Author: Uri Blass
Date: 04:28:54 12/17/02
Go up one level in this thread
On December 17, 2002 at 06:52:43, JW de Kort wrote: >On December 17, 2002 at 06:44:52, Uri Blass wrote: > >>On December 17, 2002 at 06:28:31, JW de Kort wrote: >> >>>On December 17, 2002 at 05:57:55, Uri Blass wrote: >>> >>>>On December 17, 2002 at 05:46:29, JW de Kort wrote: >>>> >>>>>On December 17, 2002 at 04:46:16, Uri Blass wrote: >>>>> >>>>>>On December 17, 2002 at 04:27:48, JW de Kort wrote: >>>>>> >>>>>>>On December 17, 2002 at 03:40:11, Uri Blass wrote: >>>>>>> >>>>>>>>I think to add to my program bitboard that will be used only for pawn structure. >>>>>>>> >>>>>>>>2 numbers of 64 bits that are used for white pawns and for black pawns. >>>>>>>> >>>>>>>>I want to detect based on these bitboards a lot of information about every pawn >>>>>>>>and I may want to use the information together with attack tables for >>>>>>>>evaluation. >>>>>>>> >>>>>>>>My question is if using bitboard is a good idea to get the information and >>>>>>>>if the answer is positive how can I detect the information by bitboards >>>>>>>> >>>>>>>>For every pawn I want to detect the following: >>>>>>>> >>>>>>>>1)Is it a weak pawn(a pawn that can never be defended by a pawn and cannot go >>>>>>>>forward to promote without captures and without the risk of being captured by a >>>>>>>>pawn) >>>>>>>>2)Is it probably weak pawn(it means that the only way to defend it by a pawn is >>>>>>>>by capturing the opponent pawn or by letting the opponent to capture the >>>>>>>>potential defender by a pawn). >>>>>>>> >>>>>>>>3)Is it a pawn that is defended by a pawn and if not how many normal pawn moves >>>>>>>>that are not captures and do not let the opponent to capture by a pawn are >>>>>>>>needed to defend it by a pawn. >>>>>>>> >>>>>>>>4)Is it a passed pawn and if it is a passed pawn how many normal pawn moves are >>>>>>>>needed to defend it by a pawn. >>>>>>>> >>>>>>>>5)Is it a potential passed pawn(is the only way of the opponent to stop it is by >>>>>>>>letting the player to have another passed pawn) >>>>>>>>In case that it is a potential passed pawn the question is if it can be done by >>>>>>>>normal means or the only way to make it a passed pawn is by sacrifices >>>>>>>> >>>>>>>>Uri >>>>>>> >>>>>>>Dear Uri, >>>>>>> >>>>>>>I do this in my 0x88 based program: i use bitboards to do the pawn evaluation. >>>>>>>This evaluation is only on a very basic level but the topics you mention is >>>>>>>covered. I found out that by bitboard it is far easier and quicker to check >>>>>>>whether a pawn is passed or not but i think this is commom knowledge. I found >>>>>>>the source of Crafty very informative. >>>>>>> >>>>>>>regards >>>>>>> >>>>>>>Jan Willem >>>>>> >>>>>>1)This seems to be not very basic level. >>>>>> >>>>>>In the match steve ham against computers Nimzo7.32 could not evaluate correctly >>>>>>a black passed pawn at c3 that could not be protected by a pawn and gave it a >>>>>>big bonus. >>>>>> >>>>>>If even Nimzo7.32(that is at the level of the top amateurs) could not evaluate >>>>>>it then it means that it is not a basic evaluation because I expect nimzo7.32 to >>>>>>know at least everything that is very basic level. >>>>>> >>>>>>I guess that big majority of the chess programs do not have this information >>>>>>because most amateurs have less knowledge than nimzo7.32(movei of today even >>>>>>does not evaluate passed pawns). >>>>>> >>>>> >>>>> >>>>> >>>>>I'am afraid my response was not completely clea at this point or maybe i got >>>>>your question not right. M<y progrma can tell if a pawn if passed atc. by using >>>>>bitboards but iám not to say that it is evaluated correctly. My engine is very >>>>>weak at the moment and one of the problems is the wrong evaluation of these >>>>>features. I understood your question as; how to detect these things. Iám sorry >>>>>if i under estimated you. (I wonderde why you asked this question to be honest). >>>>>By 'basic' i mean that an evaluationfunction coveres all the aspectes that are >>>>>already in the function of CHESS 4.5. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>>2)Where did you look at crafty source code to find the relevant information that >>>>>>helped you? >>>>> >>>>>I took a close look in the evaluationfunction where the pawns are evalutaed. But >>>>>i think it is not to hard to understand this. e.g if you want to know if a pawn >>>>>is passed you can do a logical AND with the bitboard of all opposite pawns and >>>>>an bitboard giving all the squares that must be empty for the pawn to be passed. >>>>>(Again i appologize if this information is not what you are looking for). >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>> >>>>>>Note that I plan to use the information for the evaluation but it does not mean >>>>>>that this information will give me the evaluation because I want to evaluate >>>>>>weak pawn that is attacked by the opponent as less than weak pawn that is not >>>>>>attacked by the opponent so I may use my attack tables. >>>>>> >>>>>>3)What is the level of your program? >>>>>> >>>>> >>>>> >>>>> >>>>>Not very good i'am afraid. The evaluationfunction does know almost all the >>>>>features of CHESS 4.5 like passed pawns, backwardspawns, very backwardspawns, >>>>>doubled rooks, rooks and quens on seventh rank, kin safety, caslte bonus for >>>>>being casteld and a malus for not being so, king tropism, center tropism, >>>>>placement of pieces like near the centre and on safe squares etc. but these >>>>>features are at the moment so badly tuned that my program is willing to open up >>>>>his king defence to advance his pawns. But again this is only for starters, >>>>>since it can play under winboard iám planning to make it stronger. My main >>>>>concern however is the speed, or better the lack of it. I saw it beat BEOWULF >>>>>once but i saw it beaten by BEOWULF about twenty times. It largely depends on >>>>>the opening my progrma plays if it can give some resistance. >>>> >>>>My programs knows almost nothing about it but it is clearly better than programs >>>>like Gerbil. >>>> >>>>My question is what is the level of your program relative to other chess >>>>programs. >>>> >>>>Uri >>> >>>Dear Uri, >>> >>> >>>I have never let it play agains Gerbil, but i will do that soon. I had it play >>>against Fritz 6 with the obvious result. It plays about 50-50 agains TCSP (or is >>>it TSCP i'am not sure) but i do not like this program to test is againt (but is >>>very usefull to get information from) because it always plays the same moves. My >>>progrma uses a large openingbook wich contains gambits and if my program plays a >>>gambit it is a sure loss because the lost pawn will never be retrieved and my >>>progrma does not know how to exploid the possitional advantages. Agains BEOWULF >>>it plays better then i expected but it also most of the time loses but i have >>>seen it a few times. The problem with my progrma is that the evalutaion function >>>is not tuned and i hope to find time to work on it. >>> >>>So i would say my engine is relatively weak but i think -or hope- it has >>>potential to grow. >>> >>>Greetings JWK >> >>I think that the problem with your program is that you worked on the wrong >>direction. >> >>search is clearly more important than evaluation. > >That might by true but i have implemented already some search things like >iteratieve deepening, captures first, killer moves, hash table, hisotry >heuristic and i am planning for null move and extansions but after that i found >out that my progrma lacked knowledge. > > > > > > > > > > > >> >>If it is often losing against tscp after playing gambit lines then it means that >>something is wrong with it's search. > >I don't think i agree. If i see it correctly the purpose of a gambit is to give >up material to gain positional advantage. THis is ok if you kno how to use this >positional advantage and this involves knowledge. If you don't know how to >exploit the advantage you just give away material like my program does. I believe that if you let it search deeper at the same opening it is going to beat tscp. I suggest that you try the same openings that your program lost but only let it to search 2 plies deeper than it searched in the games. I expect it to win most of the games that it lost. Uri
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