Author: blass uri
Date: 00:07:04 10/11/98
Go up one level in this thread
On October 11, 1998 at 00:42:55, Robert Hyatt wrote: >On October 10, 1998 at 00:56:05, blass uri wrote: > >> >>On October 09, 1998 at 22:54:49, Roberto Waldteufel wrote: >> >>> >>>On October 09, 1998 at 18:46:36, David Eppstein wrote: >>> >>>>On October 09, 1998 at 15:24:26, Robert Hyatt wrote: >>>>>This doesn't matter however, because *every* possible position must be accounted >>>>>for, with an exact distance to mate for the side on move with that specific >>>>>piece configuration. So they *all* have to be computed to build the next one >>>>>after them... >>>> >>>>You don't need distance to mate if you are searching from a non-tablebase >>>>position trying to reach a tablebase position (and aren't worried about the 50 >>>>move rule, but you must not be since you're using distance to mate). >>>> >>>>If the actual game reaches a won tablebase position, you need some way to force >>>>progress, but it doesn't have to be distance to mate. If you can always search >>>>deeply enough to find a conversion (capture or pawn move), you can use distance >>>>to conversion, and only store win/loss/draw in the tablebase. In any KXP-KP or >>>>KX-KPP endgame, searching deeply enough to find a conversion should be easy >>>>(there are fewer than a million distinct positions in which at most one pawn has >>>>moved, so you can load just that part of the tablebase into memory and use the >>>>hashtable to do the search quickly no matter how deep it is). >>>> >>>>But I agree with your main point, that the heuristics suggested by the poster >>>>you were responding to aren't good enough -- the information needs to be exact, >>>>and you need to compute lots of other tablebases before you can think about >>>>KPP-KP. >>> >>>Even if the search were too deep to be feasible, eg an ending like KBBKN, it is >>>still possible to reduce memory access requirements during the search by storing >>>only win/loss/draw information, if we maintain a separate tablebase (not used in >>>the search) which simply contains the best move >> >>You need memory to store the best move for example in KBBKN for the stronger >>side the maximal number of legal moves is 8+13+13=34 legal moves >>and you need 6 bits for a move so I think you do not save memory by this. >>If you have a good order of moves and always 1 of the first 32 moves is best you >>can need only 5 bits >> > > >I don't want to sound "harsh" but let's not get rediculous. Exactly *how* >can we generate moves and *guarantee* that the best move is in the first >32? That is completely *impossible* to do, and discussing it makes no sense >at all. > >Also, in databases, we *do* *not* store "moves". That is a misconception of >some sort. Moves are not stored, only the status of each possible position. I know that we store a number for every position and the numbers represent moves but I understand that the idea of roberto is to to store numbers that represent moves and to store the result(only in win,draw,loss) instead of storing numbers that represent exact results In KBBvs KN we can do for every position a list of legal moves such that the moves that lose a bishop without giving the oppoent to mate in 1 or causing the distance of the kings to be longer are in the end of the list. If in all the positions there is a best move from the 32 first moves in the list we can store the right move by 5 bits. > > > > >>If you store distance to conversion with my idea you need only 5 bits >>for 1-2,3-4,...49-50,draw,loss >>You need to do a search but I do not think there is a problem with small search. >> >>Uri > > >this kind of statement isn't helping, either. "I do not think..." is not >a convincing argument. you need to search only to improve the score. and if 2 plies are not enough you search for 4 plies "I implemented this and can prove that it will work" is >going to convince me a lot quicker. I did not try to implement it but I see no problems with the idea. "thinking" doesn't cut it here. It *has* >to be right or it will certainly be wrong... And wrong we can't stand, because >we trust these results *perfectly*... I agree it has to be right but I do not see a reason why it is wrong The algoritam is simple and the only problem I can see is a problem of time but I understand that 1000 hits on the tablebases per position is not a problem and you do not need more to search 4 plies(for most of the lines you need only 2 plies and 4 plies are only for best defences of the loser). Uri
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