Author: leonid
Date: 12:19:22 12/31/01
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On December 31, 2001 at 10:58:46, Heiner Marxen wrote: >On December 31, 2001 at 07:44:24, leonid wrote: > >>Hi, Heiner! >> >> >>>>What is "immediate mate move"? >>> >>>If the defender is to move, and the current depth is at least 3 (mate-in-2 >>>or more left after defender move), and the defender has more than just his bare >>>king, then, before even generating the legal defender moves, Chest calls >>>the special mate-move-generator, trying to find a "mate the attacker in 1". >>>The moves found by that move generator are just candidates, and must be >>>executed to verify them, but there are not many false candidates. >> >>This is probably what I expected to write but never come to my code. Recently I >>put all kind of counters in plys three. What is interesting to see there is that >>biggest part of all positions for this ply have checking moves. So, if this side >>use its checking move and have certain number of legal moves for his king, it >>have good chances to escape mate after response. All work should be in finding >>how many initially legal king's moves are needed. Also it is important to see if >>each if its moves do not diminish number of already existing king's escape >>moves. > >With "ply three", do you mean the defender is to move as part of the mate-in-2, >with the attacker asked to solve a mate-in-1 after this move? Yes! >If so, then yes: most of these moves are checking moves, and almost all of >them are quite successful. In Chest I have a special handling for this. >The main thought (from the perspective of the defender) is: >- After the move I will select now, he (the attacker) is trying to mate me. > I will keep him busy by checking him, so he has to defend to the check, > instead of checking me. Exact! And since in my program all checking moves are already at the head of the chain, I should use some data that it already there. >- Ok, I could check him with this piece from there. Now, could he defend > against that check and at the same time check me? > Well... if his king moves out of check... could be a discovered check > to me, at most... but from there, where his king is leaving to there, > where my king still is, there is no geometric connection... no discovered > check. This is very close to what I expect to see but, like in the past, I will do it in parts. First I will see how many times king can escape the mate when its side (I speak about 3 ply) give check to whites. Only after this I will look into second part, when on ply 3 blacks have no moves to check but black king have around 5 moves or more. This possibility is very much present in position that you brought today. >More cases and details are tested, until one finds, that the defender by >checking the attacker in a certain way, already avoids any mate in the next >move. In Chest I estimate that by verifying that the attacker cannot even >follow up with a checking move. I call that "fatal anti check", FAC. >This is a very successful heuristic. >Well, I learned "heuristic" as a technical term in computer science. Before I read a lot about programming but it was only Assembler related books. Nothing about chess. I don't remember "heuristic" word on all my reading. After your previous message I went to search in "Oxford American Dictionary" for 1979 "heuristic". Wanted to "refresh my mind". Dictionary is around 50000 words but this word is missing. >>>Holger was interested to do research and experiments on this, and tried >>>to work on the tree size estimation idea. He spent 2 weeks of his vacations >>>on this, and came back with an extended version of Chest, which now solved >>>that mate-in-9 much, much faster. Actually, it was the first time that >>>we did solve that position (took 32.5 hours on a HP9000-835 in 1991). At the time when my first mate solver version was done, in around 1995, this position could easily take months to solve. >>If this man was able to do everything in two weeks, he was stronger that me. > >Not "everything", just the extension :-) >Also, trying out ideas is _much_ faster in C than in assembler. >That is the main reason for me to not use assembler, any more. When you write only for fun, Assembler could be the most amusing thing to use. I like its freedom. >>I was coming all two weeks with some kind of new ideas and biggest part of them >>never worked. > >I forgot to mention: we also introduced options for all three authors, >so that every author can trigger his own extensions without disturbing the >research of the others. Anyway, it is a good idea to make extensions >conditional, so one can play with and without them, until the case is settled, >at which time a default is chosen. > >>>So I took his code, cleaned it up somewhat, added some comments, and >>>asked him about all those peculiar details in there, which I did not >>>understand. Most often he could not explain much more than "I tried >>>several things, and this worked best... don't know why". >> >>So, he, probably, did like me after statistics. Cheers, Leonid.
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