[Computer-go] ladder

David Fotland fotland at smart-games.com
Tue May 14 18:45:22 PDT 2013


Many Faces reads ladders in both the tree and the play outs.  In play-outs
we already had a rule "don't play self atari (with many exceptions)".  A
similar rule is "don't play a move that is captured in a ladder (with many
exceptions)".  The moves that play out the ladder are not made in the
play-out itself, but ladders are evaluated as mart of the play-out move
generation policy.  Once you have heavy play-outs, the overhead of reading
ladders is not very high.

 

In the tree portion, I use the Many faces of Go engine to bias moves, and it
does tactical local search for up to 3 liberties, not just simple ladders.

 

David

 

From: computer-go-bounces at dvandva.org
[mailto:computer-go-bounces at dvandva.org] On Behalf Of Don Dailey
Sent: Tuesday, May 14, 2013 8:51 AM
To: computer-go at dvandva.org
Subject: Re: [Computer-go] ladder

 

I was curious about this myself.   I am so heavily involved in computer
chess that I'm having trouble keeping up with Go.     But I am amazed at how
strong the 19x19 go programs when I know that ladders are a big part of go
and that they are not easily dealt with in playouts.   

 

So if I understand this correctly,  you do significant analysis in the tree
portion of MFGO but not in the playouts?    Is that pretty typical of the
best programs? 

 

Don

 

On Tue, May 14, 2013 at 11:41 AM, David Fotland <fotland at smart-games.com>
wrote:

I'm not sure I understand exactly what you are asking, but I think neither
is true. 

 

Many MCTS programs read ladders as part of move generation or bias.  For
example ladder status may be part of the pattern data used for move bias in
the UCT tree.  During play outs, some programs use ladder status to select
the move to play.  For example a local response to the last move might be
"If the last move put a stone in atari, play in the liberty of the stone in
atari, provided it is not captured in a ladder".   Many Faces uses ladder
status in these ways.

 

I don't think a program should play out the ladder in the play out, since
half the moves are very bad.

 

David

 

From: computer-go-bounces at dvandva.org
[mailto:computer-go-bounces at dvandva.org] On Behalf Of Chun Sun
Sent: Tuesday, May 14, 2013 7:22 AM
To: computer-go at dvandva.org
Subject: [Computer-go] ladder

 

Hi... do MCTS programs usually put a specific ladder branch, or this branch
should be automatically generated given the right implementation? 

 

This question has been hoovering in my head for a while and I wanted to take
the shortcut to ask here :)

 

Thanks,

Chun


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