Author: James Swafford
Date: 11:43:15 06/22/99
Go up one level in this thread
On June 22, 1999 at 09:50:26, Vincent Diepeveen wrote: [snip] > >> I have an idea; but I have not tried it as I am not a chess programmer. Extend >>on moves which drastically (this has to be defined) increase the mobility and/or >>decrease opponent's mobility. Moves which do the opposite can be forward-pruned, >>too. > >What is written above is crap. > I think that extending moves that increase mobility / decrease mobility is crapola, too, but the opposite (pruning moves which decrease comp's mobility / increase opponent's) would be an interesting experiment. I envision the first case by a bishop backing down to B1 to defend the A2 pawn. The mobility has been drastically decreased, but only to save a pawn. Should that move *really* be pruned? We probably shouldn't dismiss anything as crap without trying it, though. >To describe most common extensions; > > - check extension > always, or limit it. Why extend every check like e4,e5 Qh5,Nc6 Qxf7?? > - threat extension; if nullmove returns threat then extend. don't extend > all times nullmove returns threat. most common is to extend when > nullmove returns mate score. I call that mate threat extension. I limit > this a lot, yet this extension still works great. > >- recapture extensions; this never brought me anything, yet most programs > are doing it. i guess it's depending upon what you try in qsearch. the > more accurate your qsearch is the less you need of these is my thought. > i don't do them Doesn't do much for me, either, but it doesn't hurt so I leave it. > >- singular extensions; i've tried this thousands of times, but never found > them working. A singular extension is in fact a case of threat extension; > there is a threat that only allows a single move to prevent it by a > margin S. Threat extension doesn't have problems with S, and also extends > when more than 1 move prevents the threat. > >- passed pawn push extensions; i'm doing a few of those. can blow up your > search awful sometimes i limit it considerable. > >- one reply extension; when you only have 1 legal move, then extend it >independant from other extensions you already have in that pos (like check) > >- check evasion; after giving a lot of checks, it might be worth giving some > more checks (as a kind of selective search to find a checking sequence that > might mate). > >- high score extension. To prevent horizon effects to occur, one can > extend if a certain pattern is on the board which gives a high score > in evaluation. For example: if a queen is attacked, and you give a high > score for a queen being attacked, then you might want to extend it, > resulting in a better leaf score. Of course this extension needs to be > done near leafs and not in the middle of the search.
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