Author: Ed Schröder
Date: 11:17:49 07/25/00
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On July 25, 2000 at 12:32:59, Graham Laight wrote: >On July 25, 2000 at 10:30:01, Ed Schröder wrote: > >>On July 25, 2000 at 06:55:22, Graham Laight wrote: >> >>>On July 25, 2000 at 01:58:54, Ed Schröder wrote: >>> >>>> >>>>Hash tables and NPS generally have very little in common. Lowering the >>>>hash table size will increase NPS with a few percent because less hash >>>>table code is executed. >>>> >>>>Ed >>> >>>If this is right, then the best thing to do is to have no hash tables whatsoever >>>- this will maximise your NPS and simplify your code! >> >>No hash tables will result in a speed drop of a factor 3-4 average. The >>hash table code is in the search module and not in the evaluation module. >> >>Ed > >Sorry, but I'm getting confused here. Let me try to state as simply as possible >what I think you're saying, and if it's wrong, somebody can correct me: > >* hash tables are used to store positions which have already been evaluated > >* sometimes, in the search, a position will come up which has already been >looked at previously > >* if so, that branch of the search need not be done again, because the results >are already in the hash table > >* thus, using hash tables, you'll do fewer NPS, but you'll still be better off >because you won't be wasting time searching branches that have already been >searched > >-g The increase of NPS with no hash table explains as follows: - less code to execute for the processor. - no waste of the PC's data cache. The bigger the hash table the more worse for the L1 data cache. Not that it matters we are only talking on a few percent here while the gain in speed is about 300-400 percent. Ed
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