Another thing about Zobrist hashes... after you select the canonical hash, you will end up with a non-uniform distribution. If this value is going to be used in binary tree, you may wish to swap the low-order bits with the high-order bits to keep the tree more balanced.
On Dec 19, 2007 10:44 AM, Don Dailey <[EMAIL PROTECTED]> wrote: > I actually have a routine in Lazarus that rotates a full board. It's > called transformBoard() and it takes 2 arguments - a board to rotate and > a transformation (0 through 7) and returns a new rotated board. > > I don't use it much except for debugging or stuff done at the root, > because there are faster ways to do things. > > I also have a routine called canHash() which returns a canonical hash > of the board by trying all 8 transformations and returning the lowest > valued one. It is more efficient (but not efficient) because it > doesn't actually produce a new board - it just builds 8 hashes of the > board from scratch without touching anything. This routine is only > used at the root for storing opening book moves. > > You can use zobrist hashing for maintaining all 8 keys incrementally, > but you probably need a fairly good reason to do so. Incrementally > updating of 1 key is almost free, but 8 might be noticeable if you are > doing it inside a tree search or play-outs. It depends on how "fat" or > "lean" your program is. Even 8 keys may not be noticeable if your > program does a lot of work at each move (or an end nodes.) If you are > not, then it doesn't really matter how you do it. > > I typically have 2 routines for everything - I have a slow_make() and a > fast_make() and the fast_make() doesn't care about superko (although it > checks for simple-ko) or anything that fast play-outs doesn't care > about. So the fast make doesn't even try to update zobrist keys. > > > - Don > > > > > > > Ben Lambrechts wrote: > > Hi all, > > > > I am planning a fuseki database. > > Now I got the following problem: how to rotate/mirror the board for a > > unique representation. > > > > $$c > > $$ +---------------------------------------+ > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . O . . . . . , . . . . . X . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . , . . . . . , . . . . . , . . . | > > $$ | . . . . . . . . . . . . . . . . 5 . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . O . . . . . , . . . . . , . . . | > > $$ | . . . . . . . . . . . . . . . X . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ +---------------------------------------+ > > > > $$c > > $$ +---------------------------------------+ > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . 5 . . . . . . . . . . | > > $$ | . . X , . . . . . , . . . . . X . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . , . . . . . , . . . . . , . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . O . . . . . , . . . . . O . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ | . . . . . . . . . . . . . . . . . . . | > > $$ +---------------------------------------+ > > > > Both are the same board, but has anyone made an algorithm that rotates > > the board or an area of the board in a unique way? > > I don't need the move order, just the "snapshot" of the board. > > > > Ben > > _______________________________________________ > > 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/
