It is a moot point anyway, all chess prorams will suffer this effect on a HT system no matter if they use HT or not. And no matter how many threads they are running 1, 4, or 8. So this is not a the cause. The 10% is relative to programs running in HT or with HT off.lkaufman wrote:I don't have two identical computers so I can't test this myself. I think a 10% speed difference is a good estimate. This would probably mean about 15 elo at the bullet speeds we are talking about.lkaufman wrote:I am not a hardware expert so I won't presume to try to explain why, but as far as I know everyone who has compared performance of any engine with HT disabled and with HT enabled, but in each case with threads set to equal real cores, has found that performance is better with HT disabled, typically by 10 to 15 %. Whether being able to set threads to twice the number of cores provides Stockfish enough benefit to offset this I don't know, although I rather doubt it. It pretty clearly is not the case with Houdini, and with Komodo my best guess from all evidence is that Komodo runs better on 8 threads than on 4 on an i7 with HT on, but better still with 4 threads and HT off.mwyoung wrote: I have 7 computers in my house, some amd, some intel. Some with Bios HT option. My engine vs engine computer I keep nothing else on but chess testing. But I can test on any of them. I was referring to my computer I run my test on. To keep the overhead the lowest for testing engine vs engine. This is why my CPU % at rest is almost 0%.
I can do many things on my other computers, like type this response.
Other testers also have many computers at their homes and are posting the results here on your HT Question.
I have run many test on this including running test positions. I get the same NPS, the same time per depth. Except for the normal variation one would expect from testing MP. That why I tested this many times to get a good average.
Larry, I don't know what more I can do or say, but let others post their results.
You need to explain your theory, how a cpu core processing 1 pipe only per core with HT on can cripple a engine, over having HT off.
The CPU is the same either with HT on or off in Bios. ALL the bios HT ON/OFF option does is keep the programs restricted to 1 pipe on the core. But the 2 pipes are still there regardless of the HT setting in the BIOS.
If my results are incorrect and anything is possible that is why we test. INTEL is going to make many customers upset when running their single thread apps on their intel HT CPU. Because that is all INTEL is mostly making in CPU chips.
And if somehow this is true, I am sure we would have read about this from AMD inc.
Sorry I have to disagree, because of my testing. But others are also testing this and posting their results.
I may try affinity lock test, but this would actually give Houdini a advantage, because I could not affinity lock Stockfish since it wants to use all threads, and would suffer from the cache miss affect.
I am not seeing 10%, in my test so it would make little difference.
