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BGonline.org Forums
Rollout
Posted By: Matt Cohn-Geier In Response To: Rollout (Michael Klein)
Date: Monday, 29 December 2008, at 9:27 p.m.
Here's the deal with truncation: the advantage is that the games will go faster since they only have to go X plies deep instead of until the end of game, and the rollout will take less games to reach significance. So it will speed things up considerably which is a concern if you have a slower computer. The disadvantage is that the rollout will be less accurate and often won't correct errors in the evaluation since the game terminates with a GNU evaluation rather than a result.
On cube decisions truncation can be a problem since evals are very often not good for absolute equities. However, evals will tend to be pretty good for relative equities. Since cube decisions are based largely on GNU's evaluation of the absolute equity of the position but checker plays are not, it isn't bad for checker play decisions.
The odd-ply vs. even-ply thing: sometimes you will get weird results when you truncate even-ply rollouts at odd plies deep (e.g., you did a 2-ply rollout truncated at depth 11). If you're going to use truncation and do a 2-ply rollout it should be truncated at depth 10 or depth 12 (or depth 2X).
I generally prefer to do full (non-truncated rollouts) since they are more accurate and speed isn't a big concern with computers these days. However, if you are using old/slow hardware, you may want to use some setting that makes the rollout run faster--truncation, stepped, 0-ply, whatever.
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