Author: Dieter Buerssner
Date: 15:38:52 05/30/02
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On May 30, 2002 at 08:43:06, Guido wrote: >It is exactly my computation. I said that if 8 bits are not sufficient, it is >not necessary to use 16 bits, but 9, 10 or more, depending on the longest >sequence of that particular ending, so the problem is how to manage a carry >different from 8 bits. I implemented an algorithm to realize this idea and write >the correspondent code, but at present I have no possibilities to check the >correctness of this part of the program. I think, I understand, at least partitially. I wonder however, how one could know the number of bits needed in advance. To give a simple example. KRK is at most a mate in 16 and obviously never lost. So we need (ingoring illegal positions, which we could code as draw) a bit more than 4 bits :-). Without going through the complications of coding (say) 15 values in 8 bytes, 5 bit would be a good start. But when you start generating the TB, how can you know this (without doing the work twice)? >The problem you spoke about is different and is related to the fact that endings >with pawn occupy a lot of space and spend a lot of time, so it could be useful >to subdivide the single tablebases, keeping into account the irreversibility of >the movement of the pawn. But IMHO in this case, at first sight, it is not >possible to work in parallel, and even more the same is true for pawnless >endings. Hmmm. As an example the perhaps most useful of all TBs - KRPKR (at least for programs, that do not have sophisticated knowledge of this ending). When KQRKR, KRRKR, KRBKR and KRNKR are available, one could start to calculate KR(Pa7)KR, KR(Pb7)KR, etc. in parallel. Why not? When the "rank 7" TBs are available, one could calculate the rank 6 TBs in parallel, and so on. After all, there can only be a conversion to the higher rank TBs. >I put this program in exe code on my site, but before informing CCC, I asked to >g_6 group members (a group of italian programmers) to check the results and the >use of my TBs in their programs using a very simple object library present on >the same site. I have to revise the explanation in english and to update the >program getting it faster, but if you are interested now, I'll send you >privately the site address. Thanks for your offer. I am a patient man, and can wait (and experiment myself). Ciao, Dieter
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