Author: JW de Kort
Date: 03:28:31 12/17/02
Go up one level in this thread
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
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