[computer-go] The effect of the UCT-constant on Valkyria

[Gunnar Farnebäck]

David Fotland wrote:
 > So I'm curious then.  With simple UCT (no rave, no priors, no progressive
 > widening), many people said the best constant was about 0.45.  What 
are the
 > new concepts that let you avoid the constant?

Whatever concepts are used it must indirectly be a question of
improved move ordering. The better the move ordering, the smaller the
need to do exploration.

 > Is it RAVE, because the information gathered during the search lets you
 > focus the search accurately without the UCT term?  Many people have said
 > that RAVE has no benefit for them.
 >
 > Do most of the strongest programs use RAVE?  I think from Crazystone's
 > papers, that it does not use RAVE.  Gnugomc does not use rave.

I've never had success with RAVE but I might make a new attempt for
GNU Go some time.

 > Is it the prior values from go knowledge, like opening books, reading
 > tactics before the search etc?  Do all of the top programs have opening
 > books now?  I know mogo does.

The MonteGNU account on CGOS (9x9) has a self-learnt opening book with
currently slightly more than 16000 moves. Over the last 1000 games it
has played on average 4 moves (own moves that is, opponent moves not
counted) from the book. The record is 22 moves from book.

 > Do most of the top programs read tactics before the search?  I know Aya
 > does.

GNU Go in Monte Carlo mode reads lots of tactics before the MC search.
But it doesn't use the tactics for the MC search. :-/

 > Does it matter how prior values are used to guide the search?  I 
think mogo
 > uses prior knowledge to initialize the RAVE values.  Do other programs
 > include it some other way, by initializing the FPU value, or by 
initializing
 > the UCT visits and confidence, or some extra, "prior" term in the 
equation?
 >
 > Are there other techniques (not RAVE) that people are using to get
 > information from the search to guide the move ordering?  I think 
crazystone
 > estimates ownership of each point and uses it to set prior values in some
 > way.

GNU Go uses a global move ordering shared by all nodes in the tree and
initialized from the results of the normal move generation.

/Gunnar