First, here's a regular problem for you to ponder.

XGID=-a-aB-D-B--AbD---d-dcB----:0:0:1:43:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O O X |
| X O | | O O X |
| X O | | O O |
| X O | | O |
| | | |
| |BAR| |
| | | |
| | | X |
| | | X |
| O X | | X X |
| O X X | | X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 153 O: 143 X-O: 0-0
Cube: 1
X to play 43

But now, let me do something a bit different. I'll give you a
sneak preview of the next problem I'm planning to post:

5-away/7-away recube: Double or no double?
bc7a34bd3987b179f9016cd8618ab45451619f4e4f7e80a391b20e20

I've given you just the subject line, along with a SHA3 hash of the
XGID (plus some random junk, as explained in my post, "Cryptographic
protocol"). Your task is to guess whether it's a double or not a
double from the subject line alone, without seeing the position. To
get credit for the answer, you must post your answer publicly here
on r.g.b. *before* I post the actual position. I will then reveal
the XGID (and the random junk) so that you can confirm that I did not
perform a bait-and-switch.

In order to make this challenge as fair as possible, I have done my
best to give reasonable subject lines. No dirty tricks like "Take
or pass?" for a checker-play problem or vague titles which give you
a thousand possible responses. There will be just two options to
choose from and it will be clear from the rollout which of the two
options is the correct one. I am also picking subject lines similar
in flavor to subject lines I have used before, which potentially leak
some information. For example, perhaps you have developed a sense
of what types of score-based cube actions I tend to post, so you can
use that knowledge to inform your decision when you see that my subject
line says "5-away/7-away recube". As usual, all the positions are
taken from errors from my own games that I have saved up; they have
not been specially contrived for the purpose of this game.

And just to make sure it's clear how the SHA3 hash works, here's a
test example of an XGID plus some random junk.

XGID=-a-aB-D-B--AbD---d-dcB----:0:0:1:43:0:0:0:0:10
f7ee0d7c2cda14c1a4b02183ada12106358475aea96da1ef8c8

If you go to https://www.browserling.com/tools/sha3-hash and enter
the above two lines (with a line break after the first line but
*not* after the second line of random junk) and set the output hash
size to 224, you should get:

128db7613baa6fbb9700987c50a931a28c035bddb8b6b9b4fb4f6914

I'm not sure how long I'll keep up this game, but I'll do at least a
dozen positions or so. If there is interest, I may keep it up for
longer than that.
---
Tim Chow

XGID=-a-aB-D-B--AbD---d-dcB----:0:0:1:43:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O O X |
| X O | | O O X |
| X O | | O O |
| X O | | O |
| | | |
| |BAR| |
| | | |
| | | X |
| | | X |
| O X | | X X |
| O X X | | X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 153 O: 143 X-O: 0-0
Cube: 1
X to play 43

I opted to play safe here, but XG prefers to attack. X is behind
in the pip count, and the roll is a poor one for priming. Of
attacking, racing, and priming, it seems that attacking is the
best bet.

1. Rollout¹ 13/9 6/3* eq:+0.072
Player: 52.33% (G:15.79% B:0.55%)
Opponent: 47.67% (G:15.41% B:0.67%)
Confidence: ±0.014 (+0.057..+0.086) - [100.0%]

2. Rollout¹ 13/9 11/8 eq:+0.001 (-0.070)
Player: 49.68% (G:12.68% B:0.38%)
Opponent: 50.32% (G:11.21% B:0.42%)
Confidence: ±0.013 (-0.012..+0.014) - [0.0%]

3. Rollout¹ 11/4 eq:-0.006 (-0.078)
Player: 49.33% (G:11.33% B:0.31%)
Opponent: 50.67% (G:9.37% B:0.31%)
Confidence: ±0.011 (-0.017..+0.005) - [0.0%]

4. Rollout¹ 13/6 eq:-0.012 (-0.084)
Player: 49.10% (G:12.53% B:0.37%)
Opponent: 50.90% (G:10.48% B:0.32%)
Confidence: ±0.012 (-0.024..0.000) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.207.pre-release

-------
Variant
-------

XGID=-a-aB-D-B--AdD---c-dbB----:0:0:1:43:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O | | O O X |
| X O | | O O X |
| X O | | O |
| X | | O |
| | | |
| |BAR| |
| | | |
| O | | X |
| O | | X |
| O X | | X X |
| O X X | | X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 153 O: 156 X-O: 0-0
Cube: 1
X to play 43

1. Rollout¹ 11/4 eq:+0.104
Player: 51.86% (G:12.97% B:0.33%)
Opponent: 48.14% (G:8.86% B:0.34%)
Confidence: ±0.008 (+0.096..+0.112) - [51.1%]

2. Rollout¹ 13/9 6/3* eq:+0.104
Player: 51.93% (G:16.96% B:0.63%)
Opponent: 48.07% (G:13.05% B:0.57%)
Confidence: ±0.013 (+0.091..+0.117) - [48.9%]

3. Rollout² 13/6 eq:+0.076 (-0.028)
Player: 51.06% (G:13.60% B:0.37%)
Opponent: 48.94% (G:9.23% B:0.42%)
Confidence: ±0.012 (+0.063..+0.088) - [0.0%]

¹ 2592 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

² 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.207.pre-release

---
Tim Chow