Life In 19x19

Hi,

If you enjoy playing with pachipachi bot on kgs there's a little fundraising going on at the moment to buy new hardware.
(The hardware it was running on for the last 5 years just died !)

Many people find it useful and it'd be great to run it as a community supported project (until now i've been paying for all the costs).
It's running on a Raspberry Pi so costs are pretty low, we're looking at about 70€ for a Raspberry Pi 4.
(I made some calculations, if every player it played with in the last year gives 1$ that should be enough for the next 100 years' worth of hardware !)

If you'd like to participate or show support feel free to join in !
Support page is at https://pachi.or.cz (scroll down for donate button).
More details on kgs pachipachi info page.

Many thanks to everyone who contributed to Pachi in last years, go players in particular.
Finding blunders in games has been so helpful lately to make it better.
Thanks for playing =)

I am pleasantly surprised by Pachi's game! launched into sabaki, 5 seconds per turn
Zenith Go 7, 3d - Pachi

Pachi 10 s/m - Zenith Go 7, 4d

Pachi 12.86 pre-release is out:

• katago cpu build
• added --modern-joseki option
• many fixes (rave, playout, mm, seki ...)
• updated joseki fixes database

Have fun =)
Let me know if you see anything broken.

Hello!

Checking in on Pachi for one of my new Go project:

lemonsqueez wrote:Pachi 12.86 pre-release is out:
katago cpu build

Could you expand on what is exactly the KataGo CPU build? how is it different with the former Pachi? how is this different with KataGo? will there be two branches of Pachi in the future, or is this KataGo version the only version of Pachi going forward?

Thanks!

So, I checked a bit more during L19's break, and if my understanding is correct, Pachi now uses Katago's to get the "policy network values" from a board position, and use that as a starting point for MonteCarlo evaluation. Is that correct?

pnprog wrote: Fri May 30, 2025 7:22 am Could you expand on what is exactly the KataGo CPU build? how is it different with the former Pachi? how is this different with KataGo? will there be two branches of Pachi in the future, or is this KataGo version the only version of Pachi going forward?

Hi,
By default Pachi uses KataGo as joseki engine to fix some joseki sequences it plays badly otherwise (typically either newer josekis that appeared after the dcnn was trained, or josekis that are too tricky for it to handle correctly). If one of these is encountered during a game it calls KataGo to finish the sequence if it doesn't have the answer in its database.
In a game KataGo will typically play 10-15 moves in one corner if that happens.

This is by no means mandatory:
Running Pachi with '--nojosekifix' option disables all joseki fixes (standalone Pachi, KataGo not needed).

The KataGo binary is for convenience. It's just a cpu build of KataGo (nothing Pachi specific in it).
It can be used independently to play against KataGo (performance won't be as good as a gpu build though).

So, I checked a bit more during L19's break, and if my understanding is correct, Pachi now uses Katago's to get the "policy network values" from a board position, and use that as a starting point for MonteCarlo evaluation. Is that correct?

No, Pachi still uses its own dcnn internally otherwise it would be 7d =)

Hope that helps,
Cheers.

lemonsqueez wrote: Mon Mar 16, 2026 1:19 pm By default Pachi uses KataGo as joseki engine to fix some joseki sequences it plays badly otherwise (typically either newer josekis that appeared after the dcnn was trained, or josekis that are too tricky for it to handle correctly). If one of these is encountered during a game it calls KataGo to finish the sequence if it doesn't have the answer in its database.
In a game KataGo will typically play 10-15 moves in one corner if that happens.

Thanks, this cleared the confusion on my side. And this raises a new question

Since Katago comes without a Joseki dictionary, how do you use get the information from Katago? Do you just assume that any move in a corner is a joseki move, or something similar?

I do not know how Pachi does it but my study with KataGo has let me redefine joseki as "correct sequence for several standard openings judged by KataGo with sufficiently many playouts".

pnprog wrote: Thu Apr 02, 2026 11:49 pm Since Katago comes without a Joseki dictionary, how do you use get the information from Katago? Do you just assume that any move in a corner is a joseki move, or something similar?

Pretty much, yes. Early on every move in the corner is a joseki move =)

Pachi 12.90 pre-release is out:

• Seki fixes
• Slightly better playout balance
• Better random number generator
• GoGui: RAVE & Criticality visualization

Have fun =)