Backgammon Cube Handling in Races

Cube Handling in Races

Forum Archive : Cube Handling in Races

EPC example: stack and straggler

From:   neilkaz
Address:   neilkaz@earthlink.net
Date:   6 January 2009
Subject:   Typical Trice Formula EPC position
Forum:   BGonline.org Forums

After I waited to cube we arrived at a typical Trice Formula EPC position. 24 23 22 21 20 19 18 17 16 15 14 13 +---+---+---+---+---+---+---+---+---+---+---+---+---+ OO | O | | | OO | O | | | OO | O | | | OO | O | | | O | O | | | | | | | X | | | | X | | | | X | X X | | | X | X X X X | | | X | X X X X | | O | +---+---+---+---+---+---+---+---+---+---+---+---+---+ 1 2 3 4 5 6 7 8 9 10 11 12

Christian Munk-Christensen writes:

Looks like a roll vs stack and stragler: 5 rolls * 7 + 1 = 36 for X and 3.5 * 6 + 17 = 38 for O. D/T.

Neil Kazaross writes:

We think alike but, Blue's position is clearly worse than an EPC of 5n+1 since not all doubles work.

stw writes:

Rummer asks: > I understand how to derive blues's epc: 7n + 1. Please explain the rest > of your formula as I don't know what how the 3, works. Also, in Trice's > book, I didn't understand how to determine wastage and how that is > applied to problems. The effective pip count for stack and straggler positions with 1 straggler given by Trice is 3.5 * the total number of checkers left plus the pip count of the straggler. i.e. if there are p men on the ace-point and 1 man on the q (outfield) point then the effective pip count is 3.5(p+1) + q. So in the position below White has an epc of 4 (total checkers left) * 3.5 + 16 (pip count of straggler) = 30. 24 23 22 21 20 19 18 17 16 15 14 13 +---+---+---+---+---+---+---+---+---+---+---+---+---+ OOO | O | | | OO | O | | | OO | O | | | OO | | | | OO | | | | | | | | X | | | | X | X X | | | X | X X | | | XX | X X | | | XX | X X | | O | +---+---+---+---+---+---+---+---+---+---+---+---+---+ 1 2 3 4 5 6 7 8 9 10 11 12

Bob Koca writes:

A pure 5 roll setup gives 7n + 1 = 36 and this needs to be incremented since the given position is not a pure 5 roll position. I checked and obtained +1.9 for a total of about 38. White's EPC is about 3.5*6 + 17 = 38. The guideline is that for a 5 roll position vs. a pip position that the pip player has a take down 2 in EPC. The roll player can redouble one pip earlier than that and initialdouble 2 pips earlier. So it looks like a bare initial double using that guideline. How to account for the fact that the guideline is for a pure 5 roll position? There are a couple reasons to think that blue should double slower. The first is that since this is slightly longer than a pure 5 roll position the trailer has more time to catch up. The second is that blue has a greater deviation in number of rolls to bearoff. That extra variability usually is in favor of the trailer in the race. Here though exactly how the extra 1.9 pips creeps in is important. Some of it comes from swinging 3 roll getoffs to 4 roll getoffs but those would win for blue almost always anyways. Most of it comes from swinging 4 roll getoffs to 5 roll getoffs and those have some chance of saving the win for white but remember that white was given 2 extra pips also. The swing that really helps white of 5 roll getoffs for blue becoming 6 roll getoffs hardly happen at all. If the position is an initial double for 5 roll position up 2 effective pips it will still be an initial double for the given position. For pure five roll position: Off in 3 = 7.4%. Off in 4 = 44.4%. Off in 5 = 48.2%. Off in 6 = 0%. For given position: Off in 3 = 3.4%. Off in 4 = 32.5%. Off in 5 = 60.8% .Off in 6 = 3.4%.

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