver: Earned 200,000,000 credits (232,452,285)GFN Double Bronze: Earned 100,000,000 credits (146,257,211)PSA Emerald: Earned 50,000,000 credits (52,891,089)
Message 147188 - Posted: 31 Dec 2020 | 1:40:48 UTC

All things being equal, if I assign a number of tasks only to the number of physical cores but turn on hyper threading for any kind of "overhead" would you generally expect better performance?

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Discovered 1 mega primeFound 4 primes in the 2019 Tour de PrimesFound 1 prime in the 2020 Tour de Primes321 LLR Turquoise: Earned 5,000,000 credits (5,669,908)Cullen LLR Turquoise: Earned 5,000,000 credits (5,139,658)ESP LLR Ruby: Earned 2,000,000 credits (4,143,966)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,072,438)PPS LLR Jade: Earned 10,000,000 credits (14,101,227)PSP LLR Turquoise: Earned 5,000,000 credits (6,178,082)SoB LLR Turquoise: Earned 5,000,000 credits (5,469,275)SR5 LLR Turquoise: Earned 5,000,000 credits (8,815,713)SGS LLR Turquoise: Earned 5,000,000 credits (5,290,581)TRP LLR Turquoise: Earned 5,000,000 credits (5,854,419)Woodall LLR Turquoise: Earned 5,000,000 credits (6,340,642)321 Sieve Sapphire: Earned 20,000,000 credits (26,182,363)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (29,540,183)PPS Sieve Double Bronze: Earned 100,000,000 credits (111,482,341)AP 26/27 Sapphire: Earned 20,000,000 credits (26,655,499)GFN Double Bronze: Earned 100,000,000 credits (141,666,475)PSA Double Bronze: Earned 100,000,000 credits (111,434,026)
Message 147189 - Posted: 31 Dec 2020 | 2:32:30 UTC - in response to Message 147188.

These things vary from system to system, from OS to OS, and from subproject to subprojects; only way to know for sure is to try it out for yourself.

That being said, there typically isn't that great of a difference IIRC.

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Discovered 4 mega primesEliminated 1 conjecture "k"Discovered 1 AP26Found 1 prime in the 2018 Tour de PrimesFound 2 primes in the 2019 Tour de PrimesFound 2 primes in the 2020 Tour de PrimesFound 1 mega prime in the 2020 Tour de PrimesFound 1 prime in the 2020 Tour de Primes Mountain StageFound 1 mega prime in the 2020 Tour de Primes Mountain Stage321 LLR Turquoise: Earned 5,000,000 credits (5,014,730)Cullen LLR Ruby: Earned 2,000,000 credits (2,080,460)ESP LLR Gold: Earned 500,000 credits (502,325)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (6,000,054)PPS LLR Emerald: Earned 50,000,000 credits (95,748,889)PSP LLR Silver: Earned 100,000 credits (168,701)SoB LLR Sapphire: Earned 20,000,000 credits (39,985,666)SR5 LLR Jade: Earned 10,000,000 credits (16,535,456)SGS LLR Jade: Earned 10,000,000 credits (18,577,642)TRP LLR Gold: Earned 500,000 credits (525,711)Woodall LLR Jade: Earned 10,000,000 credits (15,028,246)321 Sieve Amethyst: Earned 1,000,000 credits (1,084,376)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,606,749)PPS Sieve Sapphire: Earned 20,000,000 credits (23,323,949)AP 26/27 Double Silver: Earned 200,000,000 credits (232,452,285)GFN Double Bronze: Earned 100,000,000 credits (146,257,211)PSA Emerald: Earned 50,000,000 credits (52,891,089)
Message 147192 - Posted: 31 Dec 2020 | 3:21:26 UTC - in response to Message 147189.

Thanks James!

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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 Jade: Earned 10,000,000 credits (10,011,570)Cullen LLR Jade: Earned 10,000,000 credits (10,009,374)ESP LLR Jade: Earned 10,000,000 credits (10,009,221)Generalized Cullen/Woodall LLR Jade: Earned 10,000,000 credits (10,012,217)PPS LLR Jade: Earned 10,000,000 credits (11,055,307)PSP LLR Jade: Earned 10,000,000 credits (10,044,081)SoB LLR Jade: Earned 10,000,000 credits (10,064,750)SR5 LLR Jade: Earned 10,000,000 credits (10,002,051)SGS LLR Jade: Earned 10,000,000 credits (10,001,215)TRP LLR Jade: Earned 10,000,000 credits (10,002,411)Woodall LLR Jade: Earned 10,000,000 credits (10,013,921)321 Sieve Sapphire: Earned 20,000,000 credits (20,004,228)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,047,667)PPS Sieve Sapphire: Earned 20,000,000 credits (20,866,490)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,043,271)TRP Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,015,177)AP 26/27 Sapphire: Earned 20,000,000 credits (20,045,194)GFN Emerald: Earned 50,000,000 credits (53,545,357)PSA Double Silver: Earned 200,000,000 credits (200,301,443)
Message 147200 - Posted: 31 Dec 2020 | 7:25:16 UTC - in response to Message 147188.

All things being equal, if I assign a number of tasks only to the number of physical cores but turn on hyper threading for any kind of "overhead" would you generally expect better performance?

It depends on how OS kernel works. Not sure about better performance, but, at least, it does not harm much under Linux - Linux kernel is smart enough to correctly schedule tasks on different physical cores. You may quickly change run mode at will (using real cores only for LLR or all cores for sieving) without need to reboot and go to BIOS to turn HT on/off.

Windows is completely different story. I'm not sure about Windows 10, but early it did not distinguished between real and virtual/hyperthreaded cores, so you may end up running things on half of your real cores in hyperthreaded mode. I think that under Windows you must pin applications (or Boinc.exe itself, so started applications will inherit this setting) to correct set of "real" processor cores.

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Discovered 4 mega primesEliminated 1 conjecture "k"Found 3 primes in the 2018 Tour de PrimesFound 1 mega prime in the 2018 Tour de PrimesFound 5 primes in the 2019 Tour de PrimesFound 6 primes in the 2020 Tour de Primes321 LLR Turquoise: Earned 5,000,000 credits (8,774,878)Cullen LLR Turquoise: Earned 5,000,000 credits (5,903,451)ESP LLR Turquoise: Earned 5,000,000 credits (6,454,573)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (5,122,074)PPS LLR Emerald: Earned 50,000,000 credits (83,377,417)PSP LLR Jade: Earned 10,000,000 credits (15,223,714)SoB LLR Jade: Earned 10,000,000 credits (17,319,914)SR5 LLR Sapphire: Earned 20,000,000 credits (23,996,561)SGS LLR Turquoise: Earned 5,000,000 credits (7,342,780)TPS LLR (retired) Bronze: Earned 10,000 credits (34,130)TRP LLR Jade: Earned 10,000,000 credits (19,866,589)Woodall LLR Turquoise: Earned 5,000,000 credits (8,171,820)321 Sieve Sapphire: Earned 20,000,000 credits (20,236,219)Cullen/Woodall Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,383,853)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,626,419)PPS Sieve Emerald: Earned 50,000,000 credits (76,969,144)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Ruby: Earned 2,000,000 credits (2,293,882)TRP Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,012,757)AP 26/27 Sapphire: Earned 20,000,000 credits (21,918,894)GFN Emerald: Earned 50,000,000 credits (76,466,089)PSA Ruby: Earned 2,000,000 credits (2,939,755)
Message 147202 - Posted: 31 Dec 2020 | 10:02:42 UTC

My observations on Windows:

If you run single thread LLR tasks, one per core, HT on is ~10% worse than HT off. Windows scheduler is doing something bad here, which I nicknames "core smear" as it moves the threads around and I think it overlaps them at times, hence the performance loss. Can be worked around by manually setting affinity to the boinc process, which gets inherited by tasks it runs subsequently.

If you run multi-thread LLR tasks, one thread per core, HT on is essentially no different than HT off. Something about the MT operation means Windows is less stupid.

If the system is a pure cruncher, turning off HT makes things easier to manage. I don't normally run GPU tasks at the same time so don't know how that changes things.

If you run multi-socket NUMA systems with Windows, I'd go HT off unless you like micro-managing where the tasks end up.

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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 (5,225,319)PSP LLR Ruby: Earned 2,000,000 credits (2,049,284)SoB LLR Ruby: Earned 2,000,000 credits (2,700,268)SR5 LLR Ruby: Earned 2,000,000 credits (2,053,250)SGS LLR Turquoise: Earned 5,000,000 credits (5,147,768)TRP LLR Ruby: Earned 2,000,000 credits (2,025,737)Woodall LLR Ruby: Earned 2,000,000 credits (2,014,811)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 (339,665,412)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 (41,983,025)PSA Sapphire: Earned 20,000,000 credits (20,457,430)
Message 147206 - Posted: 31 Dec 2020 | 12:01:48 UTC - in response to Message 147202.

My observations on Windows:

If you run single thread LLR tasks, one per core, HT on is ~10% worse than HT off. Windows scheduler is doing something bad here, which I nicknames "core smear" as it moves the threads around and I think it overlaps them at times, hence the performance loss. Can be worked around by manually setting affinity to the boinc process, which gets inherited by tasks it runs subsequently.


Does the program Project Lasso assist in keeping them on the real cpu cores and away from the HT ones?

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321 LLR Turquoise: Earned 5,000,000 credits (7,879,763)Cullen LLR Turquoise: Earned 5,000,000 credits (6,828,213)ESP LLR Turquoise: Earned 5,000,000 credits (5,055,512)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (6,457,215)PPS LLR Turquoise: Earned 5,000,000 credits (8,645,607)PSP LLR Turquoise: Earned 5,000,000 credits (6,104,395)SoB LLR Jade: Earned 10,000,000 credits (10,245,712)SR5 LLR Turquoise: Earned 5,000,000 credits (6,730,319)SGS LLR Turquoise: Earned 5,000,000 credits (5,334,462)TRP LLR Jade: Earned 10,000,000 credits (10,009,531)Woodall LLR Turquoise: Earned 5,000,000 credits (6,638,546)321 Sieve Sapphire: Earned 20,000,000 credits (20,019,388)Cullen/Woodall Sieve (suspended) Double Silver: Earned 200,000,000 credits (265,102,350)PPS Sieve Double Gold: Earned 500,000,000 credits (546,715,203)TRP Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,801,812)AP 26/27 Emerald: Earned 50,000,000 credits (61,259,536)GFN Double Silver: Earned 200,000,000 credits (249,675,265)
Message 147209 - Posted: 31 Dec 2020 | 13:54:52 UTC - in response to Message 147206.

My observations on Windows:

If you run single thread LLR tasks, one per core, HT on is ~10% worse than HT off. Windows scheduler is doing something bad here, which I nicknames "core smear" as it moves the threads around and I think it overlaps them at times, hence the performance loss. Can be worked around by manually setting affinity to the boinc process, which gets inherited by tasks it runs subsequently.


Does the program Project Lasso assist in keeping them on the real cpu cores and away from the HT ones?

As I understand it they're the same - with HT on each physical core has 2 virtual cores.

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Discovered 4 mega primesEliminated 1 conjecture "k"Found 3 primes in the 2018 Tour de PrimesFound 1 mega prime in the 2018 Tour de PrimesFound 5 primes in the 2019 Tour de PrimesFound 6 primes in the 2020 Tour de Primes321 LLR Turquoise: Earned 5,000,000 credits (8,774,878)Cullen LLR Turquoise: Earned 5,000,000 credits (5,903,451)ESP LLR Turquoise: Earned 5,000,000 credits (6,454,573)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (5,122,074)PPS LLR Emerald: Earned 50,000,000 credits (83,377,417)PSP LLR Jade: Earned 10,000,000 credits (15,223,714)SoB LLR Jade: Earned 10,000,000 credits (17,319,914)SR5 LLR Sapphire: Earned 20,000,000 credits (23,996,561)SGS LLR Turquoise: Earned 5,000,000 credits (7,342,780)TPS LLR (retired) Bronze: Earned 10,000 credits (34,130)TRP LLR Jade: Earned 10,000,000 credits (19,866,589)Woodall LLR Turquoise: Earned 5,000,000 credits (8,171,820)321 Sieve Sapphire: Earned 20,000,000 credits (20,236,219)Cullen/Woodall Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,383,853)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,626,419)PPS Sieve Emerald: Earned 50,000,000 credits (76,969,144)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Ruby: Earned 2,000,000 credits (2,293,882)TRP Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,012,757)AP 26/27 Sapphire: Earned 20,000,000 credits (21,918,894)GFN Emerald: Earned 50,000,000 credits (76,466,089)PSA Ruby: Earned 2,000,000 credits (2,939,755)
Message 147218 - Posted: 31 Dec 2020 | 16:50:49 UTC - in response to Message 147209.

Does the program Project Lasso assist in keeping them on the real cpu cores and away from the HT ones?

As I understand it they're the same - with HT on each physical core has 2 virtual cores.


That's my understanding also, the two threads exposed are not different from each other from that perspective, but are backed by the same core. Neither are "more real" than the other. So in that sense, it doesn't matter which of the two you use, as long as you only use one of them at a time. In the single thread task scenario, I suspect Windows is NOT doing that if left to run by itself.

If I need to intervene that way, I'd just go into Task Manager, select the boinc process (not the manager) and set it to either all odd or all even numbered "processors". Windows seems to balance ok once you do that.

Process Lasso probably can do it also, but I didn't use it outside of a different performance optimisation required for Zen CCX considerations. I've since chose a different solution to that which is not to own any Ryzen CPUs.

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321 LLR Turquoise: Earned 5,000,000 credits (7,879,763)Cullen LLR Turquoise: Earned 5,000,000 credits (6,828,213)ESP LLR Turquoise: Earned 5,000,000 credits (5,055,512)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (6,457,215)PPS LLR Turquoise: Earned 5,000,000 credits (8,645,607)PSP LLR Turquoise: Earned 5,000,000 credits (6,104,395)SoB LLR Jade: Earned 10,000,000 credits (10,245,712)SR5 LLR Turquoise: Earned 5,000,000 credits (6,730,319)SGS LLR Turquoise: Earned 5,000,000 credits (5,334,462)TRP LLR Jade: Earned 10,000,000 credits (10,009,531)Woodall LLR Turquoise: Earned 5,000,000 credits (6,638,546)321 Sieve Sapphire: Earned 20,000,000 credits (20,019,388)Cullen/Woodall Sieve (suspended) Double Silver: Earned 200,000,000 credits (265,102,350)PPS Sieve Double Gold: Earned 500,000,000 credits (546,715,203)TRP Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,801,812)AP 26/27 Emerald: Earned 50,000,000 credits (61,259,536)GFN Double Silver: Earned 200,000,000 credits (249,675,265)
Message 147221 - Posted: 31 Dec 2020 | 18:47:56 UTC - in response to Message 147218.

(From memory, it's been a while since I checked) windows does something weird like using 7/8 "real" cores when running 8 single threaded tasks on a 16 virtual core system.

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Found 1 prime in the 2019 Tour de PrimesFound 5 primes in the 2020 Tour de Primes321 LLR Ruby: Earned 2,000,000 credits (2,216,329)Cullen LLR Ruby: Earned 2,000,000 credits (2,826,433)ESP LLR Ruby: Earned 2,000,000 credits (2,253,924)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,218,841)PPS LLR Jade: Earned 10,000,000 credits (10,863,107)PSP LLR Ruby: Earned 2,000,000 credits (2,327,946)SoB LLR Ruby: Earned 2,000,000 credits (2,230,141)SR5 LLR Ruby: Earned 2,000,000 credits (2,081,611)SGS LLR Ruby: Earned 2,000,000 credits (2,037,347)TRP LLR Ruby: Earned 2,000,000 credits (4,118,961)Woodall LLR Ruby: Earned 2,000,000 credits (2,247,622)321 Sieve Ruby: Earned 2,000,000 credits (2,279,140)Generalized Cullen/Woodall Sieve (suspended) Turquoise: Earned 5,000,000 credits (6,057,633)PPS Sieve Double Bronze: Earned 100,000,000 credits (171,600,755)AP 26/27 Ruby: Earned 2,000,000 credits (2,919,046)GFN Sapphire: Earned 20,000,000 credits (21,382,838)
Message 147230 - Posted: 1 Jan 2021 | 0:10:11 UTC - in response to Message 147202.

I don't normally run GPU tasks at the same time so don't know how that changes things.


I recently tested this with the last challenge and the was no difference running the GPU using the spare threads in run times. ie - Running 16 cores on my 3950X (HT off) then crunching GFN-18 with the GPU, run times were the same as if I was crunching no CPU work and giving the GPU full cores.

At least that's what I found any way with PG.
The same can't be said for other projects where there are performance gains by reserving 1 or more cores.
____________

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Discovered 4 mega primesEliminated 1 conjecture "k"Found 3 primes in the 2018 Tour de PrimesFound 1 mega prime in the 2018 Tour de PrimesFound 5 primes in the 2019 Tour de PrimesFound 6 primes in the 2020 Tour de Primes321 LLR Turquoise: Earned 5,000,000 credits (8,774,878)Cullen LLR Turquoise: Earned 5,000,000 credits (5,903,451)ESP LLR Turquoise: Earned 5,000,000 credits (6,454,573)Generalized Cullen/Woodall LLR Turquoise: Earned 5,000,000 credits (5,122,074)PPS LLR Emerald: Earned 50,000,000 credits (83,377,417)PSP LLR Jade: Earned 10,000,000 credits (15,223,714)SoB LLR Jade: Earned 10,000,000 credits (17,319,914)SR5 LLR Sapphire: Earned 20,000,000 credits (23,996,561)SGS LLR Turquoise: Earned 5,000,000 credits (7,342,780)TPS LLR (retired) Bronze: Earned 10,000 credits (34,130)TRP LLR Jade: Earned 10,000,000 credits (19,866,589)Woodall LLR Turquoise: Earned 5,000,000 credits (8,171,820)321 Sieve Sapphire: Earned 20,000,000 credits (20,236,219)Cullen/Woodall Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,383,853)Generalized Cullen/Woodall Sieve (suspended) Sapphire: Earned 20,000,000 credits (20,626,419)PPS Sieve Emerald: Earned 50,000,000 credits (76,969,144)Sierpinski (ESP/PSP/SoB) Sieve (suspended) Ruby: Earned 2,000,000 credits (2,293,882)TRP Sieve (suspended) Turquoise: Earned 5,000,000 credits (5,012,757)AP 26/27 Sapphire: Earned 20,000,000 credits (21,918,894)GFN Emerald: Earned 50,000,000 credits (76,466,089)PSA Ruby: Earned 2,000,000 credits (2,939,755)
Message 147238 - Posted: 1 Jan 2021 | 10:51:41 UTC - in response to Message 147230.

I recently tested this with the last challenge and the was no difference running the GPU using the spare threads in run times. ie - Running 16 cores on my 3950X (HT off) then crunching GFN-18 with the GPU, run times were the same as if I was crunching no CPU work and giving the GPU full cores.

I was thinking about it from the opposite perspective, does running a GPU task interfere with the CPU task(s) running speed. For the "low CPU" GPU tasks I'd guess not, but if a GPU tasks needs more CPU time and HT is on, I'd suspect that could cause inefficiency due to uneven balancing. Obviously a "free core" with HT off is a loss in performance.

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Message boards : Number crunching : Is turning on hyper threading better if you still assign number of tasks to only pysical cores?

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