Author: Richard Pijl
Date: 23:51:55 09/21/04
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On September 21, 2004 at 19:44:00, Stuart Cracraft wrote: >On September 21, 2004 at 18:01:26, Richard Pijl wrote: > >>On September 21, 2004 at 17:36:47, Stuart Cracraft wrote: >> >>>Hi -- this past weekend I switched from single-tier replace >>>always to two-tier place 1st tier in 2nd if incoming position >>>is searched to a >= depth than currently stored at hash entry >>>and store incoming position in 1st tier, otherwise always replace >>>2nd tier if depth is. >>> >>>This is represented by the actual code below. >>> >>>After doing this, I expected least the same result or slightly >>>better (than 250/300 on Win-at-Chess). Instead I scored 248/300 >>>(consistently) with Two-Tier and 250/300 consistently with One-Tier. >>> >>>I am asking that some of the talented folks look this over >>>and tell me if this is grossly wrong (expectation -or- code.) >>> >>>Or what might be the best methods for evaluating the function of >>>the two methods... >>> >> >>Replacement schemes start making a difference when entries start to get >>overwritten on a regular basis. So, don't expect a big difference on 1 second >>searches. The overhead of a dual probe (without looking at your code) may hurt >>at such short searches. >>What you can do is reduce the hash size to, lets say 10kb and then compare >>scores again. >>Richard. > >I always wondered why aging of entries in the hash table using a timestamp >wouldn't be better. > >Stuart I'm not sure what you mean here. Do you mean using aging of entries vs clearing the hashtable between moves? In the Baron I'm doing aging. The only reason I can find not to do this is because the differences in distance to root of the search positions may cause instability (e.g. because of preprocessing, distance to root dependent extension limitations and pruning, etc.). I see no reason not to use old entries for e.g. moveordering though. Richard.
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