Author: Robert Hyatt
Date: 10:38:38 10/11/98
Go up one level in this thread
On October 11, 1998 at 11:48:50, blass uri wrote: > >On October 11, 1998 at 10:47:07, Robert Hyatt wrote: > >>On October 11, 1998 at 03:07:04, blass uri wrote: >> >>> >>>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. >> >> >> >>but that's the problem and that's where this falls into oblivion. *if* I could >>do this, I would be doing forward pruning in the tree, because I would "know" >>that the first 32 moves contains the best move... But neither I nor anyone >>else knows how to do this. If I did, I would improve the algorithm to ensure >>that the best move is #1 in the list, and then I'd avoid searching anything. >> >> >>>> >>>> >>>> >>>> >>>>>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. >> >>I see lots of problems. Alpha/Beta needs a way to compare positions >>accurately. I want to know which position is best, not which group of >>positions are "equal"... > >If I have conversion in 97-100 plies my target is to force a conversion in 93-96 >plies if I cannot in 1 move against every reply of the opponent then I force it >by 2 moves >after 2 moves(4 plies) I did a progress of 4 plies in the distance to conversion >so there is no problem. >It is only important to get closer to conversion and I do it > >Uri except you aren't dealing with the reality of the current alpha/beta search, using transposition tables, which produces lots of search anomolies that are difficult to handle. At least "mate in N" works in every case I have found. "at least a mate, but I don't know how far away it is" is not so easy. Unless we toss the hash table out. And probably no one will do that... so yes, you can use DTC rather than DTM. Yes you can use "win lose or draw" flags rather than "mate in N". But do *I* want to deal with the complicated issues, when the current approach works perfectly? ..no..
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