I have made some minor performance improvements and this is as far as
I intend to take this particular project. I might make some small
changes if necessary, but most likely I'll leave this largely
unchanged from now.
I had set myself as an arbitrary goal that it should do at least 20K
playouts. But with real liberties, AMAF and a RAVE formula I got
stuck in the 16K-17K range. According to my profiler that is mostly
due to the expensive formula used to compare nodes, where it says it
spends 25% of total time. The formula I'm using is:
beta * (virtual-win-ratio + RAVE) + (1-beta) * (win-ratio + UCT)
beta = 1 - log(parent-visits) / 20
UCT = exploration-factor *sqrt( log(parent-visits) / (nr-visits+1) )
RAVE = exploration-factor *sqrt( log(parent-visits) / (nr-virtual-
visits+1) )
There are probably quite a few possibilities still to tune this
program with regards to playing strength and performance. But I felt
it doesn't help to obscure the implementation by too many details.
The implementation of the search algorithm was entirely game-
independent, until I introduced AMAF. I didn't see how to fix that,
as there's no way getting around that it's based on the fact that a
move is represented by a single coordinate, which is mapped to an
array to store the statistical values. But strip the AMAF part, which
is a block of 30 odd lines of code, and I think it can be used for
other games basically as-is. I did this not because I ever see myself
program another game, but because in my experience in doing so I get
a cleaner separation between modules.
At 2,000 playouts, it's still quite a bit weaker than the plain MC-
AMAF refbot. It wins only about 33%. But that's probably because the
1,000-2,000 playouts range is the sweet-spot for that particular type
of playing engine. It doesn't scale from there, whereas the MCTS ref-
bot only just gets warmed up with 2,000 playouts.
This leads me to a question. I suppose it might be of some interest
to put this bot up on CGOS. But what parameters to use? The main one
being the number of playouts, naturally.
Mark
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