Author: Tord Romstad
Date: 08:34:14 01/08/04
Go up one level in this thread
On January 08, 2004 at 10:02:39, Anthony Cozzie wrote: >I've been trying to get some good test positions to rewrite my kingsafety with, >and playing Gothmog will give you those :) Cool. That better and more experienced programmers than myself start using Gothmog to test their king safety against is an indication that I achieved some of my goals with this engine. :-) >Usually Zappa is slightly better than >Gothmog. It is stronger tactically (gets more nps and does not do all dubious >forward pruning) I'd attribute this to your higher nps than to my forward pruning, I think. Gothmog is much stronger tactically with forward pruning than without. >and its mobility is good enough that it plays reasonable moves >most of the time. Usually Zappa will get its wins in the endgame, Just wait. I'm working on the endgame right now, and hope that my engine will be much stronger in that phase of the game in time for the CCT. :-) >but Gothmog will get in enough king attacks that the score is close. Really? This is good news to me. I thought Gothmog was not even in the same league as Zappa, and that it would have no chance whatsoever in a match. >During one of the test games, this position came up (Zappa-white, >Gothmog-black): > >[D]r2qk2r/pb4pp/3bn3/1P1ppp2/8/BQP5/P2NBPPP/R4RK1 b kq - 4 17 > >Where Gothmog evaluated itself as +1, and Zappa thought it was about equal - >which is of course ludicrous since black has a big advantage. I was less than >happy with Zappa being blown off the board in 20 moves and not even realizing >it, so I wrote some code to evaluate control of the board. But I made a mistake >and tuned it way too high. Too high? Does this mean that it gave bad results against other engines than Gothmog? >What was amazing was the result. Every game went like this: > >Zappa pushes pawns >Gothmog sacrifices a piece for the pawns >Gothmog thinks its down .5 >Zappa thinks its up 2 >Zappa wins back pawns and the game with its extra piece/exchange > >Result: Zappa scores 86% - +18-0=7. > >Moral of the story: If you want to beat Gothmog, triple your space evaluation. Very interesting -- thanks for sharing the results and observations. I don't really have any good ideas about what causes this amazing result, but here is my first wild shot in the dark: I've noticed that Gothmog's own space evaluation seems to be a bit too high. It is possible that it panics when Zappa builds up a space advantage, and sacrifices a piece in an attempt to neutralize the advantage. At any rate, I now have something to work on. Once again, thank you very much. It's very brave of you to share your observations *before* the CCT, rather than after. :-) >anthony > >caveat: This was done under Arena, with the arena books, which need a bit of >work. I am not very familiar with Arena or the Arena books (I don't use Windows), but I don't think these playing conditions should hurt Gothmog. Gothmog's own book is not particulary good anyway. Tord
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