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
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