Author: Andrew Platt
Date: 04:19:21 09/25/04
Go up one level in this thread
On September 25, 2004 at 06:35:57, martin fierz wrote: >4) i never thought much about verified 0-move pruning. but a post i read last >week made me think: i always thought i could do the following: > >if(pieces > 0) > if nullmove-fails-high > return value; >if(pieces == 0) // do a verification search > if nullmove-fails-high > verify result with a normal search with reduced depth. > if verification-search-fails-high > return value; The standard verification search doesn't have your condition above. It just says if it fails high, verify. >now there was this post saying that this won't work because you have to disable >the nullmove in your entire verification search. i don't understand why that >would be? can somebody explain? I don't know if this was from the posts I was making about problems I was having but that's not exactly the solution you want. The key point is that even when verifying a null move search you are still doing null moves lower down the tree and they could be causing problems too. However, you won't verify those becuase you are in verify mode. So now you are doing an R=3 null move and could miss some things. In my case I wasn't checking that Pieces != 0, thinking that the verify step would catch things. At the ply we're doing the verify on that would be correct but lower down the tree it could cause problems. I speculated on improvements that might change the null move conditions when doing the verification but I haven't yet had a chance to test these and see if they help. To be honest verified null move is off at the moment because it has not helped me. Andy.
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