Darren Cook wrote:
Hi Jason,
In UCT the monte carlo searches (I find it clearer to call them "the
playouts") are always run to the end of the game. So they always
accurately (well, as accurate as a random playout can be!) take sente in
account. Therefore my understanding is that it does not matter whether
they start at an even or odd ply in the UCT part of the tree.
Darren
Let's take a basic example of a leaf node in an MC search tree that
hasn't been expanded, but has 4 children. Let's say that random
simulation through the children have winning percentages of {46%, 51%,
47%, 48%}. Assuming a uniform simulation policy, the winning percentage
would be the average of the four, or 48%... but when that node gets
expanded, it'll start discovering the winning percentages of the
children nodes. Now when we look at the node that used to be our leaf
node and ask what it's winning percentage would be, we come to a
different conclusion... The winning percentage is either 46% or 51%
depending on if the color to move.
In this example, the difference between the 0-ply and the 1-play is 3%
(51%-48%) or 2% (48%-46%) depending on what the color to move was. Does
that help?
Jason House wrote:
For simplicities sake, let's say I do a pure 0-ply and 1-ply monte carlo
search. If the color to move is my color, I'd expect the 0-ply search to
give me a more conservative winning percentage than the 1-ply search (since
I'd pick the best child rather than average the children together).
Similarly, if the color to move is the enemy color, I'd expect the 0-ply
results to be optimistic relative to the 1-ply results.
From what I understand of how everyone does UCT, the depth of leaves
are not the same and percentages are compared anyway. ...
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