Author: Adrien Regimbald
Date: 22:59:15 08/12/00
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Hello, >I can detect that there is no mate in 1 for white without searching because one >piece cannot cover all the 9 squares. > >I do not need to search all possible moves of white to know it. >Chest use these kind of ideas and this is the reason that it is the best mate >solver. Of course I know there are techniques like this to cut down on things for a mate solver. I was not speaking of whether it was POSSIBLE or not, I was working under the assumption that we were talking of a normal search. This is sort of like me saying you can't juggle 10 balls at once under the assumption that you're on the back of a 747 aircraft, and you replying with "But a certain juggler can juggle 10 balls!". I _know_ you could find jugglers which can juggle 10 balls, but it's completely irrelevant to the issue at hand. There are two problems here: - If you do tricks like with chest to eliminate lines, you might miss good lines to play for material/positional reasons. - If you only look for good lines to play (a la alpha-beta or MTDF or whatever your favourite method is) you will miss lines that are possibly mating. The claim was that he was doing a depth <x> search and guaranteeing he saw all mates with only a 1% penalty. The problem is that most typical searching methods leave out huge portions of the tree. I will agree that you can quickly check for short mates along the branches which you actually search, but I must disagree on the issue of being able to see ALL possible mates up to depth <x> with only a 1% penalty. This would mean that if you had a tree like this: o /|\ o o o / < x > o /| o o / \ \ a b c A normal search would typically see a, b, c, and skip almost all of x (well, of course this is a gross over simplification, but you know what I mean). Call this search a 4 ply search (no q-nodes). In order to determine all mates possible up to 4 ply for this position, you'd have to be exploring a great portion of x, which sort of ruins the whole approach to computer chess search, don't you think? (well, I know it would be possible to write an algorithm to determine that some of the moves in the later 2 branches made it impossible to mate within 4 ply, but I'm thinking that this would come at a LOT more cost than 1%) I have yet to see a program which will do it's normal search to depth <x> and be able to tell you with absolute certainty whether there is a mate within that depth available. You could easily write one which performs such a task, but once again, that is not the issue, the issue is doing that same task while also calculating high calibre chess moves. Regards, Adrien.
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