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21$-21S-55 (two overriding plays)

Posted By: Nack Ballard
Date: Sunday, 27 January 2019, at 4:02 a.m.

In Response To: 21$-21S-55 (two overriding plays) (Nack Ballard)

		White is Player 2 score: ? pip: 164 ? point match pip: 164 score: ? Blue is Player 1
XGID=-aa--AD-C--AdDa--c-e----B-:0:0:1:55:13:8:0:15:10
21$-21S-55

eXtreme Gammon Version: 2.10

For the position above, with Blue to play 55, find a score (the shorter the match, the better) at which, according to XGR++ evaluation, neither of the following two plays is best or second best:

.....P (Point, 13/3(2))
.....A (Attack, 8/3(2) 6/1*(2))

What is an applicable match score, and what are the two overriding plays?

You may freely consult bots.

Answer

David Rockwell submitted his answer (perfectly nactated, btw) by e-mail, claiming he had "cheated." Whether that is true is debatable, though he hadn't consulted bots in the usual sense. Although I had carefully removed the scores to the right of the diagram, I forgot about the XG ID#! That said, I have no doubt that David would have found the answer without my unintended clue.

Below is the evaluation of 21$-21S-55 at the closest score that applies:

		White is Player 2 score: 9 pip: 164 15 point match pip: 164 score: 13 Blue is Player 1
XGID=-aa--AD-C--AdDa--c-e----B-:0:0:1:55:13:9:0:15:10
21$-21S-55

1.	XG Roller++	13/8 11/1* 6/1	eq: -0.183
	Player: Opponent: 49.98% (G:17.24% B:0.56%) 50.02% (G:12.94% B:0.62%)
2.	XG Roller++	13/3 11/6 8/3	eq: -0.186 (-0.003)
	Player: Opponent: 49.98% (G:16.89% B:0.75%) 50.02% (G:12.88% B:0.64%)
3.	XG Roller++	13/3(2)	eq: -0.189 (-0.006)
	Player: Opponent: 50.77% (G:17.95% B:0.88%) 49.23% (G:13.80% B:0.88%)
4.	XG Roller++	8/3(2) 6/1*(2)	eq: -0.236 (-0.054)
	Player: Opponent: 49.23% (G:20.41% B:0.67%) 50.77% (G:14.78% B:1.02%)

eXtreme Gammon Version: 2.10

Note that I̲ (1:1:2 Inside, 13/8 11/1* 6/1) and O̥ (1:3 Outer, 13/3 11/6 8/3) leave only one blot, whereas P (Point, 13/3(2)) leaves two blots and A (Attack, 8/3 6/1*(2)) leaves three.

In a 15-point match or shorter, there are five scores for which XGR++ evaluates O̥ and I̲ as both better than P and A:

.....𣈀...[I̲ O̥3 P6 A54]
.....𣈁...[I̲ O̥3 P5 A48]
.....𣇻2 [I̲ O̥1 P2 A47]
.....𣇻4 [O̥ I̲4 P6 A51]
.....𣇻5 [O̥ I̲4 P5 A49]

Gammon Save doesn't quite qualify: s[O̥ P1 I̲5 A54].

I have rollouts for (gammon save and) any/all scores from 𣇾 to 𣇻5, if anyone is interested.

Nack

Messages In This Thread

• 21$-51S-55
  John O'Hagan -- Friday, 18 January 2019, at 8:35 p.m.
  • 21$-51S-55
    MishyPoo -- Friday, 18 January 2019, at 11:24 p.m.
  • 21$-51S-55
    David Rockwell -- Saturday, 19 January 2019, at 2:10 a.m.
    • 21$-51S-55
      neilkaz -- Saturday, 19 January 2019, at 4:52 p.m.
    • 41$-51S-55, 62$-51S-55 and 51$-51S-55
      Nack Ballard -- Saturday, 19 January 2019, at 11:53 p.m.
      • 41$-51S-55, 62$-51S-55 and 51$-51S-55
        David Rockwell -- Monday, 21 January 2019, at 5:36 p.m.
  • 21$-21S-55 (slightly different)
    Nack Ballard -- Saturday, 19 January 2019, at 5:28 p.m.
    • Table of Eight Positions (x1$-x1S-55)
      Nack Ballard -- Sunday, 20 January 2019, at 1:31 a.m.
    • 21$-21S-55 (two overriding plays)
      Nack Ballard -- Tuesday, 22 January 2019, at 12:06 a.m.
      • 21$-21S-55 (two overriding plays)
        Nack Ballard -- Sunday, 27 January 2019, at 4:02 a.m.
  • 21$-51S-55
    John O'Hagan -- Saturday, 19 January 2019, at 11:41 p.m.
    • RO in above post *NM*
      John O'Hagan -- Saturday, 19 January 2019, at 11:42 p.m.
    • 21$-51S-55
      Colin Owen -- Sunday, 20 January 2019, at 3:54 p.m.
      • 21$-51S-55
        John O'Hagan -- Monday, 21 January 2019, at 1:31 a.m.
        • 21$-51S-55
          Colin Owen -- Monday, 21 January 2019, at 3:27 a.m.
          • 21$-51S-55
            John O'Hagan -- Monday, 21 January 2019, at 3:30 a.m.