Quiescence Search doesn't improve strength

[emadsen]

So just adding QSearch to a material-only engine was +50 ELO, just adding PSTs provided +200 ELO despite the horizon effect. Finally the combination of PSTs + QSearch was worth +500 ELO in self play. Almost double of what the sum of it's parts would suggest.

Excellent. Thanks for running these tests. Convincing empirical evidence of the non-linear manner in which some chess engine features combine. Indeed the sum is much greater than the parts.

[Dann Corbit]

I am not surprised.
I guess that it boils down to branching factor.
A really good eval means a much better branching factor.
Even in pure alpha-beta, that can mean a huge speedup.

[Ras]

I guess that it boils down to branching factor.
A really good eval means a much better branching factor.

Actually, we had found the opposite to be true in this discussion because a more accurate eval gives more different evals and thus fewer beta cut-offs on the first try. What is at work here however is that while NPS decreases and BF / time to depth increase, the quality of these calculations increases considerably.

[Uri Blass]

So just adding QSearch to a material-only engine was +50 ELO, just adding PSTs provided +200 ELO despite the horizon effect. Finally the combination of PSTs + QSearch was worth +500 ELO in self play. Almost double of what the sum of it's parts would suggest.

Cool

A surprisingly large cooperative effect. I would not have expected that.

It seems, when the engine thinks a bit deeper, the effect gets larger: in Rustic, I tested this effect PST+QSearch = +600 Elo over an engine that is material only without QSearch. That suggests that, in very simple engines without other evaluation terms, this effect gets larger when the engine can reach larger depths.

1)The effect get larget until it get smaller.
If you search deep enough to solve the game without PST+Qsearch then the effect in a direct match is 0 elo.

2)Elo difference is dependent also on the order of moves and I guess that there is a significant difference in the strength of only material evaluation based only on the move generator.