Author: Oliver Roese
Date: 21:58:14 07/01/00
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On July 01, 2000 at 19:28:19, Dan Homan wrote: >I keep meaning to retire EXchess and write an engine with some >more advanced techniques like bitboards or 0x88, but I always >end up coming back to EXchess to try "one more thing". > >The "one more thing" that I have been meaning to try for a while >is Temporal Difference evaluation learning (e.g. knightcap) because >it seemed simple to implement and I hate to manually tune my evaluation >... so much so that I haven't spent more than a few hours on tuning >the parameters. > >Now I can report my first impressions with TD learning. I sat down >this week and spent a few hours on a couple of different nights putting >it into my program and debugging (which took most of the time). I can say >that the TD learning code (at least what I've done so far) is not much more >difficult to implement than tablebase probing. The knightcap guys really >lay it all out very well in their published papers. > >My code is still messy and there are some issues I still need to work >on. With that said, I did try it out on the piece values in my program. >I started the values at > >PAWN = 100 (fixed) >KING = 10000 (meaningless, so learning should not affect it) >KNIGHT = 0 >BISHOP = 0 >ROOK = 0 >QUEEN = 0 > >and played a 100 game, 1 0 lightning match against GNU-chess. After the >match, the parameters were at > >PAWN = 100 >KING = 10000 >KNIGHT = 296 >BISHOP = 327 >ROOK = 508 >QUEEN = 997 > >Which are pretty close to my "hand-tuned" values. I did interfere with >the match after game 25 to reduce the learning rate from a mean of 100 >points per update to a mean of 10 points per update. (The actual update >to the piece scores depends on the details of the given game and could >be a few times the mean or a modest fraction of the mean). My decision >of when to reduce the learning rate probably influenced the final values, >but I am not certain by how much... after 25 games the values were within >a 100 points of the ones above but with lots of noise from game to game. > >This has been a fun little project and I have lots of issues to examine >and improve in my particular implementation, but it seems to work and >rather well at that. Eventually this stuff will end up in a future >release of EXchess, but probably not for several months at least. > >If any programmers are interested, I can discuss rather generally the >types of changes I needed to make to my program to get this to work. > > - Dan I am interested. What type of changes do you mean? Oliver Roese
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