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Inconsistent XGR++ Evaluations -- Answer

Posted By: Nack Ballard
Date: Tuesday, 20 June 2023, at 5:22 a.m.

In Response To: Inconsistent XGR++ Evaluations (Nack Ballard)

Chris Yep was able to shed some light on the situation.

Evidently, the non-doublet equities after reaching the Nackgammon opening position (for the opponent's "opening plays" in this case) are affected by Opening Book.

"Use Opening book" can be checked or unchecked in Options/Settings/Analysis (lower left of window). David and I, for example, have this feature turned off most of the time. Others have it turned on.

Moreover, different versions (primarily of Opening book in this case) generate different equities. If you look under Help/About/Information, you'll see details about your XG version, engine version, bearoff data base, and opening book version (if you've checked the "Use Opening book" box as described in the previous paragraph). Currently, David and Chris have 3.71 (released in 2015). Mine is a modest 3.40.

3.06: 7/9/2011
3.10: 7/28/2011
3.20: 1/2/2012
3.30: 5/31/2012
3.40: (late 2012?)
3.70: 11/24/2013
3.71: (2015?)

The same divergence occurs between versions when you pre-roll to the regular backgammon opening position. For that situation, too, Opp's doublets are unaffected by Opening book, but his/her non-doublets are.

Chris acknowledges that the overall situation is not quite so simple, because there are threading issues. However, by my observation, I believe these usually explain much smaller differences, on the order of .0001 or .0002 that will sometimes affect rounding of a .001. I see that Philippe discusses threading at message 210909. (Sorry, I have to brush up on html for links.)

Chris also addressed the issue (raised by Bob) of the XGID numbers differing. It has to do with the player on roll during export to bgonline, and whether Player on Roll always at bottom is checked. Evidently, Tim figured that out, too (see message #210911).

Thanks, Chris!

Nack

		White is Player 2 score: 0 pip: 194 Unlimited Game Jacoby Beaver pip: 197 score: 0 Blue is Player 1
XGID=-bb---D-C---dD---c-d---AAB:0:0:1:21:0:0:3:0:10
Blue to play 21

1.	XG Roller++	Bar/24 Bar/23	eq: -0.0813
	Player: Opponent: 48.07% (G:12.40% B:0.56%) 51.93% (G:14.34% B:0.76%)

eXtreme Gammon Version: 2.10

Messages In This Thread

• Inconsistent XGR++ Evaluations
  Nack Ballard -- Friday, 16 June 2023, at 7:45 p.m.
  • Inconsistent XGR++ Evaluations
    Timothy Chow -- Saturday, 17 June 2023, at 3:09 a.m.
    • Inconsistent XGR++ Evaluations
      Nack Ballard -- Saturday, 17 June 2023, at 12:36 p.m.
      • Inconsistent XGR++ Evaluations
        Colin Owen -- Saturday, 17 June 2023, at 5:10 p.m.
      • Inconsistent XGR++ Evaluations
        Nack Ballard -- Monday, 19 June 2023, at 12:19 a.m.
  • Inconsistent XGR++ Evaluations
    Michael Depreli -- Saturday, 17 June 2023, at 8:29 a.m.
  • Inconsistent XGR++ Evaluations
    Jason Lee -- Sunday, 18 June 2023, at 10:41 a.m.
    • Inconsistent XGR++ Evaluations
      Bob Koca -- Monday, 19 June 2023, at 5:57 a.m.
      • Inconsistent XGR++ Evaluations
        Nack Ballard -- Monday, 19 June 2023, at 7:06 a.m.
        • Inconsistent XGR++ Evaluations
          Timothy Chow -- Monday, 19 June 2023, at 11:07 p.m.
  • Inconsistent XGR++ Evaluations
    Bob Koca -- Monday, 19 June 2023, at 3:52 a.m.
    • Inconsistent XGR++ Evaluations
      Timothy Chow -- Monday, 19 June 2023, at 4:47 a.m.
      • Inconsistent XGR++ Evaluations
        Philippe Michel -- Monday, 19 June 2023, at 6:32 p.m.
  • Inconsistent XGR++ Evaluations -- Answer
    Nack Ballard -- Tuesday, 20 June 2023, at 5:22 a.m.