[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Bug-gnubg] Oddity/Bug in Rollouts?
From: |
Christian Anthon |
Subject: |
Re: [Bug-gnubg] Oddity/Bug in Rollouts? |
Date: |
Mon, 14 Apr 2008 12:56:38 +0200 |
This the odd/even ply problem at its worst. First of all the cube
action is strange because gnubg grossly mis-evaluates the position for
one or both sides. Look at Max' examples and I'm sure you can come up
with a reasonable explanation.
So, is it a bug in the code or in the net(s)? This is actually quite
easy to test in this particular case!
First of all set up the position and press ctrl-e (or select eval
under the analyse menu) and you get:
-----
Position ID: BwAAmG1bCkEAAA
Match ID: UQngARAAIAAA
Evaluator: CRASHED
Win W(g) W(bg) L(g) L(bg) Equity Cubeful
static: 0.653 0.000 0.000 0.002 0.000 +0.304 +0.495
-----
assuming that you evaluating at 0ply.
Next: I'm sure that we can all agree that it doesn't matter much what
X rolls next. So let's just give him a 62 played 19/11 (wrongly I'm
sure). Make sure that O is now on roll and eval the position again:
----
Position ID: tm2pCAAHAAAYAA
Match ID: EQHgARAAIAAA
Evaluator: CRASHED
Win W(g) W(bg) L(g) L(bg) Equity Cubeful
static: 0.185 0.003 0.001 0.000 0.000 -0.626 -0.866
-----
As you can see X's 0ply cubeless winning chances are 0.653, while the
1ply cubeless winning chances are 1.0-0.185 = 0.815 (under the
assumption that 19/11 is perfectly neutral).
So its in the nets.
Christian, gladly demonstrating when the eval function is a nice tool to have :)