novaBBS - rec.games.backgammon - If XG said that it was lying, would you believe it?

If XG said that it was lying, would you believe it?

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Subject: If XG said that it was lying, would you believe it?
From: pepste...@gmail.com (peps...@gmail.com)
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by: peps...@gmail.com - Sun, 22 May 2022 20:20 UTC

In the below position, 21/17 is mandatory to save the backgammon.
Furthermore, there is no reason to concede the gammon -- gammon-saving
is unlikely (to put it mildly) but far from impossible.
Another conclusion (they don't call me "Oracle" for nothing) is that
the gammon-saving probability is small enough that any reasonable
play is unlikely to lose much PR.
But they also don't call me "Stickler for nothing" (they just call me a
"stickler" (Tim does anyway)) so I am keen to play this roll correctly.
XG says that 10/9 is better than the alternatives.
Is this another incident of XG's roundomania where it comes to
bizarre conclusions through rounding errors? Or is 10/9 really
the uniquely optimal play?

Thank You,
Paul

XGID=-ABCBBB--AA----------Aaab-:1:-1:1:41:1:5:3:0:10
X:Daniel O:eXtremeGammon

Score is X:1 O:5. Unlimited Game, Jacoby Beaver
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | X O O O | +---+
| | | O | | 2 |
| | | | +---+
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | X |
| | | X X X X X |
| X X | | X X X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 84 O: 7 X-O: 1-5
Cube: 2, O own cube
X to play 41

1. 4-ply 21/17 10/9 eq:-1.999
Player: 0.00% (G:0.00% B:0.00%)
Opponent: 100.00% (G:99.95% B:0.00%)

2. 4-ply 21/17 9/8 eq:-2.000
Player: 0.00% (G:0.00% B:0.00%)
Opponent: 100.00% (G:99.95% B:0.00%)

3. 4-ply 21/16 eq:-2.000
Player: 0.00% (G:0.00% B:0.00%)
Opponent: 100.00% (G:99.95% B:0.00%)

4. 4-ply 10/9 6/2 eq:-2.111 (-0.111)
Player: 0.00% (G:0.00% B:0.00%)
Opponent: 100.00% (G:99.97% B:11.11%)

5. 3-ply 21/17 2/1 eq:-1.999 (+0.001)
Player: 0.02% (G:0.00% B:0.00%)
Opponent: 99.98% (G:99.91% B:0.00%)

eXtreme Gammon Version: 2.10

Re: If XG said that it was lying, would you believe it?

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Subject: Re: If XG said that it was lying, would you believe it?
From: bananabo...@gmail.com (Stick Rice)
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by: Stick Rice - Sun, 22 May 2022 23:52 UTC

On Sunday, May 22, 2022 at 4:20:22 PM UTC-4, peps...@gmail.com wrote:
> In the below position, 21/17 is mandatory to save the backgammon.
> Furthermore, there is no reason to concede the gammon -- gammon-saving
> is unlikely (to put it mildly) but far from impossible.
> Another conclusion (they don't call me "Oracle" for nothing) is that
> the gammon-saving probability is small enough that any reasonable
> play is unlikely to lose much PR.
> But they also don't call me "Stickler for nothing" (they just call me a
> "stickler" (Tim does anyway)) so I am keen to play this roll correctly.
> XG says that 10/9 is better than the alternatives.
> Is this another incident of XG's roundomania where it comes to
> bizarre conclusions through rounding errors? Or is 10/9 really
> the uniquely optimal play?
>
> Thank You,
> Paul
>
> XGID=-ABCBBB--AA----------Aaab-:1:-1:1:41:1:5:3:0:10
> X:Daniel O:eXtremeGammon
>
> Score is X:1 O:5. Unlimited Game, Jacoby Beaver
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | | | X O O O | +---+
> | | | O | | 2 |
> | | | | +---+
> | | | |
> | | | |
> | |BAR| |
> | | | |
> | | | |
> | | | X |
> | | | X X X X X |
> | X X | | X X X X X X |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 84 O: 7 X-O: 1-5
> Cube: 2, O own cube
> X to play 41
>
> 1. 4-ply 21/17 10/9 eq:-1.999
> Player: 0.00% (G:0.00% B:0.00%)
> Opponent: 100.00% (G:99.95% B:0.00%)
>
> 2. 4-ply 21/17 9/8 eq:-2.000
> Player: 0.00% (G:0.00% B:0.00%)
> Opponent: 100.00% (G:99.95% B:0.00%)
>
> 3. 4-ply 21/16 eq:-2.000
> Player: 0.00% (G:0.00% B:0.00%)
> Opponent: 100.00% (G:99.95% B:0.00%)
>
> 4. 4-ply 10/9 6/2 eq:-2.111 (-0.111)
> Player: 0.00% (G:0.00% B:0.00%)
> Opponent: 100.00% (G:99.97% B:11.11%)
>
> 5. 3-ply 21/17 2/1 eq:-1.999 (+0.001)
> Player: 0.02% (G:0.00% B:0.00%)
> Opponent: 99.98% (G:99.91% B:0.00%)
>
>
> eXtreme Gammon Version: 2.10

I believe XG is correct for in the scenarios where your opponent rolls back to back [21]s on our second roll with various numbers we'll be able to get off with [33] or better instead of [44] or better.

Stick

Re: If XG said that it was lying, would you believe it?

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From: tchow12...@yahoo.com (Timothy Chow)
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Subject: Re: If XG said that it was lying, would you believe it?
Date: Mon, 23 May 2022 09:08:10 -0400
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by: Timothy Chow - Mon, 23 May 2022 13:08 UTC

On 5/22/2022 7:52 PM, Stick Rice wrote:
> I believe XG is correct for in the scenarios where your opponent rolls back to back [21]s on our second roll with various numbers we'll be able to get off with [33] or better instead of [44] or better.

Sounds plausible. I just did an XG rollout with 2 million trials.
Number of trials in which X saved the gammon:

21/7 10/9: 1043
21/7 9/8: 990
21/16: 987

---
Tim Chow

Re: If XG said that it was lying, would you believe it?

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Subject: Re: If XG said that it was lying, would you believe it?
From: pepste...@gmail.com (peps...@gmail.com)
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by: peps...@gmail.com - Mon, 23 May 2022 20:12 UTC

On Monday, May 23, 2022 at 2:08:14 PM UTC+1, Tim Chow wrote:
> On 5/22/2022 7:52 PM, Stick Rice wrote:
> > I believe XG is correct for in the scenarios where your opponent rolls back to back [21]s on our second roll with various numbers we'll be able to get off with [33] or better instead of [44] or better.
> Sounds plausible. I just did an XG rollout with 2 million trials.
> Number of trials in which X saved the gammon:
>
> 21/7 10/9: 1043
> 21/7 9/8: 990
> 21/16: 987
>
> ---
> Tim Chow
Oh wow! Thanks to Tim and Stick.
A one in two thousand parlay is something that could quite easily happen.
Experienced players will have received quite a few parlays like that.
I thought the gammon-saving chances were worse.
Shame on me for missing the optimal play.

Paul

Re: If XG said that it was lying, would you believe it?

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From: tchow12...@yahoo.com (Timothy Chow)
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Subject: Re: If XG said that it was lying, would you believe it?
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by: Timothy Chow - Wed, 25 May 2022 12:40 UTC

On 5/23/2022 4:12 PM, peps...@gmail.com wrote:
> On Monday, May 23, 2022 at 2:08:14 PM UTC+1, Tim Chow wrote:
>> On 5/22/2022 7:52 PM, Stick Rice wrote:
>>> I believe XG is correct for in the scenarios where your opponent rolls back to back [21]s on our second roll with various numbers we'll be able to get off with [33] or better instead of [44] or better.
>> Sounds plausible. I just did an XG rollout with 2 million trials.
>> Number of trials in which X saved the gammon:
>>
>> 21/7 10/9: 1043
>> 21/7 9/8: 990
>> 21/16: 987
>>
>> ---
>> Tim Chow
> Oh wow! Thanks to Tim and Stick.
> A one in two thousand parlay is something that could quite easily happen.

Do you mean a one in forty thousand parlay? The difference
between 21/7 10/9 and 21/7 9/8 is only about 50 in 2 million
according to the rollout.

---
Tim Chow

Re: If XG said that it was lying, would you believe it?

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Subject: Re: If XG said that it was lying, would you believe it?
From: pepste...@gmail.com (peps...@gmail.com)
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by: peps...@gmail.com - Wed, 25 May 2022 19:24 UTC

On Wednesday, May 25, 2022 at 1:40:07 PM UTC+1, Tim Chow wrote:
> On 5/23/2022 4:12 PM, peps...@gmail.com wrote:
> > On Monday, May 23, 2022 at 2:08:14 PM UTC+1, Tim Chow wrote:
> >> On 5/22/2022 7:52 PM, Stick Rice wrote:
> >>> I believe XG is correct for in the scenarios where your opponent rolls back to back [21]s on our second roll with various numbers we'll be able to get off with [33] or better instead of [44] or better.
> >> Sounds plausible. I just did an XG rollout with 2 million trials.
> >> Number of trials in which X saved the gammon:
> >>
> >> 21/7 10/9: 1043
> >> 21/7 9/8: 990
> >> 21/16: 987
> >>
> >> ---
> >> Tim Chow
> > Oh wow! Thanks to Tim and Stick.
> > A one in two thousand parlay is something that could quite easily happen.
> Do you mean a one in forty thousand parlay? The difference
> between 21/7 10/9 and 21/7 9/8 is only about 50 in 2 million
> according to the rollout.

No, I meant what I said.
I was arguing against a common line of reasoning that says
"I'll lose a gammon whatever happens, so I don't really care."
And I was making the point (or trying to) that the loss of the gammon
actually doesn't always happens but only approx 99.95% of the time.

Paul

Keep on keepin' on.

interests / rec.games.backgammon / If XG said that it was lying, would you believe it?

Subject	Author
If XG said that it was lying, would you believe it?	peps...@gmail.com
Re: If XG said that it was lying, would you believe it?	Stick Rice
Re: If XG said that it was lying, would you believe it?	Timothy Chow
Re: If XG said that it was lying, would you believe it?	peps...@gmail.com
Re: If XG said that it was lying, would you believe it?	Timothy Chow
Re: If XG said that it was lying, would you believe it?	peps...@gmail.com