Author: Robert Hyatt
Date: 07:40:19 03/07/02
Go up one level in this thread
On March 07, 2002 at 08:30:02, Slater Wold wrote: >On March 07, 2002 at 03:43:00, Uri Blass wrote: > >>On March 07, 2002 at 00:42:56, Slater Wold wrote: >> >>>On March 06, 2002 at 23:40:28, Robert Hyatt wrote: >>> >>>>On March 06, 2002 at 22:49:38, Slater Wold wrote: >>>> >>>>>On March 06, 2002 at 22:27:17, Uri Blass wrote: >>>>> >>>>>>On March 06, 2002 at 19:18:16, Slater Wold wrote: >>>>>> >>>>>>>Hyatt said in an earlier post that TB's don't take into account the ability to >>>>>>>castle because it would be a waste. >>>>>>> >>>>>>>However, when I feed this position into any engine, it solves it in 0.00 as a TB >>>>>>>win. >>>>>>> >>>>>>>[D]5Q1Q/5Q1Q/5Q1Q/5Q1Q/8/6P1/6k1/4KR1R w K - >>>>>> >>>>>>Your FEN is wrong and we need to imagine that all the white queens that you >>>>>>copied from dann corbit's post are missing. >>>>> >>>>> >>>>>You're right. But obviously this is not the position I am talking about, >>>>>because I don't have the 13 man TB's. :) >>>>> >>>>> >>>>>>>It shows 20 possible moves, all from TB's I am guessing. >>>>>>> >>>>>>>I cannot cut and paste the eval, because there isn't one, but I have: >>>>>><snipped> >>>>>>>1.+ - (#4) Rf4 >>>>>> >>>>>>This is not correct and the program that you use has bugs. >>>>>>It should not call tablebases in a position that is not in the >>>>>>tablebases(castling is legal) >>>>>> >>>>>> >_Several_ of these moves take castling into accout. >>>>>>> >>>>>>>After Rf4 Kxg3 my TB's show 28 moves. The first move is 1. + - (#2) O-O, the >>>>>>>last is 28. + - (#15) Rh8. >>>>>>> >>>>>>>I am 100% sure TB's do indeed take castling into consideration. >>>>>> >>>>>> >>>>>>No >>>>>>You do not understand how tablebases work. >>>>>>There are no moves in tablebases. >>>>>> >>>>>>The engine generates all the legal moves and looks in the tablebases after these >>>>>>moves to see distance to mate. >>>>> >>>>> >>>>>Um, well, according to Hyatt, it would tell the TB "o-o" and it wouldn't return >>>>>anything. I am very well aware how TB's work. >>>> >>>>Not quite. First I _never_ said anything like that. With EGTB's you don't >>>>give them a move, and get back a score, you give them a _position_ and you get >>>>back a score. And the score says "mate in N from the given position, >>>>assuming castling is impossible." >>>> >>>> >>>> >>>>> >>>>> >>>>>>If castling is legal then the engine looks at the tablebases to see the distance >>>>>>to mate after castling in order to see the mate in 2 score. >>>>> >>>>> >>>>>According to Hyatt, no it doesn't. >>>> >>>> >>>>You are greatly twisting things around. Re-read what Uri wrote... >>>> >>>>"if castling is legal then the engine only checks the TB _after_ castling >>>>has been done." Because after castling has been done, it can't be done again >>>>and the resulting EGTB score will be correct. Prior to castling, the score >>>>will be wrong because castling is possible but the EGTB scores don't include >>>>castling. >>>> >>>> >>>> >>>> >>>>> >>>>> >>>>>>Uri >>>>> >>>>>The correct position is: >>>>> >>>>>[D]8/8/8/8/8/6P1/6k1/4KR1R w K - >>>>> >>>>>Sorry. >>> >>>I am not trying to "twist" anything around. You said TB's don't take into >>>account castling. Ok, fine. I believe you. I open a chess engine, and it's >>>returning o-o as a TB move. NO EVAL NEEDED. I am asking a simple question. >>>Why?! How is an engine returning a mate, without TB's, without an eval? >>> >>>If it's a stupid question, I apologize. I just don't understand, obviously. >> >>Very simple answer >> >>0-0 is not a tablebase move because the tablebases have no moves but >>only positions and evaluations. >> >>The position after 0-0 is a tablebase position. >>The engine tries every legal move and look at the tablebases >>to get a score for the position after the move. >> >>I can add that the way the engine is using tablebases is wrong >>and it can cause mistakes >>on positions when the only win is based on the idea to castle in the second move >>and not in the first move. >> >>In this case the engine may return draw score for every move because it is going >>to look at the tablebases that are based on the assumption that >>castling is illegal in the future. >> >>It is of course not important for practical games because castling is not >>allowed in practical games so I understand programmers who choose not to fix the >>problem. >> >>Uri > >Thanks Uri. But I am still not convinced. > >When I put this position into a CB engine, I can monitor CPU usage, and I know, >it _never_ uses the CPU. o-o doesn't not have an eval. > >Last time I checked, when an engine "evaluates" a problem, it gives an eval. It >also usually uses some CPU time. Evaluating a single position takes what? a millisecond? You think you could see that on the CPU meter? If the position at the root of the tree (the position after o-o) is a tb position, the computer makes every possible move, one at a time, and then probes the TB. It chooses the move that has the best possible TB score. It is _definitely_ doing some work. But the work is a few milliseconds at most, a few microseconds at best. You can't see that on a "cpu meter"... > >Not so in either case here. I am not sure what's going on. But thanks for >trying to explain. :)
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