Author: Stuart Cracraft
Date: 22:01:04 09/27/04
Go up one level in this thread
On September 27, 2004 at 23:56:17, Robert Hyatt wrote: >On September 27, 2004 at 23:48:56, Stuart Cracraft wrote: > >>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... >> >>Ugh -- sounds like a coding mess. I've saved your comments in a futurefile >>but probably won't do much on SE until my computing resources are faster. >>Giving up a ply for long-shots against humans is enticing of course as long >>as the ply loss won't kill me due to very deep searching anyway -- that >>won't happen until my box is 5x faster and that won't happen for awhile. >> >>So at this point not sick but "pending". >> >>Stuart > > >It _is_ a mess. By the time you do both PV and FH singular tests, add in the >sticky transposition table stuff, you see why I occasionally question a "certain >poster" that claims (depending on the day of the week) that (a) SE is no good or >(b) he has implemented SE and uses it. It is non-trivial to do if you do _real_ >SE. I don't know about a poster but it certainly looks complex enough to make me only want to implement the "cheapo" version that I heard Chess Genius uses which I assume is some variant on the PV-only singular extension piece and not for at least a year or few.
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