Author: Vincent Diepeveen
Date: 13:43:08 08/10/01
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On August 10, 2001 at 10:28:03, José Carlos wrote: Be aware to correctly reduce depth with nullmove. at depth == 5 ply left with R=3 you should search 1 ply for the other side when nullmoving. The number of bugs might be gigantic. For example a bug i had one day was move repetition. After a nullmove Diep said: "he cool i've got this position more than 1 time so this is a draw". It was in short not stopping the check for repetition when nullmoving. Another load of bugs are possible, also important is hashtable. the better and more bugfree your hashtables are, the better nullmove will work. At least 2 probes is what i advice! >On August 10, 2001 at 09:51:39, Robert Hyatt wrote: > >>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? >> >>Are you sure you have implemented null-move correctly? IE R=2 everywhere, >>trying null-moves _everywhere_ (except for not allowing two consecutive null- >>moves in a row)? Allowing multiple null-moves in a single path with the above >>restriction? >> >>You should be going deeper. Significantly deeper. > > That's what I expected to hear... :( > Yes, I'm trying null moves everywhere, except two consecutive and when >inCheck. I must be doing something wrong. I'll check my move ordering and null >move implementation, but the look fine, at first sight. > Anyway, thanks for your help. > > José C.
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