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Re: [bug-gnubg] bug in gammon-save eval
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From: |
Ned Cross |
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Subject: |
Re: [bug-gnubg] bug in gammon-save eval |
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Date: |
Sat, 26 Apr 2003 08:54:08 -0700 |
----- Original Message -----
Sent: Saturday, April 26, 2003 2:35
AM
Subject: Re: [bug-gnubg] bug in gammon-save
eval
> On Fri 25 Apr 2003 (13:45 -0700), Ned
Cross wrote:
> > GNU is choosing a move that loses more gammons because
it has a fantasy that there are actual game-winning chances from this
position. Very strange.
> >
> > -Ned
> >
> >
> > black (O, 10 pts) vs. white (X, 1 pts) (Match to
15)
> >
> > Game number 6
> >
> > Match
Information:
> >
> > black's rating: n/a
> > white's
rating: n/a
> > Date: n/a
> > Event: n/a
> > Round:
n/a
> > Place: n/a
>
> > Annotator: n/a
> >
Comments: n/a
> > Move number 47: X to play 34
> >
>
> GNU Backgammon Position ID: HQAAYLYbsgAAAA
>
>
Match ID : UYnxAaAACAAA
> >
+13-14-15-16-17-18------19-20-21-22-23-24-+ O:
black
> > |
X
|
|
O O | OOO 10 points
> >
|
|
|
O | OO
> >
|
|
|
O | OO
> >
|
|
|
| OO
> >
|
|
|
| OO
> >
v|
|BAR|
| 15 point match
> >
|
|
|
|
> >
|
|
|
|
> >
|
| |
X
|
> > |
X
| | X X X X X
| Rolled 34
> > |
X
X | | X
X X X X | 1
point
> >
+12-11-10--9--8--7-------6--5--4--3--2--1-+ X: white
(Cube: 2)
> > Pip counts: O 7, X 90
> >
> > * white
moves 13/6
> >
> > Cube analysis
> > 2-ply cubeless
equity -1.630 (Money: -1.936)
> > 0.000 0.000
0.000 - 1.000 0.936 0.000
> > Cubeful equities:
>
> 2-ply cubeful 100% speed [world class]
> > 1. No
double
-1.630
> > 2. Double,
pass +1.000 (
+2.630)
> > 3. Double,
take -1.894 (
-0.264)
> > Proper cube action: No redouble, take (9.1%)
> >
> > Rolled 34 (-0.023):
> > 1.
Cubeful 2-ply 13/10
12/8
Eq.: -1.629
> > 0.008
0.002 0.000 - 0.992 0.974 0.000
> > * 2. Cubeful
2-ply
13/6
Eq.: -1.647 ( -0.018)
>
> 0.000 0.000 0.000 - 1.000 0.962
0.000
> > 3. Cubeful
2-ply 12/9
10/6
Eq.: -1.663 ( -0.034)
>
> 0.000 0.000 0.000 - 1.000 0.986
0.000
> > 4. Cubeful
2-ply 13/9
12/9
Eq.: -1.663 ( -0.034)
>
> 0.000 0.000 0.000 - 1.000 0.986
0.000
> > 5. Cubeful
2-ply
12/5
Eq.: -1.665 ( -0.036)
>
> 0.000 0.000 0.000 - 1.000 0.988
0.000
> > 6. Cubeful
2-ply 13/9
10/7
Eq.: -1.667 ( -0.038)
>
> 0.000 0.000 0.000 - 1.000 0.991
0.000
>
> If you have the player settings for gnubg different than
the settings you
> are using for analysis, then sometimes the analysis
will give a
> different choice of best move than the one gnubg has made.
You can see
> some very interesting results if you set the player to
expert and
> analysis to world class or supremo. Gnubg will sometimes rate
some
> moves it has made as a blunder
This was an analysis of an imported .mat
played by humans, and the "supremo" analysis is getting it wrong.
>
> But I find the analysis
odd:
>
> There's no contact and X has pieces off. So gammon chances
are, by
> definition, zero. And chances of winning are also 0. So where do
the
> .008 and .002 numbers for win/win gammon come on the top move in
the
> analysis?
That's the real question here i
think. Is it a bug in the code feeding inputs to the race net, or just a
minor anomaly of the net?
>
> The second thing is that O is
going to be off in 2 rolls worst case,
> no matter what. The only slight
chance gnubg has to save the gammon is
> to get one man in with this roll,
then roll a high double on the next
> one. 13/10 12/8 is a guaranteed
gammon losing move, as even a high
> double on the next roll will only get
all the men in, none will be
> borne off.
I was thinking the same thing too
initially, then I saw that if O rolls 21 twice then X gets another roll to
save gammon.