Author: Will Singleton
Date: 14:59:56 12/26/98
Go up one level in this thread
On December 26, 1998 at 11:00:31, Inmann Werner wrote: >On December 23, 1998 at 19:57:54, Roberto Waldteufel wrote: > >> >>On December 23, 1998 at 19:27:34, Inmann Werner wrote: >>> >>>I use Null move only in the "normal" alpha-beta (not in q-search) >>>I do it in each (nearly each) position before trying any other move. After doing >>>the null move I call normal alpha beta, but with less depth. There again can >>>occur Nullmoves, but never allow 2 in a row. When I get back my value, and it is >>>>= beta I stop this tree and return beta without trying any move. This reduces >>>the tree a lot. (But is not a really sure thing, but wrking fine.) >>>Second, if the value is rather deep (nearly mate) I extend the search with one >>>ply, cause there anywhere is a mate threat possible. Works also fine. >>> >>>Dont forget: Beware of Zugzwang!! >>> >>>Wish a happy Christmas >>> >>>Werner >> >>Hi Werner, >> >>Most of what you describe is the same as what I do, but I am interested to read >>that you allow multiple null moves in the same line. I only allow one null move >>in a line, which I implement by setting a flag after a null move that prohibits >>further null moves in all descendant nodes. Have you compared the two methods >>and found multiple null moves faster? Are null move related errors noticeably >>more or less frequent with multiple null moves? >> >>Also, can you explain exactly how you use the null move score to trigger an >>extension? Do you mean that you do this if the null move score is close to >>"giving mate" or when it is close to "being mated" for the side to move? >> >I must explain: > When white does a Null move, black has two moves in row. Now white gets back a >value lower -20000 (white gets mated, bad for white), I extend, cause there may >be a bad threat. It reall works fine. Example is the testposition LCTCMB01. With >this, Inmichess finds the good move in ply 6. Without in ply 8. It mostly works >fine together with allowed check extensions to find "nice" moves early. >I do not understand it really. Also I only check, if something goes really bad, >the program finds something really good much earlier. > >>And zugzwang, the great danger for null move. I dissallow null moves when either >>side has less than 3 pieces (not pawns). How do you do it? >> >I do it the hard way. As long as both sides have one piece (withou pawns) I >allow it. Maybe a little risky? > >>Merry Christmas, >>Roberto > >It is nice, that my answer helped you. Good to give a little back to you, who >often helped me a lot. :) > >Merry Christmas >Werner I will have to try the null-move mate extension. Was that an idea of Bruce's, originally? I only allow one null move in a search, like Roberto. I know multiple nulls are possible, but I never found much benefit in the idea. I suppose that's because, in blitz games, there's not much opportunity to do multiple nulls. I only get like 6-7 ply in the middlegame, so there's really no opportunity. Have you done tests that show a definite benefit to multiple nulls? Will
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