Author: Gerd Isenberg
Date: 14:06:29 04/29/04
Go up one level in this thread
On April 29, 2004 at 16:03:08, Robert Hyatt wrote: >On April 29, 2004 at 02:08:40, Tony Werten wrote: > >>On April 28, 2004 at 16:14:39, Gerd Isenberg wrote: >> >>>On April 28, 2004 at 13:45:05, Ed Schröder wrote: >>> >>><snip> >>> >>>>What is double nullmove? I only know recursive nullmove allowing multiple >>>>nullmoves. I also read about "allowing 2 nullmoves in a row". What are the >>>>differences? >>>> >>>>I use recursive nullmove, not allowing the next ply after the nullmove to >>>>nullmove. So: >>>> >>>> e2-e4 >>>> e7-e5 >>>> **-** // nullmove >>>> d7-d5 // do no allow nullmove >>>> >>>>When I remove that check I get a few percent speedup, results look okay. >>>> >>>>Ed >>> >>> >>>Hi Ed, >>> >>>yes Double Nullmove, suggested and invented by Vincent, allows to play two >>>nullmoves in a row, to efficiently get rid of zugzwang problems. It is recursive >>>too, and if i understand correctly, it works fine without any nullmove >>>precondition: >>> >>> if (!inCheck) >>> { >>> if ( move2thisNode != null || move2ParentNode != null ) ( >>> val = -doNullMoveSearch(depth-1-R,...); >>> if ( val >= beta ) return val; // return beta; >>> } >>> } >>> >>>May be Vincent may correct me. >>>It seems that there is an implicit kind of IID with 2R-2 too. >> >>Correct. Chech your hashtable again after the nullmove, if you didn't have a >>best move before. >> >>Then throw out IID. >> >>Tony > >I don't see how/why one would throw out IID. > Yes but with double nullmove you may search a line like that, eg. for a 12ply search: null null e4 e5 Nf3 Nc6 Bb5 a6 .... which is IMHO a kind of IID with depth-6, so if you store hash after null null with best found e4, and probe after after nullmove, it is likely to get a hit. Or? >NULL can collapse search to q-search, which means the best you can hope for is a >capture should you search this position later. That's not the same as a "good" >move when depth>0. If you mean after the second null, you are now 8 plies short >of a full search, which in most middlegame positions is going to be into the >capture only search... >
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