Author: Uri Blass
Date: 14:46:40 03/31/03
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On March 31, 2003 at 15:20:35, Martin Giepmans wrote: >On March 31, 2003 at 14:35:48, Uri Blass wrote: > >>Today latest movei evaluates passed pawns and protected passed pawns based on >>the ranks of the pawn(I will later change it to evaluate them >>based on other factors like square of the kings). >> >>The problem is that the order of evaluation is not correct. >> >>If I have a pawn at b5 and another passed pawn at c5 then >>I want to evaluate them as better than pawn at b4 and >>protected passed pawn at c5. >> >>I thought to give a bonus for passed pawn that has pawn in the left side of it >>but the problem is that in that case the evaluation is not >>symmetric and in the folowing diagram if the black pawn is in c6 and not f6 >>I get different result. > >I think giving bonus/2 if there is a pawn on the right OR on the left side >would do the trick. It's symmetrical. > >> >> >>[D]8/7k/5p2/8/3PP3/8/8/K7 w - - 0 1 >> >> >>Another problem is what to do when there are 3 passed pawns. >> >>[D]8/7k/8/8/3PPP2/8/8/K7 w - - 0 1 >> >>In that case even if I decide to give only one bonus for pair >>I may get here 2 bonuses and after the central pawn progress >>one square forward I will have only one bonus. >> >>I wonder how other programs solve that problem. >> >>protected passed pawns are good but other things are also good and the problem >>is how to order the things in the right order. >> >>Uri > >In my engine I give a bonus for a passed pawn that is >(a) protected by a pawn (left or right) >or >(b) has a pawn on the left or on the right > >If both are not true (pawn is not protected and has no neighbor) I give a >small penalty. The penalty is so small that it will not hinder the advance >of the passed pawns. But it helps the engine to keep it's pawns "together". > >Cheers, >Martin Today I have a small bonus for passed pawns in all cases based on the rank of the pawn. I do not think that it is a good idea to have a panelty for passed pawns even if they have no neighbour becuase there are cases when they are dangerous. 2 passed pawns at a and h file may be very dangerous and beat easily 3 connected pawns c,d,e in a pawn endgame. I know that there are cases when they are weak so I decided to have no bonus and no panelty for them in my previous version but I found based on games that a small bonus with no panelty seems to be slightly better than nothing I may continue later by adding a panelty to cancel the bonus in part of the cases. I do not do big changes but one change and after it testing and the question is how to evaluate passed pawns in a way that better will evaluated as bigger. giving 1/2 bonus for every pawn that is in a pair is not a good idea because 3 connected pawns on the same rank may get 4.5 bonuses (1 for every one of them for the fact that it is a passed pawn and 3/2 bonuses for the fact that they are in pair). The problem is that if the central pawn advance you have only 4 bonuses(1 for everyone and 1 for protected passed pawn). You can claim that 3 connected passed pawns are not very common but I still do not like the evaluation. Uri
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