[Computer-go] issues on 19x19

Petr Baudis pasky at ucw.cz
Wed Apr 27 11:10:51 PDT 2011


On Wed, Apr 27, 2011 at 11:23:41AM -0400, Daniel Shawul wrote:
> 2) My second problem concerns use of progressive widening/unpruning which
> looks like a must to have on 19x19.
> The problem I have is with the move ordering... If I tell it to  moves on
> the 3rd line from the edge are good ones,
> it continually puts its stones on that line (hence forming a square), while
> the opponent controls the centre and also
> cuts some parts of the 3rd line.
> Then I used fillboard to try and fix this issue, but the engine once again
> tends to prefer these moves and put stones
> all over the board. Which is when I realized it is impossible to fix it with
> static move ordering.
> Should I use something dynamic like RAVE to order the moves? That will be
> inconvinient  because I order the nodes
> only during first allocation.
> Also the default progressive unpruning formula seems to select too few moves
> for consideration, so I had to add 20 additional moves
> to make it work for my engine.

  You should explain in more detail exactly what you are doing right
now, as the terminology is highly muddled. I assume that now, in n-th
tree descent through given node, you consider only f(n) children for
next move instead of all children. Also, I assume you use just plain UCT
for node evaluation?

  I think progressive bias (considering all children, but giving extra
bonuses to values of some or all children) is much better explored
approach (at least in literature). However, it's certain that just using
a single criterion for the ordering is not going to work well. You can
either use a mix of patterns, hints from some other engine, or (best)
RAVE values. Plus some extra coefficients for tactical checks (e.g.
atari), last move CFG-distance and distance from edge.

  I think you will find it very difficult to achieve reasonable
performance on 19x19 without RAVE. But if you are reluctant to do that
yet, at least try combining last move CFG-distance, distance from edge,
basic tactics and Mogo 3x3 patterns. The larger the mix, the more
diverse your array of considered moves will be. In particular, I have
found last move CFG-distance to be immensely important for gaining
strength on 19x19.

				Petr "Pasky" Baudis
UNIX is user friendly, it's just picky about who its friends are.

More information about the Computer-go mailing list