Author: Alexander Kure
Date: 11:33:26 11/19/99
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On November 19, 1999 at 13:57:01, James Robertson wrote: >On November 19, 1999 at 06:29:39, Alexander Kure wrote: > >>Hi, >> >>There were some postings recently about Nimzo 7.32's handling of simple standard >>engames like KR-K, KBB-K, KBN-K where Nimzo 7.32 was not able to deliver mate. >>Well, the reason is quite simple: As long as the 3 and 4 piece endgame >>tablebases are installed and properly loaded when starting Nimzo 7.32, he will >>have no problem to mate. Now the question is what happens to Nimzo when >>confronted with these kind of endings where he has no access to endgame >>tablebases at all? The answer is quite simple: *All* endgame code regarding >>these endgames was removed from Nimzo 7.32. So when deprived of access to 3 and >>4 endgame tablebases he has *absolutely* no idea what to do as there is no code >>in the evaluation to tell him what to do! >>Of course one can argue that this is nonsense and Nimzo 7.32 were to keep his >>endgame knowledge no matter if he uses endgame tablebases or not, but in the age >>of tablebases it seems not necessary anymore. >>You can test this with Nimzo'99, who still has this code and who has no problem >>to mate KR-K, KBB-K and KBN-K. >>So instead of using Hiarcs 7.32 as your alternative endgame engine maybe you >>could give Nimzo'99 a try ;-) >> >>Greetings >>Alex > >To be quite honest, I think this is either false or a dumb idea. It has already >been posted that Nimzo's tablebases don't give the distance to mate; therefore, >they are useless for mating. For instance, almost every KRK position will say >"mate!". That is wonderful, but if the winning side decides to move his king to >a1 and his rook to h8, he still has "mate!" in the tablebase scores. And if King >on a1 and rook on h8 is just as good as any other KRK position, Nimzo will never >make progress. Therefore, Nimzo _must_ have some other mating scheme. > >Also, you can replace Nimzo's entire KRK tablebases with one line: >if (losing_side_pieces==KING && winning_side_pieces==KING+ROOK) return MATE; > >And save a TON of space. That is why I think that the tablebases for some >positions (KQK, KRK, KBK, KNK, KBBK, etc.) are not such a good idea. > >James Hi James, Maybe there is some misunderstanding, so i will try to clarify: Nimzo is accessing the Ncd-Endings in the quiescence search. As this is a memory (not a file) access it should be faster than even calling the eval function. So when detecting a won ending, like e.g KR-K the search stops there knowing it is won. Back again at the root (i.e. ply 1 -n where n is a set by the user) when it really comes to the position Nimzo 7.32 uses Nalimov in order to determine the fastest winning move. Maybe you were confused by assuming that Nimzo 7.32 uses *only* his endgame tablebases, but of course this is not the case, as you already suspected. Greetings Alex
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