Author: Bernd Nürnberger
Date: 04:45:19 04/01/04
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Hello Pat, On March 31, 2004 at 19:49:22, Pat King wrote: >On March 31, 2004 at 07:43:59, Bernd Nürnberger wrote: > >>(1) >>[3 moves] >> 8. 0:01.12 993512 0.00 Nc3 Nf6 d4 d5 Nf3 Bf5 Ne5 Ne4 >>[4 moves] >> 8. 0:01.28 1088694 0.00 e4 Nc6 Nf3 e5 d4 Nxd4 Nxd4 h6 > >When you say "3 history moves" and "4 history moves", I'm interpreting this as >"I sort the first three or four quiet moves using the history table". I have two >thoughts. Yes, you got what I meant. Sorry for not putting this more clearly. > >a) I sort all quiet moves by the history table. It's probably a waste, but it's >simpler. Doing this strangely I get even more nodes (and still another different PV) on the starting position: 8. 0:01.38 1169525 0.00 d4 Nc6 e4 d5 exd5 Qxd5 Nf3 Be6 (?!) Why does the amount of nodes go up, when the ordering should be better? I am aware of that the heuristic is just a prediction that do not have to be true, but should the prediction not be more accurate? What parameters for increasing score (+ 1<<depth) and aging (at 64k nodes do /8 on all from-to pairs) do you propose? >b) If I chose to limit my sorting (which quite probably is a good idea) I >wouldn't make decisions based on the starting position. Very few (I would say >"no", but I always get in trouble with absolutes) chess engines are any good at >openings with a pre-made "book". That was just an example to illustrate. Propably the starting pos. is a bad test pos., but I also tested other positions ... >The two lines you present are not unreasonable for a chess engine with no book. But is it reasonable that they are so much different for just sorting *one* more move by history score. It varies very widely when altering move ordering! Is this ok? > >> >>(2) >>[move ordering] >You mention that you've implemented null move. I believe the proper place to put >this is before even your hash move. This could seriously impact your cut rate. >If you're not counting null move cutoffs as 'cuts', then I think you may have an >apple and orange type problem when you compare yourself to other engines. Strangly this do not change anything in my engine. Will try this more thourougly when I have more time. But why do the null move before hash table lookup. Isn't it cheaper to place it after the hash lookup, because if I got a hit (and I often got hits), null move will not be examined at all?! >Glad to shed what feeble light I have on your problems :) :) Greets, Bernd
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