Internation draughts EGTB generator ported to chess

[gwiesenekker]

Hi,

I had already generated the 7-piece DTM EGTBs for international draughts years ago. Generating the 8-piece DTM EGTBs has been on my bucket-list for a long time, but rewriting my old OpenMPI based EGTB generator was just too much work. AI now made it possible to do this in a reasonable time. I use AI in '1+1+1=4' mode as I like to call it, meaning ChatGPT writing code, Claude reviewing it and me deciding how to proceed if they disagree or are struggling. Two examples: both AIs suggested overly complicated solutions for multi-threaded EGTB generation that would have never scaled, but I already solved that problem in my OpenMPI generator so I could just explain them how to implement it. At a certain point both AIs agreed that the advanced cache algorithm based on 'work saved' could not be improved anymore, but my code review spotted something that lead to an additional 25% improvement. The result was that I could generate all 8-piece DTM EGTBs in about two weeks on a (rented) 64-core server with 512GB RAM and 8TB SSD disk-space. The largest generated EGTB consisted of 884,567,138,400 positions giving an uncompressed DTM size of 3.22 TiB, counting both sides at 16 bits each, the (zstd block-compressed) size is 457 GiB, or 14% of the uncompressed size. DTM EGTBs are compiled to (zstd block-compressed) WDL EGTBs for match play.

I recently picked up my (also decades old) chess program ZZZZZZ, trying to leverage all my 'before AI' ideas implemented in my international draughts program GWD. As part of this I had the AIs port the GWDEGTB generator to chess. I guess EGTB generation for chess is already quite mature and it is not my ambition to generate all 8-piece EGTBs for chess (or compare it to existing EGTB generators), but the code is available now on github (https://github.com/gwiesenekker/ZEGTB) if you want to give it a try.

GW

[Ajedrecista]

Hello Gijsbert:

Welcome to TalkChess! Thanks for your contribution.

I sometimes read damforum.nl forum (former laatste.info/bb3) and I see there that building EGDB is quite a thing these days, like your own thread or recent news on 12-man EGDB for English draughts/American checkers.

If you are interested in recent topics of EGTB applied to chess, there is a fairly long thread here:

Tablebase suggestion

Where there are examples of International draughts too. I know that this is too long, but just in case... good reading and good luck! Just a little teaser to encourage you: that thread helped me to realise that there are working, publicly available subsets of 8-man EGTB (WDL) for chess, casually know as 8op1 (the 8-piece tablebase only covers positions with at least one pair of opposed pawns, short op1):

https://op1-tables.info/

More info about 8op1:

https://lichess.org/@/Lichess/blog/op1- ... e/1ptPBDpC
https://github.com/niklasf/op1-tables.info
https://github.com/lichess-org/op1

Regards from Spain.

Ajedrecista.

[orac81]

I remember playing my 8k 6502 c64 checkers program in one of the late 80s Olympiads agaist an early Chinook on a Risc workstation with the 4 piece EGTBs. It won, but mine made a fair show. Now its 12 piece , how things have moved on.

At the other end of the scale, even adding the 1k v 1k db (128 bytes) improves the play of the 6502 version.

There is a 12x12 variant called Canadian Draughts, I don't think anyone has made the database for that yet. My program Dynamo will play that game.

[Ajedrecista]

Hello Adrian:

[...]

There is a 12x12 variant called Canadian Draughts, I don't think anyone has made the database for that yet. My program Dynamo will play that game.

If you want to go massive, there is also a 14×14 variant played in South Africa:

https://www.youtube.com/watch?v=rn8ogdgKGLc

Regards from Spain.

Ajedrecista.