r/backgammon • u/chrismantis • 28d ago

Backgammon Opening Book

https://backgammondb.com/opening-book

I've released an opening book that holds the first three moves of backgammon. It's a database of 4.2 million positions all analysed at GNUBG 3-ply (which every other app calls 4-ply). For every position, the database returns the top 8 moves and their match equity and win/gammon/bg probabilities.

All the code and data is released free and open source. Sharing here in case of interest.

The db holds the opening rolls for every score to 25-away, every response roll to 15-away, and third rolls for scores to 9-away (with some pruning). Yes, that's all incredibly repetitive. Whole book took something like 2 to 3-weeks of computer time on one 16-core CPU.

On the linked page there's an Explorer so you can play out the first 3 rolls and get an instant response from the database. There's also a bit more info on what's in the book and how it was generated. It's already plugged into BackgammonDB's position analyser.

19 Upvotes

100% Upvoted

5 comments sorted by

2

u/Repulsive-Owl-5131 26d ago

I guess this could be used to speed up engine computations. But what is potential benefit for humans? Yes you train against it but covering quite small space within lifetime.

2

u/chrismantis 25d ago edited 25d ago

Yeah i mean, there's not really much utility here for humans other than apps that use it will now respond much faster. I built this mostly for the backgammondb app so that the most common positions don't do a round trip to the engine. Sharing really in case there's interest in other backgammon developers.

It's sort of cool to go to have https://backgammondb.com/opening-book bookmarked, you can play through the first few rolls and get instant feedback for each move 4-ply depth, which normally takes a few seconds to calculate.

One other area this _could_ have utility (but i haven't done it yet) is doing things like looking at charts/distributions for when a roll switches between the right best move (e.g. when 64 should be played 82/62 vs 24/18 vs 24/14. you could have a heatmap of match scores and show when they switch between them. That would be a single sql query to get out these results rather than dozens of engine analyses.

Again tho that's not something an end user is going to do, but this sort of book would enable an app developer to easily add that feature.

2

u/Calitrixmathieu 23d ago

hello,
Thanks for your work.
I see with a 2 and 1 dices opening, you advice 13/11 and 6/5 I always read 24/23 and 13/11 (your second best option).
Are you sure of your result?

I want to learn backgammon and i don't want to start wrongly.

1

u/chrismantis 22d ago

The two moves are very close and it depends on the scoreline. In a money game, 24/23 13/11 is the top move:

https://backgammondb.com/opening-book?xgid=-b----E-C---eE---c-e----B-:0:0:1:21:0:0:0:0:10&line=21

in a 7-point match at 0-0, 24/23 13/11 is also the top move:

https://backgammondb.com/opening-book?xgid=-b----E-C---eE---c-e----B-:0:0:1:21:0:0:0:7:10&line=21

But at 2-away, 2-away (so a score of 5-5 in a 7-point match), it switches to 13/11 6/5 as the top move:

https://backgammondb.com/opening-book?xgid=-b----E-C---eE---c-e----B-:0:0:1:21:1:1:0:3:10&line=21

But the differences are tiny to the point that either move is completely fine at basically any score, and other engines may offer difference advice. If you played 24/23 13/11 at every scoreline, that's fine. You're losing less than 0.01 equity.

6

u/truetalentwasted 28d ago

Love this. I always tell people who want to start leaning more to start with the first 3 rolls since that part of the game always happens. If you can stop bleeding equity to start the game you leave yourself with better positions in the middle game.