Moderators: hgm, Rebel, chrisw
Exactactly.Nordlandia wrote: ↑Sun Jun 16, 2019 11:32 pm Then again the question that arise is if ponder is good trade-off for more time
Ding ding ding a man with a brain. Happy fathers day. And there are even more effect ways to configure that also take care of the operating system.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: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.
There is a purpose to using a 32+2 thread configuration. Remember threads are not the same as utilization. And lc0 is not a ab engine. And there is more then one way to manage threads. And it drives the trolls crazy.hgm wrote: ↑Mon Jun 17, 2019 7:50 am Well, it doesn't seem to serve any purpose to use more threads in total than the number of HT provided by the hardware. So with 16 cores, 32 HT I would put Leela on 1 core, (HT 0 and 1) stockfish on 14, (HT 2-29) and reserve 1 core (HT 30-31) as a 'noise buffer' (as it seem to me it would make very little difference whether SF runs on 14 or 15 cores, and it is better to be safe than sorrow). With only 8 cores a similar approach would just leave 2 cores / 4 HT for SF, and as adding a third core would probably make a significant difference I would be tempted to run without noise buffer. As I said, contention for mamory bandwidth could still be a problem; I have really no idea whether CPU power or memory bandwidth would be the actual bottleneck, with so many cores.
Of course there are other ways to provide noise immunity, like running by node count rather than by wall-clock time.
This gives me an interesting idea. In principle pondering is still inefficient use of the CPU/GPU time that would be idle in a non-ponder game. It would be better to only use it for thinking. This is not possible in a single game, as there is no way to avoid that you have to wait for the opponent's move. But it would be possible when you played multiple (ponder-off) games in parallel. then you could run the CPU and GPU in 'batch mode', having the engines that are on move just queue up for the resource they need (i.e. one Leela queue for the GPU + 2 or 4 HT, one Stockfish queue for 28 or 26 HT, and only let their clock count down when they are actually thinking. By running some 8 games in parallel it should be quite rare that one engine thinks so much longer than average that the other queue is completely serviced, and its opponent would have to wait. The more games you run, the smaller that probability gets, and there really is no reason not to run all games of the match in parallel. (Well, perhaps hash memory.)
First I am not overloading my system. As you can see from the live stream. Let see if you can figure this out on your own.Nordlandia wrote: ↑Mon Jun 17, 2019 3:46 pm Please explain why you choose to overload your system with 32+2 threads?
8-core at 4.5GHz.mwyoung wrote: ↑Mon Jun 17, 2019 3:52 pmFirst I am not overloading my system. As you can see from the live stream. Let see if you can figure this out on your own.Nordlandia wrote: ↑Mon Jun 17, 2019 3:46 pm Please explain why you choose to overload your system with 32+2 threads?
I will give you a hint. How many threads is your compuer running right now.
That was not the question. Again how many threads are you running right now. Find the answer....Nordlandia wrote: ↑Mon Jun 17, 2019 4:16 pm8-core at 4.5GHz.mwyoung wrote: ↑Mon Jun 17, 2019 3:52 pmFirst I am not overloading my system. As you can see from the live stream. Let see if you can figure this out on your own.Nordlandia wrote: ↑Mon Jun 17, 2019 3:46 pm Please explain why you choose to overload your system with 32+2 threads?
I will give you a hint. How many threads is your compuer running right now.