How can I switch off hyperthreading?

[Laskos]

As you can see, there is more than a 21 % increase in going from 6 to 12 threads.

Thank you. To summarize:
6 threads: 18500 kN/s
12 threads: 22400 kN/s

That is +21%, close to the 20% value I expected.
The two configurations should be nearly equal in strength, I doubt one could reliably measure any strength difference.

Robert

Isn't something strange with hash filling in Anil's run?

[Albert Silver]

The NPS reported is completely pointless and is not an indicator in any way of strength one way or the other. HT loses strength with chess engines simply due to the inefficiency of added threads.

You guys simply can't seem to see the woods for the trees ! Even Robert Houdart admits that the ELO will increase if one can achieve more than a 20% increase in the kN/s with HT on. The keywords are more than 20 %...get it ? So, instead of mindlessly repeating like parrots" HT loses strength with Chess engines" try to open your closed minds a little and and at least consider the possibility that ELO may NOT decrease ! (No offence).
On another note, I recently played a forum member kgburcham who runs dual-Xeons (12 cores) on www.come2play.com. Even using his 12 physical 'real' cores AND with the White pieces, he was barely able to hold me ( with HT on and H3 running on all 12 threads, i7 3930 k o/c to 4.8 Ghz) to a draw !
I'm almost certain I can beat him next time, with the White pieces. His userid was Houdini Program.
My userid there is sh1va..... anyone who thinks that HT is bad is welcome to challenge me. I will wipe the floor with them, that too with HT on ! If I lose, I will delete my userid there !

I withdraw what I said. If you played an entire game on Came2Play, and he barely held you to a draw, there can be no more compelling statistical evidence.

[Laskos]

Optimal Split Depth was 12.
128MB Hash: 36% increase in speed from 4 to 8 threads
4096MB Hash: 28% increase

Wow.

I have an I7-920 OC to 3.66 (3.82 with Turbo) and the increase from 4 to 8 threads with HT is about 25% (with 2048 MB of hash). How in the hell do you get those numbers?

Or the 2600 is much better in thread managements or I don't know how can you can come up with those numbers. I've never heard in any tech forum of people getting more than 65% (so about 30% increase) from HT even with OC much higher than mine.

Even my 25% I suppose is beneficial (for what I know the inefficiency from doubling cores is about 17%, so either 25% gets about +7% speed) but your 36% is really impressive.

EDIT:

P.S: Robert, if HT is indeed beneficial for the latest Intel CPU maybe it would be better if the next standard versions of Houdini accepts more cores than 6, what do you think?

I re-booted, all was clean, Win 7 installation is new, I don't know what might went wrong.

i7 2600 (not k) at 3.6 (3.8 Turbo), checked the clocks during the runs with CPU-Z, nothing was wrong. Maybe I will re-do, for now I will be on a hard test suite, comparing again 4 to 8 threads.

Kai

Another run:
128MB Hash: 31%
4096MB Hash: 27%

[shrapnel]

The NPS reported is completely pointless and is not an indicator in any way of strength one way or the other. HT loses strength with chess engines simply due to the inefficiency of added threads.

You guys simply can't seem to see the woods for the trees ! Even Robert Houdart admits that the ELO will increase if one can achieve more than a 20% increase in the kN/s with HT on. The keywords are more than 20 %...get it ? So, instead of mindlessly repeating like parrots" HT loses strength with Chess engines" try to open your closed minds a little and and at least consider the possibility that ELO may NOT decrease ! (No offence).
On another note, I recently played a forum member kgburcham who runs dual-Xeons (12 cores) on www.come2play.com. Even using his 12 physical 'real' cores AND with the White pieces, he was barely able to hold me ( with HT on and H3 running on all 12 threads, i7 3930 k o/c to 4.8 Ghz) to a draw !
I'm almost certain I can beat him next time, with the White pieces. His userid was Houdini Program.
My userid there is sh1va..... anyone who thinks that HT is bad is welcome to challenge me. I will wipe the floor with them, that too with HT on ! If I lose, I will delete my userid there !

I withdraw what I said. If you played an entire game on Came2Play, and he barely held you to a draw, there can be no more compelling statistical evidence.

Thank You !
Yes, as I said earlier, I'm certain that there are factors other than simple % of kN/s increase involved here. I've played around with the Split Depth and other parameters... maybe there are some things that just can't be quantified as Mr Robert Houdart demands !

[Lavir]

Thank you. To summarize:
6 threads: 18500 kN/s
12 threads: 22400 kN/s

That is +21%, close to the 20% value I expected.
The two configurations should be nearly equal in strength, I doubt one could reliably measure any strength difference.

Robert

However autotune is not the best way to measure real HT impact since the testing of the single positions is too short for HT to really build up fully.

The best way is to have an exact fixed time per move (as 5 minutes) and see the full node count and compare the two runs, repeating the test for different positions (opening, middlegame, ending).

As I said, my HT increase is 25%, that should be standard. I think with an 3930k configured well you can have much more, even more than what Kai has.

[Lavir]

Thank You !
Yes, as I said earlier, I'm certain that there are factors other than simple % of kN/s increase involved here. I've played around with the Split Depth and other parameters... maybe there are some things that just can't be quantified as Mr Robert Houdart demands !

I think he was being sarcastic; just saying...

[Laskos]

I re-booted, all was clean, Win 7 installation is new, I don't know what might went wrong.

LOL.

I didn't imply something got "wrong". Actually you should be happy about those results.

Probably the 2600 is (much) better for HT than my humble (as of now) 9200 (that is beginning to get old).

I wonder at this point what something like a 3930k (or similar) would be capable of, and what the difference between HT and not is with 6 threads instead than 4.

I myself was surprised. My percentages are (nps8/nps4) -1, I guess you mean the same. Anyway, very high values, curious about those 3930k and 3960X beasts.

I am more positive now that HT is beneficial on my comp. I have a collection of 100 hard positions, and even time to solutions was lower now with 8 threads. Averaged results in 3 runs:
Tactical Mode, 20 seconds/position, 1GB Hash

8 threads: 65/100, 4.8s to solution
4 threads: 58/100, 5.2s to solution

I guess a healthy 10-20 Elo points from HT.

And the last test, pretty convincing from my point of view. I took "Hard test set talkchesscom-2012" by Vincent Lejeune http://talkchess.com/forum/viewtopic.php?t=44531 consisting of 218 hard positions.

Tactical Mode, Hash 2GB, time: 60s/position

4 threads: 131/218 Average time: 11.04s
8 threads: 142/218 Average time: 10.05s

Pretty conclusive, not only significantly more solutions with 8 threads, but 10% faster to solutions. HT with its 27-36% speed-up on my comp seems clearly beneficial.

Kai

[Houdini]

Pretty conclusive, not only significantly more solutions with 8 threads, but 10% faster to solutions. HT with its 27-36% speed-up on my comp seems clearly beneficial.

Kai

Thank you for the results. Your data are very much in line with the expectation that any HT speed gain above 20% provides a real strength improvement.

It is quite possible that this only occurs with the more recent Intel CPU architectures: Sandy Bridge (i7-2600/2700/3930/3960) and Ivy Bridge (i7-3770). Possibly the larger speed gains only occur with the quad CPUs, hard to tell without further data.
Maybe someone can make the test with Houdini 3 on a i7-3770K.

Robert

[Vinvin]

And the last test, pretty convincing from my point of view. I took "Hard test set talkchesscom-2012" by Vincent Lejeune http://talkchess.com/forum/viewtopic.php?t=44531 consisting of 218 hard positions.

Tactical Mode, Hash 2GB, time: 60s/position

4 threads: 131/218 Average time: 11.04s
8 threads: 142/218 Average time: 10.05s

Pretty conclusive, not only significantly more solutions with 8 threads, but 10% faster to solutions. HT with its 27-36% speed-up on my comp seems clearly beneficial.

Kai

Nice news, Houdini 3 again +20 elo stronger !

BTW : please, send me the log of the test suite (the 2 run, if possible) via private message or in a new thread here.

Thanks,
Vincent

[Vinvin]

Nice news, Houdini 3 again +20 elo stronger !

Oops, +10% means +7 Elo, not +20 ...