[Bug-gnubg] Analysis of race rollouts

[Ian Shaw]

I've just had  a look at Joseph's analysis of race rollouts. I've got a bunch 
of questions, but I'm short on answers.
If I understand the numbers correctly, 2-ply evaluation produces less errors 
than the one sided bearoff database (OSRDB). How can this be? One would 
instinctively think that the OSRDB would be most accurate.
As Joseph notes, the rollout might be wrong. With 97507 positions, we can 
expect some of them to produce results outside the 95% CI. Would comparing the 
rollout to Sconyers' or Trice's databases prove anything?
The OSRDB might be wrong in positions where two sided database might get it 
right. E.g. desperate situations where you need to play to take advantage of 
specific doubles. I guess it's not surprising if 2-ply gets some of these but 
OSRDB can't. Is it possible to find the error rate for OSRDB supplemented by 
the two sided database when the position falls within the scope of the latter?
Jørn's been slaving away at extending the OSRDB, but are we getting anything 
extra from it if 2-ply is just as good/better?
Is there any value to comparing 3 or 4-ply results with the rollouts? I'd be 
prepared to give some PC time to this if it would help.

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Ian Shaw