Author: Vincent Diepeveen
Date: 14:19:13 04/09/03
Go up one level in this thread
On April 09, 2003 at 02:42:17, Tony Werten wrote: >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. it isn't even that difficult, but the question is whether you want to do it. Because how are you going to generate the 6 men with such slow indexing schemes? i use very simple index scheme in diep. means you can generate the stuff. nalimov needs major supercomputer for that (he has it though). >Tony > >>Surely Bob or Eugene can say a final word on this problem. >> >>Ciao >>Guido
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