Quoting Michael Williams <[EMAIL PROTECTED]>:
Magnus Persson wrote:
Yesterday I noticed an odd phenomena in Valkyria wich was caused by
high selectivity and AMAF.
Then since there is nothing in the AMAF scores that indicate that
move 2 is any good it is never searched, since the search is so
selective that the bounds will not grow large to compensate for the
bias in a reasonable time.
Isn't this fixed by never straying from a move in the tree until it
loses and then trying an untried move?
Or something like that. It wasn't my idea and I don't remember the
details, but it seems like it fixes what you describe.
No, it does not because the AMAF score for move 2 is strictly lower
than the evaluation for move 1 and all other moves for some reason. It
will try other moves deeper in the tree instead and the position is
sufficently complex to generate a very large tree until it gives up on
the move at the root level. The thing is that if it searches move 2
for at least 100 simulations it will discover it is a good move. But
because of the AMAF score is so low and all other moves are indeed
losing moves it sticks to move 1 because it at least makes it into a
fight although at bad odds.
Otherwise I am quite happy with the current implementation since it is
strong in testing, this only happens when there are two hot candidates
and the first one is searched first because of a limitation in move
ordering, and a particularly strong bias works against the second best.
The annoying thing is that is can suddenly lose a game it was winning.
But I found a better fix. I also tried to enter my pattern priorities
as the priors of the AMAF scores. And I now strongly believe that this
is also better in general and not for this particular situation. In
the position I wrote about yesterday this version get the right move
almost immediately. I tested as Valkyria 3.2.0 overnight on CGOS and
it seems to be just as strong as the previous version, and I can still
tune the parameters of it.
This means that the search of position will be guided in order by
1) My pattern priorities disguised as priors of AMAF scores.
2) Then AMAF score will take over
3) If a move is searched, then the true winrates for those moves will
be used and there is no bias from the pattern priorities except very
weakly from the AMAF scores.
-Magnus
--
Magnus Persson
Berlin, Germany
_______________________________________________
computer-go mailing list
computer-go@computer-go.org
http://www.computer-go.org/mailman/listinfo/computer-go/
