Rybka 3 vs Stockfish 1.6s on Octa 4ghz 8 core

[Jim Walker]

"Isn't hyper-threading something you should stay away from? (i.e disable it in BIOS)."

I think you are right but I can't furn it off in my bios. I did just try setting Stockfish threads to only 4 and the NPS seems about the same as when it's set to 8 threads. Also the Task Manager shows the cpu usage is dropped from 100% to 50% so maybe this setting is equal to turning off hyperthreads.
Jim

[bnemias]

Isn't hyper-threading something you should stay away from? (i.e disable it in BIOS).

Yes. My understanding is that hyperthreading increases NPS slightly but has a negative effect on the search tree. Rybka 4 might use hyperthreading though, if you still like Rybka.....

While I believe it is dishonest to fudge the nps and depth values as Rybka has done to disguise its workings, Vas did find a good way to make use of the situation wrt hyperthreading. Rybka tries to relate effective nps when using hyperthreading to its (perverted) nps w/out hyperthreading.

This makes Rybka appear slower with hyperthreading enabled. Since nps is about all some people ever look at, this is an effective way to get them to turn off hyperthreading.

[tano-urayoan]

Rybka 4 might use hyperthreading though, if you still like Rybka.....
Peter

First Rybka and any engine uses hyperthreading this is a hardware configuration. If you refer that it will use it to achieve a benefit , where did you read this information about Rybka 4?

Note: Rybka could use hyperthreading more or less benefitial tuning the correct affinities in the task manager as reported by Rybka's, hardware guru Lukas Cimmiotti.

[M ANSARI]

In general hyperthreading should be turned off in the BIOS, but I think the latest OS's like Win 7 are better at handling virtual cores and can understand the difference. Theoretically it should be better to use hyperthreading ON because GUI tasks and other background processes could benefit from the virtual cores, but the OS has to understand that these are virtual cores and not laden them with chess executable tasks. This advantage would be very minimal especially with more than 4 logical cores running as the background tasks (if you have setup your system properly) would be minimal. As it is, it is better to simply turn hyperthreading OFF in the BIOS for various reasons ... mostly because it is one less thing to worry about with regards to having your setup optimized correctly (a bad hypethreading setup can cost you about 20% drop in performance) and it will allow you better overclocks, which is an advantage in chess performance.

[Jim Walker]

Overnight I ran 60 games on my quad...Stockfish1.6 vs Rybka 3 (1cpu). I set the threads in Stockfish to 4 and that seems to kill hyperthreading. The NPS of Stockfish is almost exactly the same as with 8 threads. The CPU usage drops to 50% as reported by the task manager. The performance of Stockfish is roughly the same as with 8 threads on my quad (60 games shows a slight improvement with only 4 threads). Here are my total results with Stockfish at blitz time controls,

Stockfish 1.6 is 65 Elo below Rybka 3 (4cpu) and 37 Elo behind Rybka 3 (1cpu). Stockfish has played a total of 286 games so far.
Jim

[royb]

James,

Are you saying that 4-thread Stockfish-1.6 is slightly weaker (based on your testing so far) than 1 CPU Rybka-3? I think that's what is being said, just trying to clarify.

Thanks.

[alpha123]

Rybka 4 might use hyperthreading though, if you still like Rybka.....
Peter

First Rybka and any engine uses hyperthreading this is a hardware configuration. If you refer that it will use it to achieve a benefit , where did you read this information about Rybka 4?

Note: Rybka could use hyperthreading more or less benefitial tuning the correct affinities in the task manager as reported by Rybka's, hardware guru Lukas Cimmiotti.

Yeah, I meant beneficially. I read it somewhere on the rybkaforum; I'll find the link eventually.

Peter

[bob]

I'm running Stockfish on my laptop quad. I noticed the default if 7 threads. I'm wondering why. The NPS goes up with each thread added. My computer is set to use hyperthreads and I can't turn it off so Stockfish will run 8 threads on my quadcore i720. Just curious about the 7 thread default.
Jim

If you have a decent OS, you just want to run 4 threads and leave hyperthreading on, the OS will the schedule one thread per physical core and it will work fine. If the OS is not so smart (old windows for example) then turn hyperthreading off in the BIOS (accessible when you power on). With a quad-core I would not have it turned on at all, myself.

[bob]

I live in one of the richest countries of the world, and I don't know anyone here who owns a quad-core computer. They are still very, very rare.

Really? I got my quad with 6GB DDR2 for $540USD....

Peter

Same here. Hard to find single-core boxes any longer, and even dual-cores are getting rare. By the way, you either "design for the future" or you "design for the past". The "present" is a very fleeting target.

[mcostalba]

I'm running Stockfish on my laptop quad. I noticed the default if 7 threads. I'm wondering why. The NPS goes up with each thread added. My computer is set to use hyperthreads and I can't turn it off so Stockfish will run 8 threads on my quadcore i720. Just curious about the 7 thread default.
Jim

Yes, when SF finds 8 cores then auto-limits itself to 7 threads instead of 8.

In some old (Glaurung time) test it seemed that 7 threads worked better then 8 on OCTAL machine. That's the reason it was autolimited to 7 by default. Of course you can always force to 8 through the corresponding UCI option named "Threads".

Now we have at last starting to do some much needed SMP test, see http://talkchess.com/forum/viewtopic.php?t=31388 that involves tweaking a couple of parameters that should help scaling.

Once we find the correct setup for 8 cores probably we will lift that limitation...