GNU Backgammon

Forum Archive : GNU Backgammon

Rollout settings

From:   Robert-Jan Veldhuizen
Date:   16 March 2004
Subject:   Re: rollout settings
Forum:   GammOnLine

Some general ideas and opinions:

A full (untruncated) rollout with 0-ply checker play will almost always
give a better result than a 2-ply evaluation.

0-ply cube is usually okay if either a cube is far away (just after a
double/take f.i.) and/or cube action doesn't seem critical (simple
position), or f.i. the position is very balanced with equity around zero
(cube errors are likely gonna even out then).

2-ply cube doesn't take too much extra time so I'd recommend that if
there's any doubt about 0-ply's cube actions. 25% speed is probably
enough, if the cube actions seem critical or you're rolling out a close
cube decision, you might wanna try 33% speed (which is VERY close to 100%
on average) or perhaps 50% or 100% speed.

2-ply checker play takes an awful lot of extra time. It seems that you
need either 50% or 100% speed here to take full advantage of better play.
The biggest speed iprovement you can get here is by using small search
filters, but at the cost of losing some accuracy (2-ply might not find
the best play because it gets filtered out at 0-ply). It's hard to say in
which positions you might want large search filters, but something like a
1.5-2 ratio from candidates to tolerance in hundredths seems to give good
compromises: 3 candidates with 0.05 tolerance (at 0-ply) for a relatively
fast rollout, 6/0.1 for medium, 8/0.15 for slow but accurate. Larger
filters than this cost a lot of extra time at (almost) no accuracy gain it

You might wanna adapt some settings to the position at hand. But that takes
experience with gnubg usually and isn't so easy. But sometimes you might be
able to guess that from your position on, there will be either more or less
candidate plays than from an "average" position.

A little more easy and practical is to adapt filters to the matchscore, I
think. F.i. at DMP, differences in EMG tend to be clearly smaller, so I
usually set the tolerance a bit lower then. At -4,-3 with a center cube,
cubeful EMG differences tend to be larger, so I increase the tolerance. Etc.

0-ply checker play is probably okay for most positions, especially if it
doesn't appear very close. But GNUBG 0-ply play is notably weak at
containment and a bit weak for difficult (prime, backgame) positions in
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GNU Backgammon

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Even-ply/odd-ply effect  (Raccoon, Nov 2004) 
Even-ply/odd-ply effect  (Tom Keith+, Oct 2003) 
Even-ply/odd-ply effect  (Scott Steiner+, Dec 2002) 
Filter settings  (Robert-Jan Veldhuizen, Nov 2004)  [GammOnLine forum]
Gnu 0.13 versus Jellyfish and Snowie  (Torsten Schoop, Aug 2003) 
Gnu 0.13 vs. Snowie 4  (Albert Silver, June 2003) 
Gnu 0.14 vs. Jellyfish  (Michael Howard+, July 2003) 
Gnu versus Snowie and Jellyfish  (Michael Depreli, Oct 2005) 
How luck factor is calculated  (Gregg Cattanach, Aug 2002) 
How rollouts work  (Gary Wong, July 1999) 
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Importing .gam files  (PAR+, Mar 2005) 
Importing PartyGammon matches  (rew+, July 2006) 
Improving your game using GnuBG  (D.U.G.+, Nov 2002) 
Installing on Windows  (maareyes, Oct 2001) 
Interpreting JSD's  (Adrian Wright+, Feb 2005)  [GammOnLine forum]
JSD's and confidence intervals  (Daniel Murphy+, Jan 2005) 
Logging rollouts  (Øystein Johansen, Oct 2004)  [GammOnLine forum]
Luck rate  (Kees van den Doel+, May 2002) 
MWC versus Equity (EMG)  (Ken+, Apr 2005)  [GammOnLine forum]
Manually entering first roll  (Andreas Graf+, Apr 2005) 
Match equity tables  (Raccoon, July 2005)  [GammOnLine forum]
Personal reflections  (Louis Nardy Pillards, Sept 2002) 
Playing two computers against each other  (Stanley E. Richards+, Mar 2008)  [GammOnLine forum]
Python scripting  (Øystein Johansen+, Nov 2004) 
Quasi-random dice in rollouts  (Ian Shaw, Mar 2004)  [GammOnLine forum]
Question marks in game list  (Jim Segrave, July 2005) 
Questions and answers  (Jim Segrave+, Jan 2003) 
Questions and answers  (Jørn Thyssen, Aug 2002) 
Restarting a rollout with different settings  (Jim Segrave, Apr 2005)  [GammOnLine forum]
Restarting a rollout with different settings  (Robert-Jan Veldhuizen, Apr 2004)  [GammOnLine forum]
Rollout settings  (geoff arnold+, Apr 2007) 
Rollout settings  (Stick+, Nov 2005)  [GammOnLine forum]
Rollout settings  (Robert-Jan Veldhuizen, Mar 2004)  [GammOnLine forum]
Rollout settings  (Ian Dunstan, Aug 2003)  [GammOnLine forum]
Rollout settings for the impatient  (Robert-Jan Veldhuizen, June 2004)  [GammOnLine forum]
Running rollouts in background  (Bruce+, Apr 2004)  [GammOnLine forum]
Saving rollout results from command-line interface  (Jeremy Bagai+, Apr 2006)  [GammOnLine forum]
Saving rollouts  (Mislav Radica+, May 2006)  [GammOnLine forum]
Setting GnuBG's playing strength  (JP White, Sept 2001) 
Setting skill level  (Jim Segrave, Apr 2004) 
Setting up and saving a rollout  (Albert Silver, Dec 2003)  [GammOnLine forum]
What's GNU?  (Gary Wong, Oct 2001) 
Which player is player 0?  (Neil Kazaross+, Oct 2004)  [GammOnLine forum]

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