Author: Tony Werten
Date: 23:42:17 04/08/03
Go up one level in this thread
On April 08, 2003 at 18:15:33, Guido wrote: >On April 08, 2003 at 02:57:42, Tony Werten wrote: > >>On April 07, 2003 at 14:28:55, Dieter Buerssner wrote: >> >>>On April 06, 2003 at 16:09:02, Tony Werten wrote: >>> >>>>For simple EGTB: >>>> >>>>After placing the white king, there are only 63 squares left, after placing the >>>>white king there are only 62 squares left. So the index would be calculated >>>>((((SQWK*64)+SQBK)*63)+SQWR) >>>> >>>>SQBK (square black king ) would be adjusted as follows: if SQBK<SQWK then >>>>dec(SQBK) >>>>SQWR would be adjusted: if SQWR<SQWK then dec(SQWR); if SQWR<SQBK then dec(SQWR) >>>> >>>>That's the trick that saves space (well, to start with) Of course it has 1 nasty >>>>side effect: You can go from a position to an index, but it's quite impossible >>>>to get the position back from an index. >>> >>>I think it is easy. >> >>No it's not. The fact that it works in my simplified example doesn't mean >>anything, since nobody uses this. > >I use this in my EGTBs and it is OK also in a not simplified example. Do you include EP as well? That's where my "quite impossible" starts coming in. >I use tables for Kings and for 2 identical men; obviously I need of other tables >for each case if I want to go from a position to index and viceversa. >For 3 or more identical men I use mathematics for both the transformations. >In my opinion the difficulty of the inverse process in Nalimov EGTBs depends on >the fact that, in order to reduce the dimensions of the tablebases, positions >where there is a check, with the man close to the opponent king, are eliminated >from the file. You mean it becomes "quite impossible" in a real situation instead of a simplified example ? :) Mind you, I'm not sure it's impossible, it's at least very hard. Tony >Surely Bob or Eugene can say a final word on this problem. > >Ciao >Guido
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