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Ideas to compute packed positions in a chess game
Posted: Thu Sep 22, 2022 4:09 pm
by devc1
I see that every chess engine relies on move generation and evaluation speed which is almost the same between every engine. So any engine can only lookup a max of 4-6 depth without eliminating any moves.
I don't find any effective usage of SIMD in chess engines.
I guess so if you use AVX, how can we compute multiple positions. This may let us break the max of depth 6 to depth 8 or more (without eliminating moves).
Can we solve this ?
If we get a solution, it may be an evolution to the chess engines since it will search faster, eliminate less moves maybe and go deeper.
It is like using the "vpaddb" instruction to compute 32 moves at once !
Re: Ideas to compute packed positions in a chess game
Posted: Thu Sep 22, 2022 4:38 pm
by Octocontrabass
Re: Ideas to compute packed positions in a chess game
Posted: Fri Sep 23, 2022 5:57 am
by devc1
Everyone uses SIMD in chess but they only use them to compute scalar moves faster, make permutes. Not packed ones.
I want to find how to compute packed moves, which means calculating multiple moves in parallel.
I need some way to use bit manipulation in an SIMD register.
I have already looked into that page,
Re: Ideas to compute packed positions in a chess game
Posted: Fri Sep 23, 2022 10:51 am
by Octocontrabass
devc1 wrote:I need some way to use bit manipulation in an SIMD register.
It sounds like you're looking for SWAR.
Re: Ideas to compute packed positions in a chess game
Posted: Fri Sep 23, 2022 1:05 pm
by devc1
Is this an instruction set or a library of functions ?
Re: Ideas to compute packed positions in a chess game
Posted: Fri Sep 23, 2022 1:25 pm
by Octocontrabass
It's a set of techniques for operating on multiple elements within a single register, usually in ways the instruction set wasn't intentionally designed for.
For example, if AVX doesn't have an instruction for the operation you're looking for, you might look up some SWAR techniques to figure out how you can combine several instructions to get the operation you want.
Re: Ideas to compute packed positions in a chess game
Posted: Fri Sep 23, 2022 1:47 pm
by devc1
Nice, it is still not called SIMD haha : )
Thanks anyway.
Re: Ideas to compute packed positions in a chess game
Posted: Mon Sep 26, 2022 12:29 pm
by Voldemort
https://www.chessprogramming.org
As pointed by others usually have resources for what you are looking for. But I am lazy to dig deep enough to read engine source code see if they force use of SIMD instructions underneath.
I must point out that :
https://github.com/lantonov/asmFish is written in ASM, you may be change the logic to use the instructions you want by changing few functions here and there. But then I have not went far ahead reading its code.