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Lazy SMP >4 Thread Slowdown
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Can Cetin



Joined: 15 Sep 2017
Posts: 12

PostPost subject: Re: Lazy SMP >4 Thread Slowdown...NUMA?    Posted: Wed Nov 29, 2017 6:46 am Reply to topic Reply with quote

smatovic wrote:
...in the case of AMD Threadripper/Epyc as cpu,

do you use all 4 memory channels?

http://talkchess.com/forum/viewtopic.php?topic_view=threads&p=730500&t=64980

Code:

...Threadripper needs to be in quad channel to move from around 18'000 kn/s to over 30'000, it is was it is.



Not sure about this, but, maybe each 4 core unit of Threadripper has to be treated as NUMA node...

https://www.anandtech.com/show/11551/amds-future-in-servers-new-7000-series-cpus-launched-and-epyc-analysis/2

http://talkchess.com/forum/viewtopic.php?t=61472&highlight=numa+transposition+table

--
Srdja


I'm not actually running it on my own machine at all, I use AWS instances for testing. The particular instance works perfectly fine with stockfish (nps increases almost linearly with number of threads) but not my engine Sad haha.

abulmo2 wrote:
Good explanation here of what may happen:

https://www.youtube.com/watch?v=WDIkqP4JbkE


Will take a look thanks!
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Display posts from previous:   
Subject Author Date/Time
Lazy SMP >4 Thread Slowdown Can Cetin Wed Nov 29, 2017 1:41 am
      Re: Lazy SMP >4 Thread Slowdown...NUMA? Srdja Matovic Wed Nov 29, 2017 6:41 am
            Re: Lazy SMP >4 Thread Slowdown...NUMA? Can Cetin Wed Nov 29, 2017 6:46 am
      Re: Lazy SMP >4 Thread Slowdown Richard Delorme Wed Nov 29, 2017 6:41 am
      Re: Lazy SMP >4 Thread Slowdown Ronald de Man Wed Nov 29, 2017 10:20 am
      Re: Lazy SMP >4 Thread Slowdown Dann Corbit Wed Nov 29, 2017 4:02 pm
            Re: Lazy SMP >4 Thread Slowdown Can Cetin Wed Nov 29, 2017 6:20 pm
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