Author: Sune Fischer
Date: 05:29:44 12/06/01
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On December 06, 2001 at 08:12:22, David Rasmussen wrote: >>Perhaps your hashing scheme _is_ the problem, maybe that is why my results are >>better. >> > >Perhaps it is. Talk about that to Hyatt. It's his program. Ok, well its not so strange you have the same collision rates then. >Anyway, I think you need not worry about me understanding the math. After all, I >study math. I know of the birthday problem. It's not necesarily relevant here. Okay, then try and calculate the odds of getting 300 collisions out of 10000 using "danish: tilbagelægning" from a pool of 4 billion, those odds are astronomically small for sure, so something strange _is_ happening. >Sequences of chess positions following the chess rules are not random. They have >redundancy. No, but even if the positions are very similar the keys should be vastly different, this is also one of the ideas of using the zobrist table. >I don't. This is not hard evidence. This is theory based on false assumptions >and a wrong model. Feel free to name 1! :) >Hard evidence is hundreds (or thousands or millions if you >want) of pairs of positions that has the same pawn hash signature in Crafty. >That is by definition a collision. Maybe so, but you think you are proving that 32 bit keys are no good, when all you are proving is that you have _some_ bug IMO. >Could there be a problem with Bob's random >numbers? Sure, but I doubt it. Also, when we talked about a 32-bit hashing >scheme we both meant a "simple" one. That is, one where you generate random >numbers, not one where you handpick every number. Surely there is some linear og >non-linear algebraic code of high dimension that will have fewer collisions than >"good" random numbers, but, we were talking about random numbers, which is what >"people" use. Hyatt admits it is not good enough. I would like to see Bruce do a >similar experiment. Me too, espicially since it was him who talked Bob into it in the first place;) But you've seen my results and they confirm "my theory", so that would be a very strange double bug in any case. >Talk to Hyatt about that. As for me, I have tried many different PRNG's. All >with similar results. It is very strange indeed, but 32 bit seems to be working for me (for what ever reason), so I will change from 64 to 32 soon :) -S.
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