Forum Archive : Programming

Methods of encoding positions

From:   Gary Wong
Date:   23 January 2001
Subject:   Re: Entering board positions

> In these days of human-mediated machine-to-machine communication,
> would it not be possible for your programmes to export and read a
> compact board notation? Something a bit like the Forsythe notation
> for a chess position.  A simple example of what might be possible:
>   <m/x4/o2222//o4/o4/o4/19/x/x5>
> Meaning:
> Money game.
> X owns a 4 cube.
> O has all of a double two to move.
> No men on the bar.
> O has four men each on his 1, 2  and 3 points.
> X has one man on his 2 point and five on his 1 point.

There are a few schemes for recording positions that (I think) come close
to what you want.  Jellyfish ".pos" files are perhaps the most widely
used; programs that handle it include Jellyfish (surprise!), the BBGT
FIBS client, BGBlitz, and GNU Backgammon.  The format is documented at:

FIBS "boardstyle 3" output is nice and compact, and implicitly understood
by pretty much every FIBS client out there, although it's not currently
used as an external representation.  The description is:

GNU Backgammon uses a very short text string to describe a board position;
for instance, when running on a text terminal, it shows the position you
describe as:

  GNU Backgammon  Position ID: XwAAgPceAAAAAA
  +12-11-10--9--8--7-------6--5--4--3--2--1-+     O: gnubg
  |                  |   |          O  O  O | O   Rolled 22
  |                  |   |          O  O  O | O
  |                  |   |          O  O  O | O
  |                  |   |          O  O  O |
  |                  |   |                  |
 ^|                  |BAR|                  |
  |                  |   |                X | X
  |                  |   |                X | XX
  |                  |   |                X | XX
  |                  |   |                X | XX
  |                  |   |             X  X | XX
  +13-14-15-16-17-18------19-20-21-22-23-24-+     X: gary (Cube: 4)

The "XwAAgPceAAAAAA" describes the chequer positions; the gnubg command
"set board XwAAgPceAAAAAA" will restore the above position.  The position
ID format is documented at:

Position IDs do not include the cube value, match score, player names,
etc., however; an extensible format for recording auxiliary information
like that is SGF (Smart Game Format):

and SGF for backgammon in particular:

Did you find the information in this article useful?          

Do you have any comments you'd like to add?     



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