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52S-51S-31P-42P-32 — Index to Rollouts

Posted By: Taper_Mike
Date: Thursday, 29 August 2013, at 10:41 p.m.

In Response To: 501 Essential Backgammon Problems #45 -- Rollout + Variants (Igor)

52S-51S-31P-42P-32
Position ID: mOfgASiw5+ABJA Match ID: 8IlJAAAACAAE

### Attacking the Blots

Thanks, Igor, for keeping these problems coming. Your analyses and variants are spot on.

I would have missed this one. Because 54, 44, and 22 are blocked, bringing a checker down from the midpoint risks only 7 shots. The resulting builder on the 10pt works to make both the 4pt and the bar point. That seemed a fair balance of risk and reward.

The gammon-go result suggests why “crossing” the bar with C = 24/22 8/5 does so well. Unlike S = Z = 24/22 13/10, C brings a builder within direct range of the opponent’s blots. The stripped 8pt provides what Magriel termed a semi-active builder. When POH is possible, the 8pt is expendable.

For later searching, here is a list of the obvious move sequences that lead to the position of Problem 45.

• 31P-42P-52S-51S-32
• 31P-51S-52S-42P-32
• 52S-42P-31P-51S-32
• 52S-51S-31P-42P-32

Mike

52S-51S-31P-42P-32 — Unlimited Games
XG 2.10 3-ply, Cubes: XGR 94782038 +174 j[C S14] "<=20 Igor Erovenko
GnuBg 0.xx 2-ply Trunc 725028711 +148.030 n[C S15] /0.360t Taper_Mike
XG 2.10 XGR++ Eval [XGR++ seed] +178.9 n[C S21] "&e Taper_Mike

52S-51S-31P-42P-32 — Double Match Point
XG 2.10 3-ply, Cubes: XGR 94782038 +67 d[S C4] "<=15 Igor Erovenko

52S-51S-31P-42P-32 — Gammon Go
XG 2.10 3-ply, Cubes: XGR 94782038 +408 g[C S7] "<=10 Igor Erovenko

52S-51S-31P-42P-32 — Gammon Save
XG 2.10 3-ply, Cubes: XGR 94782038 –143 s[C S2] "<=20 Igor Erovenko

Key: C = Cross [24/22, 8/5], S = Split = Z = Reverse split [24/22, 13/10]

Explanation of nacbracs

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