During the main search, pass is always one of the moves searched, and if is the best move found, and pass is allowed, it will play a pass. I never avoid searching "pass" in the main search since it gives a good lower bound on the score. If the search returns "pass" too early, I'll play the second best move instead.
Many Faces of Go uses the following rules: - pass is always allowed if the opponent passed on the previous move otherwise - pass is allowed if the move number is at least half the board size (181 on a full size board) and the pass search found no good moves for the opponent. Before I do the main search for the color to move, I do a pass search for the opponent, to find good opponent moves if the color to move passes. These moves are searched early in the main search. I'm trying to find killer moves early. David > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Don Dailey > Sent: Sunday, October 22, 2006 5:08 PM > To: computer-go > Subject: Re: [computer-go] When is Pass the best move? > > > I'm in a similar situation, I'm trying to identify classes > of moves that I can eliminate in an admissible way - which > means the move I am throwing out is either not the best move, > or there are other equally good moves. > > I know that pass moves can be the best move in seki situations - and > it's non-trivial how to identify them. > > I'm not good at go and this is a severe handicap for me, but > here is what I come up with so far - please add to my list if > you know of anything else: > > 1. Benson space - I use benson's algorithm to find > pass-alive groups > and if a small "region" is enclosed completely by benson > groups, there is never a point moving inside of them for either > color (except in cleanup situations for Chinese rules) > > A "region" is defined as strings of points that can consist of > any combination of enemy stones and empty intersections. > > A large region can exist inside benson safe groups that allows > for life - so care must be taken that you identify the correct > regions. I don't know if I'm doing it the most efficient way, > but I'm going by region size. A region of 7 inside a benson > group cannot possibly support enemy life. So moves inside them > by either color do not improve the position. > > 2. I have a quick and dirty pass rule - I throw out all pass moves > in the early part of the game. I can't prove this rule is > admissible but I feel very safe with a rule like, "don't allow > pass if half the points on the board are empty." > > I feel you can probably be a lot less conservative - > but if anyone > knows a way to identify when to start including pass moves in a > search in a theoretically sound way - I'm all ears! > > 3. Unfortunately, the eye-filling rule is not admissible other than > in benson situations. The eye-filling rule I use has been > described on this group - don't move to a point surrounded on > all sides by stones of the same color - where the opponent > doesn't occupy more than 1 diagonal (different if on edge of > board.) I may or may not use this rule depending on what I'm > trying to do. > > 4. Don't move to any of the corner points on the first move. > > > Right not I'm working on a perfect solver for 5x5 - and rule > 1 and 2 are > the only rules I know that are 100% admissible. I suspect > rules 2 and > 4 are admissible - at least on 5x5 or larger although I > cannot back that > up with any theory. > > Rule 4, the corner rule can probably be generalized - and I > think that's > what a good pattern database might be able to do. I would > like to be > able to build an admissible pattern database of the form that veto's > specific moves. But the database must be provably correct, > not built > based on a humans intuition that a move is "probably" not good. > > So I'm basically lost here. my solver is just a step > towards the goal > of a pattern database that can admissibly remove many > pointless moves from a tree search. > > > - Don > > > > > > On Sun, 2006-10-22 at 10:47 -0700, Phil G wrote: > > Does anyone have an example where "pass" is the best move, and not > > part of the two passes to end the game? I'm trying to determine if > > passes should ever be considered in a search for the best > move, and if > > so, how to exclude them until it is really necessary. > > > > > > > > Thanks, > > > > > > > > Phil > > > > > > > > > > _______________________________________________ > > computer-go mailing list > > computer-go@computer-go.org > > http://www.computer-go.org/mailman/listinfo/computer-go/ > > _______________________________________________ > computer-go mailing list > computer-go@computer-go.org > http://www.computer-go.org/mailman/listinfo/computer-go/ > _______________________________________________ computer-go mailing list computer-go@computer-go.org http://www.computer-go.org/mailman/listinfo/computer-go/
