Re: [Bug-gnubg] Neural network symmetry question

[Mark Higgins]

Thx! Makes sense. Though I wonder if adding back in the "whose move is it" 
input and reducing the hidden->output weights by half ends up as a net benefit 
for training. Maybe I'll test it out. 



On Dec 10, 2011, at 2:06 PM, Frank Berger <address@hidden> wrote:

> Hi Mark,
> 
>> If I take a given board and translate the position into the inputs and then 
>> evaluate the network, it gives me a probability of win. If I then flip the 
>> board's perspective (ie white vs black) and do the same, I get another 
>> probability of win. Those two probabilities should sum to 1, since one or 
>> the other player must win (or equivalently, the probability of white winning 
>> = probability of black losing = 1 - probability of black winning).
> 
> 
> I assume your assumption is wrong. IIRC in an earlier paper there was an 
> input to indicate who's on. It is much simpler to present the position from 
> the point of the moving player, because the net has to learn less. I'm not 
> that familiar with the gnubg code, but I think they do it in this way, so you 
> can't just turn the perspective.
> 
> ciao
> Frank
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