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

[Jim Walker]

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.

Thanks for the confirmation Bob. I have just discovered last night what you say is true. Setting Stockfish to use 4 threads actually works better on my system. Windows 7 I think is without a doubt the best Windows OS so far.

[Jim Walker]

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.

Yes, that's what I'm getting so far. To be clear my setup is as follows.
I'm using Hiarcs 12 book for both programs. The Fritz GUI plays 2 games for each opening randomly selected. So each program plays from black and from white every time.
I admit I have a new computer and I have had to experiment to find out what the best settings are. This may have affected the outcome slightly. I now have about 700 games of Stockfish on both a Dual and my Quad. The average is about 20-25 Elo lower for Stockfish 1.6.

[Tord Romstad]

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....

I'm sure you did, and you probably got a desktop machine of the type that most people don't want in their homes these days. People prefer to spend a similar amount of money on a small notebook computer with a dual-core CPU.

I know plenty of people who could afford a quad-core computer, but I don't know anyone who actually owns one.

Same here. Hard to find single-core boxes any longer, and even dual-cores are getting rare.

Perhaps, but once again, people no longer buy boxes. I'm sure ordinary low-price laptops will ship with 8-core CPUs some day, but that day is still a few years in the future.

You also overlook that the majority of people don't own the latest and fastest hardware. Most of us keep our computers for a few years before we replace them.

By the way, you either "design for the future" or you "design for the past". The "present" is a very fleeting target.

It's not that fleeting. My computing world doesn't look very different today compared to when I got my first dual-core computer four years ago. Admittedly I buy new computers somewhat less frequently than some of the hardware enthusiasts around here, but still far more often than the average person.

Designing for the present has served me well for many years, and I don't see any reason to expect that to suddenly change.

[M ANSARI]

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...

Then let me know once you have the settings all setup and I will test again using similar conditions. By the way I found that Stockfish is extremely mature in many endgames that give Rybka 3 problems. Of course R3 is a 2 year old engine and I am sure a lot of changes have been made in R4, but I quickly analyzed through the 100 games and found that Stockfish has some superior knowledge in the endgame than most of the top professional chess engines.

[Tord Romstad]

By the way I found that Stockfish is extremely mature in many endgames that give Rybka 3 problems. Of course R3 is a 2 year old engine and I am sure a lot of changes have been made in R4, but I quickly analyzed through the 100 games and found that Stockfish has some superior knowledge in the endgame than most of the top professional chess engines.

The endgame does indeed seem to be Stockfish's strongest phase of the game, but its endgame knowledge actually isn't very advanced. We haven't made any particular efforts on making it play the endgame well, but it seems like our search just happens to be particularly efficient in the endgame. It got this way by accident rather than by design, but being an endgame nerd myself, I rather like it.