[Bug-gnubg] "SetMatchID cannot handle positions where a double has been offered"

[Ingo Macherius]

Hi,

I'm debugging a playing FIBS bot which has problems with a gnubg change by 
Christitan done on January 11th in play.c. This bug showed after the gbubg 
binary was updated to a recent  gnubg CVS version.

The bot does attach gnubg to STDOUT and sends batch commands to it, parsing the 
output. For cube decisions, the pseudo code is:

String fibsboard = ... ;
String posid = calculateGnubgPositionID(fibsboard);
String matchid = calculateGnubgMatchID(fibsboard);
String[] hint = sendToGnubg(new String[] {
        "set gnubgid " + posid + ":" + matchid",
        "hint" };
if (acceptDouble(hint)) {
        ...


Here is an excerpt from the logs:
...
>FIBS: 
>board:You:inim:3:0:0:0:-1:-1:-1:0:0:5:0:3:0:0:0:-4:5:0:0:1:0:0:-5:-3:0:0:0:1:0:1:0:0:0:0:1:1:1:0:-1:1:25:0:0:0:0:0:4:0:0:0
>FIBS:
>FIBS: inim doubles. Type 'accept' or 'reject'.
<FIBS: board
>FIBS: 
>board:You:inim:3:0:0:0:-1:-1:-1:0:0:5:0:3:0:0:0:-4:5:0:0:1:0:0:-5:-3:0:0:0:1:0:1:0:0:0:0:1:0:0:1:-1:1:25:0:0:0:0:0:4:0:0:0
<gnubg: set gnubgid cB/wACrgc/ARIA:cBFgAAAAAAAA
>gnubgI'm sorry, but SetMatchID cannot handle positions where a double has been 
>offered
<gnubg: hint 1
>gnubg: 
>board:opp:gnubg:3:0:0:0:-1:0:0:0:3:5:0:0:-1:0:0:-5:4:0:0:0:-3:0:-5:0:0:1:1:1:0:-1:3:3:3:3:1:1:1:0:1:-1:0:25:0:0:0:0:0:0:0:0
<gnubg: Setting GNUBG id cB/wACrgc/ARIA:cBFgAAAAAAAA
<gnubg:     1. Cubeful 2-ply    8/5(2) 6/3*(2)               MWC:  55.34%
...

Note the "I'm sorry, but SetMatchID cannot handle positions where a double has 
been offered", which breaks the approach so far used by (not only this) bot. 
Please note courtesy of threading the log entries are slightly out of order, 
but I guess still clear.

The patch causing the bot to fail is:
http://cvs.savannah.gnu.org/viewvc/gnubg/gnubg/play.c?r1=1.347&r2=1.348

Questions:
- What is the rationale of the patch, it seems that bots played very well with 
the old code (going to 2050 and above) ?
- Is there a workaround I can do other than reverting to a pre-Januaray 11th 
version?

Thx in advance,
Ingo