Author: Andrew Williams
Date: 14:31:20 04/10/02
Go up one level in this thread
On April 10, 2002 at 15:28:26, Pat King wrote: >On April 09, 2002 at 12:11:08, Andrew Williams wrote: > >>On April 09, 2002 at 11:56:45, Pat King wrote: >> >>>On April 08, 2002 at 15:17:46, Robert Hyatt wrote: >>> >>>>How do you define "collision"? Normally this means two different board >>>>positions produce the same hash signature. If you are getting _those_ you >>>>have a Zobrist hashing bug. >>> >>>How do you detect collisions, then? Record the entire position in the hash >>>table? Even for a debug build, that seems like it would be impractical. >>Although undetected hash bugs are even less practical :) >>> >> >>You check to see if the move stored in the hash entry is legal or not. If >>the hash keys match but the move isn't legal in the position, it means that >>you have a hash collision. >> >>Andrew > >But you rely on the hashed positions being different enough for that move to be >illegal. Certainly, your technique detects collisions, but not all collisions!? > >Pat Yes. I should have been clearer. I don't have any code in PM to detect collisions. As you say, what I described wouldn't catch all collisions. Andrew
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