Author: Tony Werten
Date: 03:04:54 10/20/01
Go up one level in this thread
On October 19, 2001 at 18:41:10, Antonio Dieguez wrote: >On October 19, 2001 at 17:05:37, Tony Werten wrote: > >>On October 19, 2001 at 13:21:55, Christophe Theron wrote: >> >>>On October 19, 2001 at 03:02:28, José Carlos wrote: >>> >>>> Ok. It seems we agree in the background, but disagree in the surface. Software >>>>is much better now, true. Hardware has helped software developement, true. The >>>>point we disagree in can (I think) be said in a line: >>>> I believe that, if Frans would have back then the kind of hardware we have >>>>now, Fritz 3 would be much stronger, much closer to Fritz 7. And for the same >>>>reason, if we had now exactly the same machines as at that time, we couldn't >>>>have done many of the things we do now. That's all. >>> >>> >>> >>>Many improvements in software do not involve having a better hardware, they just >>>involve having time to work on the program, having ideas and having time to >>>implement them. >>> >>>It just takes time to imagine the new search algorithms and to work out all the >>>cases where your evaluation fails. For example it takes time to evaluate better >>>the passed pawns, and I can tell you it does not involve having a better >>>computer... >>> >>>Fritz3 is pretty poor at evaluating passed pawns. Frans did not need a better >>>computer to solve this, he just needed more time to work on the program, and >>>that's why Fritz4 was better in this regard, then Fritz5 was better and so on. >> >>I agree about needing time, but I don't think this is a good example. A couple >>of years ago, memory was quite limited, so no place for pawnhashtables. Without >>hashtables, evaluating pawnstructures is quite a hard job so it was kept simple. >> >>Passed pawns ( with other pawn stuff) is IMO an example of where hardware >>improvements improved the precision of the evaluation, more than just speed it >>up. > >Hi. > >How you do it? > >I don't have implemented yet pawn hashtables(in part because I don't believe >they would help me more than a bit, if), but how do you use it to handle passed >pawns? I suppose you store only the score? No, I just use it to identify some characteristics. >if so, how you do it to not calculate >passed pawns anyway in eval to see if it is obstructed or supported? You still have to do some work, but you can reduce it. My pawnhashtable consist of a lot of bytes where a bit is set if there is a passedpawn, doublepawn, backwardspawn or anypawn on that file. (so 4 bytes times 2 colors) This is quite expensive but on average I can take it out of the hashtable 99.9% of the time. So basicly I can do whatever I want in my pawnstructure code. Isolated pawns I dont store because they can be calculated by: onepawn[player] and not((onepawn[player] shl 1) or (onepawn[player] shr 1)) Further I hash the kingsafety left and rigth for both sides,( absence of pawns) and a score if the pawn is defended by other pawn etc. In my pawn evaluation I just and the line of the pawn with the byte to see what kind of pawn it is, then I look for the other stuff. So fe: if passedpawnbyte[color] and (1 shl (pawnfile))<>0 then //check if there is a piece in front of this pawn etc. If kingfile>E1 then safety[player]:=kingsafetyright[player]*weightedmateral if kingfile<D1 then .. else // king still in the middle if onepawn[player] and (1 shl kingfile)=0 then //your on a semiopen line if onepawn[oppo] and (1 shl kingfile)=0 then //even worse it's open etc >by the way >also the material on the board would be hashed?... No, only pawns. Your pawn hitrate would go down too much if you include it. Material is a different hashtable in my program(I have 5 in total) This has the funny sideeffect that my speed on ply 10 is about 5 times that of ply 2-3 ( still filling the tables) on testpositions. In game the difference is smaller but still noticable. Tony
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