hgm wrote: ↑Sun Jun 16, 2019 11:51 pm
Pondering makes sense when playing against Leela on a many-core machine, as Leela wouldn't use many CPU threads while thinking, and all other threads would then go to waste. Likewise the GPUs would be idle during Stockfish' turn when Leela is not pondering.
If Leela need two unshared cores, you can just set an affinity for it for hyper-threads 0-3. You can then set affinity for Stockfish to the remaining HT. That way they won't compete for cores. They might still compete for memory bandwidth, though; not sure how important that is for Leela.
I don't see why Leela couldn't run its two threads on the same physical core. That could of course be a disadvantage compared to running 2 threads on 2 physical cores, but that also holds for Stockfish' threads sharing physical cores. Yet some people claim that hyper-threading is beneficial compared to running 1 thread per physical core, and testing both under conditions with 2 active HT per core does not seem particularly unfair. It is just like all HT are somewhat slower physical cores. This doesn't involve any scheduling, so it should not be noisy.
Of course if you don't also reserve some cores for the OS, that would cause noise.
This creature is running 34 threads on a 16 core machine, and it IS affecting heavily the engines, much more Leela than SF. I don't know, I have to perform plain experiment to show black on paper what is obvious:
4 cores i7 CPU, 8 logical cores.
Leela on RTX 2070 GPU using 2 threads.
1/ Leela to 1 million nodes on 2 threads (using one of the latest nets)
without the interference from SF:
info depth 16 seldepth 52 time 35832 nodes 1021332 score cp 27 hashfull 481
nps 28503
info depth 16 seldepth 51 time 35866 nodes 1017115 score cp 27 hashfull 481
nps 28358
info depth 16 seldepth 52 time 36044 nodes 1027829 score cp 27 hashfull 483
nps 28515
Very high stability, within 0.5% deviation speeds.
2/ SF on 8 threads AND Leela to 1 million nodes on 2 threads:
info depth 16 seldepth 53 time 43960 nodes 1058510 score cp 27 hashfull 498
nps 24078
info depth 16 seldepth 52 time 48555 nodes 1017708 score cp 27 hashfull 480
nps 20959
info depth 16 seldepth 52 time 43277 nodes 999935 score cp 27 hashfull 474
nps 23105
info depth 16 seldepth 52 time 58460 nodes 1063476 score cp 27 hashfull 498
nps 18191
The speeds on average are some 30% lower and they are very erratic, some 20-30% deviation on average from one run to another.
The issue would be even graver with his 2080ti, as it uses a bit more of CPU resources than mine 2070. And more severe in shorter runs, as there are bursts of slowdowns. All in all, this creature's tests and posts here are plain garbage.