Re: [Bug-gnubg] Bearoff dB position, few questions

[Misja Alma]

Hi Alain,

Maybe gnu found the correct match score dependent play in my position
on 3-ply, but from the position one roll earlier it didn't, because
from there it had only 2-ply left to calculate the correct move ? Just
guessing ..
Good that you found another example that did give the expected result.

Cheers,
Misja

On Tue, Jun 30, 2009 at 12:03 AM, Alain
Redlinger<address@hidden> wrote:
> Hi Misja,
>
> May be in the position you indicated:
>        23YHAEC/AQAAAA:8IloACAACAAA  score -1c, -2
>        23YHAEC/AQAAAA:cIloABAACAAA  score -2, -2
> I could not see any difference in Win, gW in the Hint window at the two 
> different scores simply because the recommend move (highest
> equity) is the same for both scores ***on my machine***, contrary to what you 
> said (play safe at -2,-2; gammon go at -1c,-2).
> I find this a little bit annoying. How comes?
> Nevertheless, as I said, I think your reasoning is correct (and thank you 
> again for the explanation).
>
> So I took another position from W. Trice's, Backgammon Boot camp, where the 
> right play is clearly dependent on the score:
>
>
> The score is: GnuBG 1, Alain 4 (match to 5 points), Crawford game
> Alain to play 61
>
>    GNU Backgammon  Position ID: BgAA2LYbEAABAA
>                    Match ID   : 8AmnABAAIAAA
>    +24-23-22-21-20-19------18-17-16-15-14-13-+  O: GnuBG
> OOO | X  O             |   |                X |  1 point
> OOO |    O             |   |                  |
> OOO |                  |   |                  |
>  OO |                  |   |                  |
>  OO |                  |   |                  |
>    |                  |BAR|                  |v 5 point match (Cube: 1)
>    |                  |   |                  |
>    |                  |   |                  |
>    |             X    |   |                  |
>    | X  X  X  X  X  X |   |                  |  Rolled 61
>    | X  X  X  X  X  X |   |                  |  4 points
>    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: Alain
> Pip counts: O 4, X 84
>
>
> The best move at this score is 13/6. If loosing a backgammon, the match will 
> be decided at the next game at -1,-1. If loosing a
> gammon, the match will also be decided at the next (post Crawford) game at 
> score -1, -2, may be after a free drop. So there is no
> penalty for risking a backgammon in order to try to save the gammon (about a 
> 9% chance) and play the next game at -1,-3 with a 70%
> MWC.
> Of course at -1c,-2, X should play safe, 24/18, 13/12 to avoid loosing the 
> match by losing a backgammon, and retaining a slight
> chance of saving the gammon if rolling 66.
>
> Then I followed your idea of building a position leading to this one. I get 
> this one:
>
> The score is: GnuBG 4, Alain 1 (match to 5 points), Crawford game
> Match Information:
>
> Move number 5:  Alain to play 36
>
>    GNU Backgammon  Position ID: 23YDAiA2AAAAAA
>                    Match ID   : 8Im5AEAACAAA
>    +24-23-22-21-20-19------18-17-16-15-14-13-+  O: GnuBG
>    | O  O  O  O  O  O |   |                  |  4 points
>    | O  O  O  O  O  O |   |                  |
>    |             O    |   |                  |
>    |                  |   |                  |
>    |                  |   |                  |
>    |                  |BAR|                  |v 5 point match (Cube: 1)
>  XX |                  |   |                  |
>  XX |                  |   |                  |
>  XX |                  |   |                  |
>  XX |    X  X          |   |                  |  Rolled 36
> XXX | O  X  X          |   |                O |  1 point
>    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: Alain
> Pip counts: O 84, X 10
>
> At this score, the only possible move has the following W/L chances
>
>   1. Cubeful 2-ply    3/off(2)                     Eq.:  +2,021
>       0,987 0,928 0,682 - 0,013 0,000 0,000
>        2-ply cubeful prune [world class]
>
>
>
> But if in the same position I change the score to -1c, -3, the W, Wg etc. 
> change to:
>
>   1. Cubeful 2-ply    3/off(2)                     Eq.:  +1,420
>       1,000 0,986 0,182 - 0,000 0,000 0,000
>        2-ply cubeful prune [world class]
>
> And I can get these figures without rollouts.
> Thanks for your help.
> Alain
>
>
> -----Message d'origine-----
> De : Misja Alma [mailto:address@hidden
> Envoyé : dimanche 28 juin 2009 10:39
> À : Alain Redlinger
> Cc : address@hidden
> Objet : Re: [Bug-gnubg] Bearoff dB position, few questions
>
> Hi Alain,
>
> The position was an example of how the matchscore could influence
> checkerplays and therefore also GWC; it is true that the same move
> will give the same Win, gW etc for every score, but the point was that
> at different scores a different move was correct.
> So if you would go back in time to one roll before the position was
> reached, you would find that the position itself would have different
> Win, gW etc for different scores too.
> So in the example, place two extra checkers on the 2 point and ask gnu
> how to play 3-2 (not really a difficult problem ;)
> You'll see that the only possible move gives different Win and gW
> depending on the score.
>
> Cheers,
> Misja
>
> On Sun, Jun 28, 2009 at 1:03 AM, Alain
> Redlinger<address@hidden> wrote:
>> Thank you for your answers Misja and Massimiliano.
>> I'll answer Misja whose point is more developed.
>> Although not an advanced player, I am aware of Gammon Go / Gammon Save 
>> strategies, a GG move for example being a move of higher
>> equity, but not of highest GWC.
>> My question was whether the "Win, Wg, Wbg, Loose, Lg, Lbg" figures in the 
>> hint box were independent of the score, and what were
> they
>> exactly?
>>
>> If I take your position Misja, having Gnubg at the predefined settings 
>> supremo for checker and worlclass for cube decision
>> (evaluation). If I ask for a Hint at both scores, I get these.
>>
>> -1c, -2
>>
>>  GNU Backgammon  Position ID: 23YHAEC/AQAAAA
>>                 Match ID   : 8AllACAACAAA
>>
>> 1. Cubeful 0-ply    2/1 2/off                    Eq.:  +1,579
>>       0,993 0,297 0,001 - 0,007 0,000 0,000
>>        0-ply cubeful prune [expert]
>>    2. Cubeful 0-ply    2/off 1/off                  Eq.:  +1,257 ( -0,322)
>>       0,872 0,256 0,002 - 0,128 0,000 0,000
>>        0-ply cubeful prune [expert]
>>
>> -2, -2
>>
>>  GNU Backgammon  Position ID: 23YHAEC/AQAAAA
>>                 Match ID   : cAllABAACAAA
>>
>>    1. Cubeful 2-ply    2/off 1/off                  Eq.:  +1,367
>>       0,867 0,323 0,003 - 0,133 0,000 0,000
>>        2-ply cubeful prune [world class]
>>    2. Cubeful 2-ply    2/1 2/off                    Eq.:  +1,330 ( -0,037)
>>       1,000 0,188 0,001 - 0,000 0,000 0,000
>>        2-ply cubeful prune [world class]
>>
>>
>> These figures are hard to compare, because one is 0-ply, the other 2-ply.
>> So I made rollouts.
>>
>> ***  Rollouts  ***
>> __________________________
>>
>> -1c, -2
>>
>>  GNU Backgammon  Position ID: 23YHAEC/AQAAAA
>>                 Match ID   : 8AllACAACAAA
>>
>>    1. Rollout          2/off 1/off                  Eq.:  +1,384
>>       0,875 0,317 0,006 - 0,125 0,000 0,000 CL  +1,384 CF  +1,384
>>      [0,001 0,001 0,001 - 0,001 0,000 0,000 CL   0,002 CF   0,002]
>>        Full cubeful rollout with var.redn.
>>        1296 games, Mersenne Twister dice gen. with seed 862030641 and 
>> quasi-random dice
>>        Play: 0-ply cubeful prune [expert]
>>        Cube: 0-ply cubeful prune [expert]
>>    2. Rollout          2/1 2/off                    Eq.:  +1,362 ( -0,021)
>>       1,000 0,181 0,001 - 0,000 0,000 0,000 CL  +1,362 CF  +1,362
>>      [0,002 0,002 0,000 - 0,002 0,000 0,000 CL   0,004 CF   0,004]
>>        Full cubeful rollout with var.redn.
>>        1296 games, Mersenne Twister dice gen. with seed 862030641 and 
>> quasi-random dice
>>        Play: 0-ply cubeful prune [expert]
>>        Cube: 0-ply cubeful prune [expert]
>>
>>
>>
>> -2, -2
>>
>>  GNU Backgammon  Position ID: 23YHAEC/AQAAAA
>>                 Match ID   : cAllABAACAAA
>>
>> 1. Rollout          2/off 1/off                  Eq.:  +1,404
>>       0,875 0,317 0,006 - 0,125 0,000 0,000 CL  +1,306 CF  +1,404
>>      [0,001 0,001 0,001 - 0,001 0,000 0,000 CL   0,002 CF   0,004]
>>        Full cubeful rollout with var.redn.
>>        1296 games, Mersenne Twister dice gen. with seed 862049290 and 
>> quasi-random dice
>>        Play: 0-ply cubeful prune [expert]
>>        Cube: 0-ply cubeful prune [expert]
>>    2. Rollout          2/1 2/off                    Eq.:  +1,319 ( -0,085)
>>       1,000 0,182 0,001 - 0,000 0,000 0,000 CL  +1,319 CF  +1,319
>>      [0,001 0,002 0,000 - 0,001 0,000 0,000 CL   0,003 CF   0,003]
>>        Full cubeful rollout with var.redn.
>>        1296 games, Mersenne Twister dice gen. with seed 862049290 and 
>> quasi-random dice
>>        Play: 0-ply cubeful prune [expert]
>>        Cube: 0-ply cubeful prune [expert]
>>
>>
>> You see that the "Win, Wg, Wbg, Loose, Lg, Lbg" figures given for each move 
>> are the *same* for the same moves, *independently* of
>> the score, (-1c, -2) or (-2,-2)!
>>
>> So what are the "Win, Wg, Wbg, Loose, Lg, Lbg" figures given for each move?
>> Are they Money Game Winning chances?
>> Is match winning chance / Match equity computed from these by some formula 
>> such as:
>> MWC = Win*T(i-1,j) + Wg*T(i-2,j) + Wbg*T(i-3,j-3) + Loose*T(i,j-1) + 
>> Lg*T(i,j-2) + Lbg*T(i,j-3), at score i-away, j-away, with T
> the
>> MET ?
>>
>> Best regards
>> Alain
>>
>>
>> -----Message d'origine-----
>> De : Misja Alma [mailto:address@hidden
>> Envoyé : samedi 27 juin 2009 12:41
>> À : Massimiliano Maini
>> Cc : address@hidden; address@hidden; address@hidden
>> Objet : Re: [Bug-gnubg] Bearoff dB position, few questions
>>
>> Here's an example of a position that has different GWC depending on
>> the matchscore:
>>
>>  GNU Backgammon  Position ID: 23YHAEC/AQAAAA
>>                 Match ID   : 8AllACAACAAA
>>  +13-14-15-16-17-18------19-20-21-22-23-24-+     O: gnubg
>>  |                  | O | O  O  O  O  O  O |     2 points
>>  |                  |   | O  O  O  O  O  O |
>>  |                  |   | O  O             |
>>  |                  |   |                  |
>>  |                  |   |                  |
>> v|                  |BAR|                  |     3 point match (Cube: 1)
>>  |                  |   |                6 | X
>>  |                  |   |                X | X
>>  |                  |   |                X | X
>>  |                  |   |             X  X | XX  Rolled 21
>>  |                  |   |             X  X | XX  1 point
>>  +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: misja
>>
>> I hope it is still readable :)
>> The point is that O is on the bar and X is bearing off:
>> At the given score, trailing 1-2 crawford, X should sacrifice about
>> 13% winning chances to win 14% extra gammons and play 2/off 1/off.
>> Would the score have been 2-2 then X should of course play safe, for 100% GWC
>>
>> Misja
>>
>> On Fri, Jun 26, 2009 at 4:35 PM, Massimiliano
>> Maini<address@hidden> wrote:
>>>
>>> address@hidden wrote on 26/06/2009
>>> 15:34:56:
>>>
>>>> About the side question (purely theoretical)
>>>>
>>>> I think that there are many different equities and winning chances
>>>> implied in match play. If we want to keep things clear, the GWC
>>>> ***should *** not depend on the score. What has the match score to
>>>> do with the possibilities that a given position leads or not to
>>>> winning the game where it occurs? Clearly nothing.
>>>> It is absolutely necessary here to distinguish between Match Winning
>>>> Chance (win or loose) and Game Winning Chances (win/loose
>>>> simple, gammon, backgammon).
>>>
>>> Win/lose may be the same across different scores, but for sure gammon
>>> and backgammon percentages are not.
>>>
>>>> I would find it ***very*** helpful, at least for a beginner like
>>>> myself that would also like to have a theoretical perspective on
>>>> the game and/or software, if in the different dialog boxes of GnuBG,
>>>> it had been made explicit whether, in match play, the term
>>>> “equity” refers to match equity or the current game equity (as if it
>>>> were a money game). Currently my understanding is that money
>>>> game equity is completely irrelevant to match play, and that in a
>>>> match situation, in every window, the term equity refers to match
>>>> equity (even if expressed as NEMG), except when explicitly otherwise
>>>> mentioned.  Am I wrong about this?
>>>
>>> For match, the real thing is MWC.
>>> Conversion of MWC into EMG equities is done only for the purpose of
>>> providing an estimation of the magnitude of the gap betwen two plays
>>> in a manner that it is as independent as possible from the match score.
>>>
>>> A 1% MWC error at 0-0 to 15 could easily be a 10% error at double match
>>> point. On the other hand, the normalization to EMG equities will make
>>> the two errors similar in magnitude.
>>>
>>> MaX.
>>> _______________________________________________
>>> Bug-gnubg mailing list
>>> address@hidden
>>> http://lists.gnu.org/mailman/listinfo/bug-gnubg
>>>
>>>
>>
>>
>>
>
>
>