Author: Sune Fischer
Date: 06:44:44 12/05/01
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On December 05, 2001 at 09:17:39, David Rasmussen wrote: >That's all true. But I'm not asking "why doesn't this work". I am assuming that >people think that 32-bits is ok for chess, and I'm indeed asking "are you sure >that there isn't a problem with this, such as hitting too many different >positions for this to be a good idea, because I am seeing collisions". And I am saying, that _if_ you get collisions then that is most likely a problem, but I don't understand why you are getting collisions at all in the first place. >Sure, but that would be a little harder to implement than the experiment I'm >doing now. The important thing is that we want to be able to actually tell >different positions apart. I have now rerun the experiment but with the change >that I also check some of the data that is stored in the table, that is _not_ >dependant on anything (such as asymmetry og game phase) other than the pawn >structure itself (such as the 8-bit bitboards of which files contain white >pawns, likewise for black pawns, the 8-bit bitboards of files with passed >pawns). And the collision rate is the same. This test is even stronger, as it >positively says that the position that was hashed here was definately not the >same position as this one, because they have pawns on different files. The rate >seems to be exactly the same, and as I felt pretty sure that I had accounted for >asymmetries and gamephases in the first place, this new experiment only confirms >that. We need Bob or some other third party to make tests too I think. >If there _are_ collisions, those 10000 positions (if that is even a reasonable >number, I assume it is), are getting overwritten pretty often. >So why don't you >believe that this is what is happening? Why would they get overridden? Most of them will fit in a small table, and since there are no more positions there is nothing else to collide with. >/David
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