Author: Peter Fendrich
Date: 02:03:30 09/28/04
Go up one level in this thread
On September 27, 2004 at 17:00:28, Robert Hyatt wrote: >On September 27, 2004 at 14:21:51, Stuart Cracraft wrote: > >>So when in PVS I've searched my first move, and it is a PV >>move as well, with search returning value then I do a depth-2 >>search on all other moves and if none -search(depth-2,-beta-MARGIN,- >>alpha-MARGIN) <= -beta-MARGIN, where MARGIN is set to 3/4 of a pawn, >>then the PV move is singular and I re-search it with depth instead of depth-1 >>and use the returned value as my score against which to >>measure all other non-PV moves against in the normal part >>of the search, searching them to depth-1. >> >>Is the above wrong? >> >>Stuart > > >It is wrong. > >Search the first move with the normal window. Search the _remaining_ moves with >an offset window alpha-w, beta-w. If all still fail low (which they should do >if the first move is best) then the first move is singular. re-search it again >with a deeper search. If one of the remaining moves fails high on the offset >window search, now you have a problem. Is this move better than the best move? >If not the best move is not singular. But, this move could itself be singular >so you have to test that hypothesis by re-searching the first move with a window >lowered by the usual offset from the score returned by the second move that >failed high. Repeat until sick or finished. > >You are describing what is done for determining singularity at fail-high nodes >where only one move is normally searched before returning, but you do the >"cheaper" searches to try to prove singilarity anyway and extend even a >fail-high move one ply... Both alpha-w and beta-w. Wouldn't that make the hash table even more unstable than it is already? I mean "put entry" with one window in the first search and "get entry" with another window in the next re-search? /Peter
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