Author: Andrew Williams
Date: 02:37:06 08/10/01
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On August 10, 2001 at 04:30:20, José Carlos wrote: > After completely rewriting my chess program (Averno), I've run into the >null-move world, which I haddn't in old versions. > In old Averno I had: > > -Reasonably good move ordering (hash move; good captures; killers; ...) > -Transposition table > -2 killers > -Lazy eval > -Check and recapture extension > -Some out-of-check stuff in qsearch > > With that, I was searching 6-7 plies in blitz (in midgame) and 7-9 in >standard. [Athlon 550] > > I've read some open source programs to get a clue on how to search deeper, and >now I have: > > -Nullmove (tried R=3 and R=2, not yet R=2/3) > -Futility pruning > -Same move ordering as before > -Same hashing scheme > -Same 2 killers > -Same Lazy eval > -Check and null-threat extension > -No out-of-check stuff in qsearch > > And now, I search 7-8 plies in blitz and 8-10 in standard (and the worst thing >is that the program looks weaker than the old one!) > That looks like a poor search depth, isn't it? So what am I missing to get, as >most null-movers, 12-13 in standard? > SEE? History heuristic for move ordering? ETC? Razoring? > Sorry for _answering_ instead of _trying_ but, as I have so little free time >to work on my program, any advice would be appreciated. > As well, I'd like to know if, with the stuff I've implemented so far, I should >expect a better performance. In that case, I might have a bug somewhere. > > Thanks in advance, > > José C. Seriously, I think the first thing you should look at is move-ordering. I find that errors I introduce here have an enormous impact on the depth of searches. One metric that many people use is to see what proportion of beta cut-offs in the search are achieved on the *first* move searched at a given node. The higher this figure the better. Aim for over 90%. Cheers Andrew
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