[Pachi] Scoring

Gareth Davies gareth.davies at lmh.ox.ac.uk
Fri Aug 26 13:06:10 CEST 2011

The problem I'm having is the large central area pachi has made but not fully sealed off.  All the empty points in this moyo reach both live White and live Black stones and so can/should be considered dame.  Indeed, this is what the comment in the board_official_score function says in the file board.c.  I've also added some simple printf lines to my copy of board.c to try and understand how the score is calculated and, indeed, the spaces in the centre are coloured as 0 in the array ownermap when board_official_score is called and do not contribute to White's score.

Thanks for your help,

From: Petr Baudis [pasky at ucw.cz]
Sent: 26 August 2011 10:26
To: Gareth Davies
Cc: pachi at v.or.cz
Subject: Re: [Pachi] Scoring


On Thu, Aug 25, 2011 at 10:45:17AM +0100, Gareth Davies wrote:
> I've been using pachi for a short time now.  I ran into a problem yesterday where pachi (with the uct engine) passed very close to the end of a won game only to lose by 18.5 points due to a score counting technicality.  The root of the problem should be obvious from the sgf.

  It is actually not obvious to me. What is the issue?

> This lead me to start digging through the source code and I started to get lost in data and confused by dead groups.  In particular I cannot make sense of the gtp command final_score when run on the result of score.gtp.  Is there some difference between a board state that pachi wants to pass on and a board state that's fit for final_score?

  Here, final_score reports W+10, so it's fine that Pachi passed...?

  Both Pachi passing (unless pass_all_alive option is enabled) and
final_score is based on identification of dead groups. You can check
that using GTP command

        final_status_list dead

                                Petr "Pasky" Baudis
UNIX is user friendly, it's just picky about who its friends are.

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