Author: Dan Newman
Date: 12:54:28 09/23/98
Go up one level in this thread
On September 23, 1998 at 15:14:58, John Coffey wrote: >On September 22, 1998 at 22:37:24, Dave Gomboc wrote: > >>On September 21, 1998 at 18:35:42, John Coffey wrote: >> >>> >>>>I try them _everywhere_ in the search, before trying any other move. The idea >>>>is that if your opponent can't take two moves in a row and crush you, your >>>>position is **overwhelming** and doesn't need any further searching to prove that >>>>it is probably winning... >>> >>>The "**" above are mine. >>> >>>So you only try them when ahead in material? I just needed to clarify >>>that because you also say "everywhere." >>> >>>Thanks a lot. >>> >>>John Coffey >> >>He really means **everywhere**. Actually, he might disable them in a few >>low-material endgame positions if tablebases aren't present. Or he might not. >>:) >> >>But yeah, basically **everywhere**. >> >>Dave Gomboc > > >What is confusing to me is that I thought that null-move search is only done >when ahead in material? Why do them when the material is even or when one >is behind in material? > >John Coffey Just because you're behind in material at a node, doesn't mean you won't regain (some of) it in the search below that node. Let's imagine that at a node you are behind in material, but are just about to deliver mate, and your opponent can't get out of it--even if he's given two moves in a row. The null move will return the mate score and give you an instant cutoff. Or imagine the oppenent can get out of it with those two moves, but only at the loss of a lot of material. Again you might get a cutoff. The null move works as long as the score returned by the null move search is greater than or equal to beta. What the current material is is...immaterial. -Dan.
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