Author: Sune Fischer
Date: 02:34:56 09/26/01
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On September 25, 2001 at 20:11:57, Robert Hyatt wrote: >>>That is correct. But the way zobrist works, it is far more likely that >>>that position is a _real_ match rather than a false match... So that once >>>you fill the table, you can't assume that _every_ probe from that point >>>forward is a false match. very few will be in fact... >> >>Well no, see my other post: >>http://www.icdchess.com/forums/1/message.shtml?190349 >>You forget that the problem here is, that you would not >>be able to update any entries, and so as the game evolves, new positions will >>occur and old ones will never be re-seached. This will lead to collisions. > >You overlook that positions get overwritten _all_ the time in the search. This >is a two-way street. They get overwritten. They get reused. They will, on >occasion, get incorrectly reused (collisions). But once it is full, the table >is not just "full". It will still get overwritten furiously because of all the >shallow leaf searches that demand to store information in the table... Yes so true, but if your table is twice as big, then you have twice as many entries to overwrite, the likelihood of you missing one that eventually ends up as a collision is therefor greater. And as you increase the size of the table, the average "age" of each hash element will also increase and thus diminishing the chance of a good clean hit. >IE I don't believe that doubling the hash size will double that collision >rate. But that I can test when I have some time. It will be interesting to >try. I might get time on a machine with 16 gigs of RAM so I can try doubling >several times to see what happens. Good idea, but you might want to use smaller keys, or you will have to let it run forever to get a good statistic. Thank you for the clear answer BTW, we disagree then, no harm in that :)
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