Author: James Robertson
Date: 12:22:34 11/19/99
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On November 19, 1999 at 14:33:26, Alexander Kure wrote: >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. This still is slower than the one line I posted earlier. That line does not have to be in the evaluation function, so it should always be faster than computing an index and looking up a tb value, even if the tb is in memory. I still think these special tablebases loaded into RAM are a waste of space. James >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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