Author: Gerd Isenberg
Date: 11:12:16 12/27/02
Go up one level in this thread
<snip> >>>>Hi Vincent, >>>> >>>>That's interesting. >>>>I thought backwardness is independent of pieces (per definition) and could >>>>therefore been calculated without considering pieces and stored in the >>>>PawnHash-Table?! >>> >>>This is the major problem of most scientist in computerchess. They >>>see one time in their life a definition of something and then use >>>that till they are old and grey. >> >>Or until you elucidates them. > >regrettably the english-dutch dictionary >is downstairs because we have australian guests, >but i guess i understand the meaning :) enlighten, clarify, clear up... > >>One amazing thing with backward pawns is, that everybody comes up with sample >>positions, but Bas initial questions still remains open, geay area. > >I must have missed the postings from Bas but i am not sure i would have >answerred it anyway (nothing personal Bas!) :) > Hmm... makes me thought-provoking. Must be your bitboard competence ;-) >>My current approach don't considers b7 as backward, because of duo, but as a >>target for a rook on a halfopen file. > >>Anyway, the approach Bas mentioned works even well with your definition, if one >>considers piece attacks in the domination bitboards. > >that will be pretty fast with bitboards. Adding up how many attackers and >defenders you have whereas i just do a single AND from my attacktable >in order to find out how many attackers there are and what kind of >attackers ;) > Ok, for one square. I guess your attacktable generation is as negligible as my attack-getters. Rather than looping over all pawns, looking for some properties, the bitboard approach gets appropriate pattern for all pawns of one side. But of course, if the cardinality of the sets becomes one, the relative performance decreases. Maybe that's your point. Pattern shrinking may occur conditionally, eg. if i have no open pawns with no counter pawns on stop or advanced stop squares, there is no need to look for passers. openPawns[WHITE] = pawnBB[WHITE] & ~filldown(allPawns >> 8); if ( openPawns[WHITE] ) passedPawns[WHITE] = openPawns[WHITE] & ~filldown(pawnAttacks[BLACK]); >>> >>>However evaluation is a big grey area. >> >>Yes for sure. >> >>> >>>For a human b7 in the example is backward. Of course a major problem >>>from chess literature versus evaluation in a chessprogram is the classical >>>case where in human chess there are only 2 types of bishops. A good one and >>>a bad one. >>> >>>In my chessprogram there are dozens of bishops though so i ran out very >>>quickly out of names and invented new ones. >>> >>>However bishop evaluation is a peanut compared to pawn structure code. >>>This is a clear example of that. >>> >>>Bruce sees it as the result of tactical pressure that b7 is backwards. >>> >>>That is of course true, but it is a backward pawn from a pawnduo. >>> >>>Whether you advance c7 to c6 or not. b7 keeps backward. When i play away >>>the rook, then b7 is not backwards in DIEP's evaluation but still a little. >>> >> >>OK, but with pawn on c6, b7 is really or better statically backward. > >It depends upon the position simply. > >>>>What is the exact reason whether c5 is not backward. >>> >>>as i said: c5 is isolated pawn. Not a backward pawn. >>>c5 is a very strong pawn here. >> >> >>But also isolated pawns may be backward. Isn't it necessary to distinguish >>between isolated that may push forward or not? > >>- - - - - - - - >>- - - - - - - - >>- - - - - - - - >>- - - - B - - - >>B - - - - - - B >>W - - W - - B - >>- W - - - - W - >>- - - - - - - - >> >>Here b2, d3 and h4 are backward, but not e5 because it's more advanced than it's >>counterpart d3. > >b2 is backwards. h4 is backwards. d3 is isolated. e5 is isolated. > >I do not see d3 in diep as backwards here. I do not see it myself as >backwards either. If there would be a pawn on e3 or e4 it sure would be >yes. So with your definition isolated and backward contradict? > >of course there is too many pawns exchanged here to look the pawn >structure like a middlegame. > >However i hope you realize that the further an isolated pawn like e5 goes >the easier i could win it for white. getting d3 is very hard though. Aha i see, interesting aspect. > >So i do not understand your definition that d3 is weaker than e5 from >that viewpoint. It's the backward-pawn definition by Kmoch, the sample is directly fom his book "Die Kunst der Bauernführung" (Page 233): "Was die Bauern d3 und e5 im selben Diagramm anbelangt, läßt sich folgender Satz aufstellen: Stehen sich zwei Einzelbauern im Hinkerabstand gegenüber, so fällt die Rückständigkeit auf den mit der längeren Frontspanne." Wrong definition, or simply outdated? > >On the other hand if you do not have very good mobility in your program, >this is a way to say kind of: "because the pawns of black are further >than from white, black has more mobility so let's give the penalty for >the pawn structure instead of black bonus for mobility; the netto >result is the same evaluation". > >Bit primitif said but i hope you can understand what i mean. > Yes, i have it. These interferences make the eval even more a gray area. >>>Again something to go wrong easily. I can remember so many games of >>>DIEP at the auto232 players of Jan in the past where a strong pawn >>>was by means of tactics very quickly a weak pawn and then the pawn >>>was lost and the game some moves later too. >>> >>>So c5 is a very strong isolated pawn here. >> >>But i guess it's so strong because of the interaction with b7 and c7/c6. And it >>crossed already the boarder, a fact where backwardness may become an advantage, >>specially if there is only one (dynamic) backward guard. >>The black pawn on c7 disguises the "backwardness" of c5. The weak or dynamic >>backward pawn on b7 makes c5 not backward. >> >>Isn't that the fundamental idea behind minority attacks? Even if the stop square > >minority attacks is something completely different. Aha, sorry for my lack of chess knowledge. I know that an isolani against a duo is not a minory attack per se. But is this kind of forcing backwardness or other pawn-weaknesses not a matter of minory attacks? Regards, Gerd
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