Rollouts

 Positions with inaccurate rollouts

 From: Douglas Zare Address: zare@math.columbia.edu Date: 14 October 2002 Subject: Re: rollouts, time it takes vs. accuracy of results Forum: rec.games.backgammon Google: 3DAA5DC6.4252BB27@math.columbia.edu

```> What kind of positions are not suited for rollout?

That depends on the bot. You don't want the bot to hit a lot of positions
it does not understand, hence will play badly. If you have a cubeless
rollout, you also don't want the assumptions of the adjustment to a cubeful
equity to be invalid.

With Snowie, for example, many rollouts of bearoff positions will be
inaccurate because Snowie does not understand the very low cube
efficiencies of the late bearoff. Snowie thinks that a 3-roll versus 3-roll
position is almost a take, when it is a big pass (with no effective
recubes). I know of no settings of Snowie rollouts such that 2^5 1^3 versus
1^8 is correctly identified as a money redouble.

Deciding whether to double or not, particularly when you might be too good
to double, is very hard to extract from rollouts of any current bot. They
are not good at evaluating the equity of positions that are too good to
double, hence may double too soon rather than play on in a live cube
rollout.

In Lamford's book, he claims the last problem is another example. That
position had 15 checkers on the 1-3-5 anchors, and 15 checkers on the 6-4-2
points bearing off. There is no reason for bots to understand such a
strange position, and they play it much worse than a human being might.

Douglas Zare
```

### Rollouts

Cautionary tale  (Kit Woolsey, Sept 1995)
Combining rollouts  (Gregg Cattanach+, Dec 2003)
Confidence intervals  (Bob Koca, Nov 2010)
Confidence intervals  (Timothy Chow, May 2010)
Confidence intervals  (Gerry Tesauro, Feb 1994)
Cubeless vs centered-cube rollouts  (Ron Karr, Dec 1997)
Duplicate dice  (David Montgomery, June 1998)
How reliable are rollouts?  (David Montgomery, Aug 1999)
Level-5 versus level-6 rollouts  (Michael J. Zehr, June 1998)
Level-5 versus level-6 rollouts  (Chuck Bower, Aug 1997)
Positions with inaccurate rollouts  (Douglas Zare, Oct 2002)
Reporting results of rollouts  (David Montgomery, June 1995)
Rollout settings  (Lokicol+, Apr 2010)
Settlement limit  (Michael J. Zehr, Apr 1998)
Settlement limit  (Kit Woolsey, Dec 1997)
Settlement limit in races  (Alexander Nitschke, Dec 1997)
Some guidelines  (Kit Woolsey, Apr 1996)
Standard error and JSD  (rambiz+, Feb 2011)
Standard error and JSD  (Stick+, Oct 2007)
Systematic error  (Chuck Bower, Oct 1996)
Tips for doing rollouts  (Douglas Zare, June 2002)
Truncated rollouts  (Gregg Cattanach, Oct 2002)
Truncated rollouts: pros and cons  (Jason Lee+, Jan 2006)
What is a rollout?  (Gregg Cattanach, Dec 1999)