Forum Archive : Rollouts

Rollout settings

From:   Lokicol
Date:   12 April 2010
Subject:   Snowie settings
Forum:   Twoplustwo forum

What settings should I use to have an almost perfect rollout with snowie?

Bill Robertie  writes:

The real question is accuracy per unit of time. If time is no problem, just
use Snowie 3-ply cubeful rollouts for 2592 trials and you'll get the best
answer available, although you might wait a couple of days on even today's
fast machines.

A few years ago I tried to solve this problem using the earliest version of
Snowie 4.0. I created a suite of 50 cube problems covering all of the major
position types, and rolled them out using Snowie 3-ply cubeless, 1296
trials. The result of this I accepted as the "correct" answer for each
problem. I then duplicated the rollouts for various combinations of trial
length and ply level, as well as Snowie's raw evaluations on each ply

The results of this experiment showed a sweet spot at 2-ply cubeless, 648
trials, so that's what I used as my rollout settings for a long time. The
exception were various sorts of non-standard or backgame positions, where I
didn't trust anything less than Snowie 3-ply.

Lately, as a result of some positions published in this forum, I've
upgraded my rollouts to 2-ply cubeful, 1296 trials. There was more of a
discrepancy between the cubeful and cubeless rollouts than I originally
expected, and although these new settings take longer, especially in early
game positions, I think the time is worth it.

Peter Hallberg  writes:

Here are some crude guidelines:

* In a attacking position it's ok to use truncated rollouts.

* In priming games use full rollout.

* As a really good estimate of whether the equity is going to change on
  rollout (compared to 3-ply eval) do a 1-ply full 1296 games. If the
  equity is pretty much the same as 3-ply I usually don't want to put much
  more effort into it.

* You often need to make more precise rollouts for cubes because the right
  plays is determined by the equity. Selecting a move is less sensitive to
  error margin because you just want to know which move is best rather than
  how good it actually is.

As a note: With Gnu and XG you have excellent ways to stop a rollout based
on confidence interval and they are way faster than Snowie.
Did you find the information in this article useful?          

Do you have any comments you'd like to add?     



Advice  (David Montgomery, Apr 1996)  [Long message]
Cautionary tale  (Kit Woolsey, Sept 1995) 
Combining rollouts  (Gregg Cattanach+, Dec 2003)  [GammOnLine forum]
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)  [GammOnLine forum]
What is a rollout?  (Gregg Cattanach, Dec 1999) 

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