Sorry for posting then, I didn't realize that it had been tried. I may work through the problem and try to get it to work in order to fully understand why it in fact does not work. If by some miracle I manage to get something working with a collision rate of 1/(2^61) I'll certainly post it. Thanks for the info.

- Nick On 2/9/07, Erik van der Werf <[EMAIL PROTECTED]> wrote:

Nick, The basic idea of what you're describing is well known. It was first published by Antti Huima several years ago. Unfortunately though, his implementation was flawed. I didn't check your code but likely it suffers from a similar defect. It is possible to fix the defects in Huima's scheme. If you ignore colour symmetry it's relatively easy to find a defect-free xor-based scheme that works with 8 segments. The more interesting part is in finding the minimal number of segments, and then proving correctness. Nic Schraudolph has done some interesting work on this, but as far as I know he still hasn't published it. Maybe if we all sit on him we can finally get him to finish it :-) Erik On 2/9/07, Nick Apperson <[EMAIL PROTECTED]> wrote: > Hey all, > > I was thinking about our conversation and i decided to design a zobrist > class that allows for easy comparison to check and see if 2 different > zobrist values are equivalent after a rotation etc... It updates the > zobrist in such a way that it can transform them and after trying 8 > possiblilities, it can determine if they are equal. There are actually > quite a few optimizations that could be performed on it, but I just wanted > to post the basic idea. See the following source code for the basic idea: > > http://www.nicholasapperson.com/computergo/zobrist.h > > Essentially it works so that it hashes the played stone as each of the > rotated forms and stores that in each of the 8 bytes used. The bytes are > arranged in an order such that flipping the 2 DWORDs results in the zobrist > value for if there was a rotation in the x axis, flipping WORDs results in a > reflection across the y axis and swapping bytes results in a reflection > across the y=x line. Order obviously matters in the case of xy so the > transformation is assumed to take place after the other reflections. For > example: > > if we have 0x1234567890ABCDEF as a zobrist value, > > 0x90ABCDEF12345678 would be the zobrist of the position with a reflection > across the x-axis > > > Anyway, I'm sure there is a bug or two, but I wanted to get your alls > thoughts. > > - Nick > _______________________________________________ > 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/

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