Author: Gerd Isenberg
Date: 11:05:48 12/03/05
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On December 03, 2005 at 11:56:42, Andreas Guettinger wrote: >On December 03, 2005 at 11:01:46, Paul Jacobean Sacral wrote: > >>I would appreciate a couple of clarifying remarks as well, because this is a >>topic that's difficult to understand if you are not a progammer. Bacically, I >>was studying explanations of this in the past but didnt't understand all of it, >>and also do not remember all of it. >> >>My question is: >> >>How come that some solving times of test positions are worse (longer) with >>bigger hash tables, than with smaller hash tables? >> >>Yours truly Paul J. Sacral > >Can you give an example? >The size of the hashtable should not make a considerable difference in solving >time, except if the engine clears the hashtable in analysis mode at the >beginning of the search, which could take 1 or 2s on slow hardware. (Note during >normal gameplay hastables usually don't get cleared.) >Per position (in the search tree) it takes normally 1 (written ONE) probe per >hashtable, doesn't matter if the hashtable is 1Mb or 1Gb. >As a banal example, if you have a file register in your office, and you want to >lookup file no. 56, it doesn't mater if you have 100 or 1000 files stored, you >just walk to the shelf and take file number 56. > >regards >Andy With changed table size you obviously map positions to other entries due to hasIndex ::= someHashkey % tablesize. Two positions with disjoint slots with some table size may share one slot with a bigger hash size. This is enough to explain completely different search behaviour - and for some patological cases even a longer solving time. Gerd
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