Author: Robert Hyatt
Date: 10:47:06 06/23/99
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On June 23, 1999 at 09:35:09, William Bryant wrote: >As I understand the use of Singular extensions, > when, after generating all the _legal_ moves, there is only one move to be > made by the side on move, extend 1 ply. > this isn't a singular extensions... this is a special case of singular extensions in general, and is most frequently called the "one reply to check extension." >Since you only extend a maximum of 1 ply at any node, if the King is in check, > or any other extensions are also triggered you would be extending anyway > and this only extends this branch of the tree when it is the only > condition extending the search. Depends. In Crafty, I extend 1 ply when I check the opponent. Then, if he has only one legal move, he extends 3/4 ply for that reason... still keeping the rule of "no more than one ply of extensions for every ply of search done." > >To generate legal moves, you must check each move to see if it places the King > in danger of being captured, a procedure that I do at present in my > MakeMove() function. The difference being, that it takes more time to > check for legality when generating the moves than it does in MakeMove() > because cutoffs keep you from making and unmaking all the moves. only check for legal moves if you start off in check. Because it is probably faster to weed illegals out if you start off in check, since most moves are illegal. But when not in check, I don't do this... rather I simply capture the king at the next ply to detect that the move at the previous ply was illegal. This also means that the one-reply extension _only_ works if you start off in check, which is perfectly reasonable... > >Now my question, is the extra time it takes to generate legal vs. pseudolegal > moves made up in the search by the singular extension during those > positions when nothing else would have triggered an extension in the > search anyway? > >Am I missing something? > >Thank you. > >William >wbryant@ix.netcom.com
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