Match Play

Forum Archive : Match Play

2-away/4-away: trailer's initial double

From:   Kit Woolsey
Date:   31 January 1996
Subject:   Maybe Mloner knows something

I had the following sequence when behind 3-1 in a 5-point match vs.
RainerBirkle earlier today:

1. He started with 5-4, playing 24/20, 13/8
2. I rolled 2-1, playing 13/11, 6/5*
3. He rolled 6-6, flunking

Having seen some of the positions mloner has been flinging cubes over at
this match score, I figured if it is good enough for mloner it is good
enough for me, so I doubled.

As Rainer scooped it up, it occurred to me that maybe I didn't mind this
too much.  After all I was a clear favorite, had some decent gammon
chances, and that would win the whole match for me.  As it happened
everything went my way, I pinned him back to an ace-point game and
gammoned him for the match.

Afterward, I started wondering if he even was supposed to take, since I
had realized that I didn't mind his taking.  If he passes, according to
my equity table his winning chances in the match are 60%.  I fed the
position to jellyfish for 10368 rollouts (this certainly should be
enough, and it is hard to imagine any major bias in this position).  The
results were (backgammons not included):

Rainer won gammon:      10.0%
Rainer won single:      29.5%
Woolsey won single:     40.4%
Woolsey won gammon:     20.1%

These certainly look about what one might expect.  Now, let's turn them
into match equities.  If Rainer wins the game (gammon or not) he wins the
match.  If I win a single game we are tied.  If I win a gammon, I win the
match.  Thus, Rainer's match equity if he takes the double according to
the rollouts is:

39.5% X 1.00   +
40.4% X  .50   +
20.1% X    0

This comes to 39.50 + 20.20 = 59.70%.  This is less than the 60% he would
have had if he passed, so it looks like he actually has a bare pass!

Look at the implications.  While this was a very small market loss for me,
there were clearly much bigger ones available -- I might have crushed him
with 1-1, 3-3, 4-4, or 5-5 and then if he had flunked the market loss
would have been big.  This is not to suggest that I should have doubled
after his opening 5-4 -- I'm not even a favorite yet, so the cost when I
lose a single game and lose the match (instead of being behind 4-1 for 17%
equity) appears to be greater than the potential gains from doubling.
What it does show is just how little an edge one might need to double at
this score, provided there is some decent volatility and gammon potential.
Looks like mloner's early doubles at this match score aren't so foolish
after all.

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Match Play

1-away/1-away: advice from Bernhard Kaiser  (Darse Billings, July 1995)  [Long message] [Recommended reading]
1-away/1-away: advice from Stick  (Stick+, Mar 2007)  [GammOnLine forum]
1-away/1-away: and similar scores  (Lou Poppler, Aug 1995) 
2-away/3-away: playing for gammon  (Tom Keith, Feb 1996) 
2-away/4-away: Neil's rule of 80  (Neil Kazaross, June 2004)  [GammOnLine forum]
2-away/4-away: cube strategy  (Tom Keith, Dec 1996) 
2-away/4-away: practical issues  (Mark Damish, Jan 1996) 
2-away/4-away: trailer's initial double  (Kit Woolsey, Jan 1996) 
3-away/4-away: opponent's recube  (William C. Bitting+, Feb 1997)  [Long message]
3-away/4-away: racing cube  (Bill Calton+, Nov 2012) 
3-away/4-away: tricky cube decision  (Kit Woolsey+, July 1994) 
3-away/4-away: what's the correct equity?  (Tom Keith, Sept 1997) 
4-away/4-away: take/drop point  (Gary Wong, Oct 1997) 
5-away/11-away: redouble to 8  (Gavin Anderson, Oct 1998) 
7-away/11-away: volatile recube decision  (Kit Woolsey, May 1997) 
Both too good and not good enough to double  (Paul Epstein+, Sept 2007) 
Comparing 2-away/3-away and 2-away/4-away  (Douglas Zare, Mar 2002) 
Crawford rule  (Chuck Bower, May 1998) 
Crawford rule  (Kit Woolsey, Mar 1997) 
Crawford rule--Why just one game?  (Walter Trice, Jan 2000) 
Crawford rule--history  (Michael Strato, Jan 2001) 
Delayed mandatory double  (tem_sat+, Oct 2010) 
Delayed mandatory double  (Donald Kahn+, Dec 1997)  [Recommended reading]
Doubling when facing a gammon loss  (Kit Woolsey, Jan 1999) 
Doubling when opponent is 2-away  (David Montgomery, Dec 1997) 
Doubling when you're an underdog  (Stein Kulseth, Dec 1997) 
Doubling window with gammons  (Jason Lee+, Jan 2009) 
Free drop  (Ian Shaw, May 1999) 
Free drop  (Willis Elias+, Oct 1994) 
Gammonless takepoint formula  (Adam Stocks, June 2002) 
Going for gammon when opp has free drop  (Kit Woolsey, Jan 1998) 
Going for gammon when opp has free drop  (Kit Woolsey, Apr 1995) 
Holland rule  (Neil Kazaross, Apr 2010) 
Holland rule  (Kit Woolsey, Dec 1994) 
Leading 2-away with good gammon chances  (Douglas Zare, Feb 2004)  [GammOnLine forum]
Match play 101  (Max Urban+, Oct 2009) 
Matches to a set number of games  (Tom Keith+, Oct 1998) 
Playing when opponent has free drop  (Gilles Baudrillard+, Dec 1996) 
Post-crawford doubling  (Scott Steiner+, Feb 2004) 
Post-crawford doubling  (Maik Stiebler+, Dec 2002) 
Post-crawford doubling  (Gus+, Sept 2002) 
Post-crawford mistakes  (Rob Adams, Sept 2007)  [GammOnLine forum]
Post-crawford/2-away: too good to double  (Robert-Jan Veldhuizen, July 2004) 
Slotting when opponent has free drop  (onur alan+, Apr 2013) 
Take points  (fiore+, Feb 2005)  [GammOnLine forum]
Tips to improve cube handling  (Lucky Jim+, Jan 2010) 
When to free drop  (Dan Pelton+, Oct 2006) 
When to free drop  (Tom Keith+, July 2005)  [GammOnLine forum]
When to free drop  (Gregg Cattanach, Dec 2004)  [GammOnLine forum]
When to free drop  (Kit Woolsey, Feb 1998) 
When to free drop  (Chuck Bower, Jan 1998) 
Which format most favors the favorite?  (Daniel Murphy+, Jan 2006)  [GammOnLine forum]

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