Re: [gnubg] Help with a new MET (2)

[Timothy Y. Chow]

Ian,

The topic of "fish METs" is an interesting one.  I think that they can be 
useful for non-contact race cubes, where humans can make precise 
calculations over the board using race formulas.  Beyond that, I'm a 
little skeptical about how practical they are.

One thing that I feel that hardly anyone pays attention to is the fact 
that two players with the same PR can have very different styles and make 
very different kinds of mistakes.  In today's PR-crazed world, there is a 
strong tendency for most people to oversimplify and use just one number to 
capture a player's backgammon ability.  In reality, backgammon ability is 
a multi-dimensional beast.  In my own playing group, I know that one 
player plays blitzes much too timidly, while another plays blitzes well 
but has a strong tendency to break anchor too riskily.  When I'm playing 
one of these players and am assessing taking a blitz cube or offering a 
holding game cube, I will definitely take into account my knowledge of 
their individual playing weaknesses.  It's quite possible that both 
players have the same PR, in which case a fish MET might not distinguish 
between them.

The fact that backgammon ability is multi-dimensional means that it's hard 
to create credible fish METs with any degree of accuracy.  If one tries to 
cripple GNU by forcing it to make occasional random mistakes, one can 
measure the PR of "crippled GNU", but this does not mean that crippled GNU 
is a credible model of how a human (with the same PR as crippled GNU) 
plays.

The Jacobs/Trice fish book is a wonderful book and an interesting proof of 
concept, but I think that the above difficulties (among others) mean that 
it's hard to actually apply the ideas in real life.

Tim