Author: JW de Kort
Date: 03:46:33 12/17/02
Go up one level in this thread
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. > >If it is often losing against tscp after playing gambit lines then it means that >something is wrong with it's search. > >I also believe that the way to work on evaluation is not to implement a lot of >things in the evaluation but to add one thing and to test if there is an >improvement or if you do not expect a big improvement to test to verify that >there is not a big regression. > >I test my program often against gerbil in 1 second/game,...10 seconds/game when >my program use no book and always change the first move. > >The last result that was the best so far is 275-125 for movei. >at 5 minutes per game I got with an older version 32-5 and 3 draws >so I believe that the gap between movei and gerbil is bigger at longer time >control. > >Note that Movei may play stupid gambits like 1.e4 f5 in the conditions that I >test but it simply has better search and evaluation than gerbil and these >factors dominate. > >Uri
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