GNU Backgammon

Forum Archive : GNU Backgammon

Setting GnuBG's playing strength

From:   JP White
Date:   9 September 2001
Subject:   Re: Set GNU on different levels?

> What do the terms 3-ply or 2-ply mean?  Can you help me equate these
> terms into "easiest," "moderate" and "hard?"


Basically determines how many moves GNU looks ahead during it's 'thought
process' or evaluation.

0-ply in GNU terms means it isn't looking ahead any moves ahead and
'evaluates' the position as it stands to determine the best move.

1-ply means GNU looks at all 36 possible dice rolls and evaluates the
position after each roll. It then has a better idea of how the game may
turn out and it's chosen move is more likely to be correct.

2-ply is two move look ahead
3-ply 3
etc. etc.

In reality it isn't possible for GNU evaluate each and every permutation
of dice rolls and moves as this will soon grow too large. Instead it
will only evaluate moves that it initially considers in it's top x
moves. x is the number of search candidates you can configure in GNU.

Note that when you see people talking about 1-ply using Snowie this is
different. Snowie starts counting at 1. So 1-ply is no look ahead. GNU
starts counting at zero.

> I have found the Settings for players. If I set myself as "beginner"
> whatever "ply" that is), what do I set Gnubg on to give myself a fairer
> match? Or do I want to? Would cutting back on GNU's ability not be as
> good for my learning?

As someone new to backgammon it would make sense to set GNU at a lower
setting. 0-ply is the lowest setting, and that will no doubt kick butt
against you. It is possible to dumb down GNU further by increasing the
noise factor under GNU's player settings, this will force GNU to make
errors it wouldn't normally. Personally I'd start of with GNU set to
0-ply and see how you fair. If it depresses you to loose all the time,
add some noise to the occasional game. Cutting back on GNU's ability
will not be a factor for you just yet. The analysis tools are more

> Is there a way for me to raise my level as I progress? Or do I do that by
> raising GNU's level?

Raising GNU's level will give you stiffer competition. Altering the
settings for a human player is not relevant, just type in your name and
leave it at that.

Your game will improve most quickly if you spend the time to analyze the
matches afterwards and run through all the errors you made. For analysis
I'd say 2-ply reduced will be OK for checker play and 2-ply regular for
cube decisions. The higher the settings the more accurate the end
result, but the longer it will take for the analysis to complete. You
certainly don't want to dumb down GNU when it's performing an analysis
since you want to know what the best move really is.

> I'm a bit in the dark, but trying to get a handle on all of this. I wish
> GNU folks would put some of this info on their website - all about
> settings, analysis, how interpret the analysis, etc. Does everyone except
> me already know all of this?

GNU is light on help right now. It's still in Beta. It's up to someone
in the BG community to document it for the benefit of others. As yet
that hasn't occurred. So it does make it tough for you especially since
you don't know BG terminology very well. (Keep coming back here and
you'll get the help you need).

I the meantime just make sure you analyze your matches and think about
it's suggestions where it's suggested play differs from your actual
play. If you can't figure out why GNU's play is better post the position
here and you'll get plenty of help and advice. Count yourself lucky to
have GNU pointing out your each and every mistake. Most players had to
start with nothing more than a book or two and the advice of those in a
club (who wanted to win their money anyway).

> I have found the windows drop down menu, and can pull up annotation and
> game record. But nothing means much to me.

For now ignore the numbers.

Make sure in the annotation window you can see the Move column.
Your move is highlighted in red. Other candidates are in black.
The top of the list of moves is GNU's favorite, if it isn't red you
probably goofed!

> Also there is a place to select whether a move is good or bad etc - but
> it does not give me GNU's thoughts, but instead just records whatever I
> call it (i.e.- good or bad.)

In the game panel look for moves with ! or ? after them. Click on them
and you will see that GNU tells you if it's good or bad back over in the
annotation window. You shouldn't need to set it, it should already be
set for you! (Assuming you've already run an analysis on the

FYI in the game panel

?? = Very Bad
?  = Bad
?! = Doubtful
   = OK
!? = Interesting
!  = Good

You may occasionally wonder why your move which is the first ranked is
marked as bad or very bad. In that case look at the cube action analysis
and recommendation in the top of the annotation window, chances are you
missed the opportunity to double your opponent. (cube analysis isn't
always reported, only when GNU thinks it is of interest).


JP White
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GNU Backgammon

Analyzing GamesGrid matches  (Roy Passfield, Dec 2001) 
Batch analysis tool  (Øystein Johansen, June 2004)  [GammOnLine forum]
Cache size  (Ned Cross+, Mar 2004)  [GammOnLine forum]
Compiling for Windows  (Øystein Johansen, Jan 2002) 
Edit mode removing checker from bar  (Scott Steiner+, May 2003) 
Entering an annotated match  (Albert Silver, Dec 2003)  [GammOnLine forum]
Error rates: Gnu vs. Snowie  (Raccoon, Mar 2006)  [GammOnLine forum]
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) 
How to enter an illegal move  (Øystein Johansen, Aug 2003)  [GammOnLine forum]
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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