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Re: [Bug-gnubg] GNUBG IDs and jacoby/beavers

From: Michael Petch
Subject: Re: [Bug-gnubg] GNUBG IDs and jacoby/beavers
Date: Mon, 21 Mar 2011 16:50:07 -0600
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20110303 Thunderbird/3.1.9

On 21/03/2011 3:04 PM, Philippe Michel wrote:
> I think it would be useful to have a flag for the Jacoby rule but
> that's it. You could use the same bit as for Crafword (probably with
> Jacoby on if value is zero to be backward compatible with common
> usage). The matchid format would then remain unchanged.
I considered this originally to reuse the Crawford bit and make it
Jacoby (and then reverse the meaning of the new Jacoby flag) if the
MatchLength (MatchTo) was > 0 (money session). Unfortunately previous
versions of GNUBG (including recent ones) check to see if the Crawford
flag is on when MatchTo > 0.

A simple test of the current windows build proved that out with this
python code (set up a money position, then change the crawford flag to 1:

gnubg.command ('set gnubgid yOfgATDg2+ABMA:cAkAAAAAAAAA')
ci['crawford'] = 1
newgnubgid = gnubg.gnubgid (gnubg.board(),ci,gnubg.posinfo())
gnubg.command('set gnubgid ' + newgnubgid)

You will end up with:

Illegal match ID 'sAETAAAAAAAA'
Dice 6 4, player on roll 0 (turn 0), resigned 0,
doubled 0, cube owner -1, crawford game 1,
match length 0, score 0-0, cube 1, game state 1

It ultimately ends up using this as a fallback because of the error:
If you set the Crawford flag back to 0 above and do again, all is fine.

> I suppose the idea is that when you have an gnubgid blah:blah and its
> evaluation you want to know exactly what you're talking about. But
> beavers essentially don't happen beyond ply 0 when a bot is playing
> hence their use don't change the evaluation, and at ply 0 the numbers
> are easy to interpret.
Good point.

One place where we can seem to reuse bits at least for money sessions
and appears to be backwards compatible and works with XG is in the
GammonValues (4 floats). That is a lot of bits. In Money sessions these
values seem to be completely ignored even if they have non zero float
values in them with all the software I have tried (XG, old .14.3 GNUBG
etc) . The Jacoby flag does appear to be okay if placed there. Old
software ignores it.

Michael Petch
CApp::Sysware Consulting Ltd.
OpenPGP FingerPrint=D81C 6A0D 987E 7DA5 3219 6715 466A 2ACE 5CAE 3304

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