Author: Robert Hyatt
Date: 13:30:18 09/20/99
Go up one level in this thread
On September 20, 1999 at 15:04:36, KarinsDad wrote: >On September 20, 1999 at 14:42:27, Robert Hyatt wrote: > >[snip] >> +---+---+---+---+---+---+---+---+ >> 8 | | | | | | | *K| | >> +---+---+---+---+---+---+---+---+ >> 7 | *P| *P| | | | *P| *P| *P| >> +---+---+---+---+---+---+---+---+ >> 6 | | | | | | | | | >> +---+---+---+---+---+---+---+---+ >> 5 | | | | | | | | | >> +---+---+---+---+---+---+---+---+ >> 4 | | | | | | *B| | | >> +---+---+---+---+---+---+---+---+ >> 3 | | | | | | | N | | >> +---+---+---+---+---+---+---+---+ >> 2 | P | P | P | | | P | P | K | >> +---+---+---+---+---+---+---+---+ >> 1 | | | | | | | | | >> +---+---+---+---+---+---+---+---+ >> a b c d e f g h >> >>This is the position prior to the last one. I (as black) played Bxg3. Old >>crafty promptly plays Kxg3 and now it has to watch out for the passed black >>pawn on the h file (eventually). new crafty plays fxg3 and black isn't going >>to make any passer. >> > >Looks impressive Robert. > >One question: How does this specific example work with rooks left on the board? >Having a position low in the graph of this example does not have a problem due >to the normal search preventing king threats and mate. However, if this pawn >evaluation is done 18 ply down, I could see a potential problem such as: > > +---+---+---+---+---+---+---+---+ > 8 | | | | | | | *K| | > +---+---+---+---+---+---+---+---+ > 7 | *P| *P| | | R | *P| *P| | > +---+---+---+---+---+---+---+---+ > 6 | | | | | | | | *P| > +---+---+---+---+---+---+---+---+ > 5 | | | | *R| | | | | > +---+---+---+---+---+---+---+---+ > 4 | | | | | | *B| | | > +---+---+---+---+---+---+---+---+ > 3 | | | | | | | N | | > +---+---+---+---+---+---+---+---+ > 2 | P | P | P | | R | P | P | K | > +---+---+---+---+---+---+---+---+ > 1 | | | | *R| | | | | > +---+---+---+---+---+---+---+---+ > a b c d e f g h > >Bxg3, fxg3 Rh5++ > >Do you have other code which forces you to check for king safety a few ply below >the pawn evalutation or do you just realize that event horizon is a problem >regardless and that if you are 18 ply down, there may be an alternative before >the actual position gets there anyway? > >KarinsDad :) King safety is a separate term... and don't forget, these scores are modified by the material remaining on the board. The less material, the more a outside passer or candidate outside passer is valued... And I only do the evaluation at the endpoints of the tree, using traditional alpha/beta, I _never_ use the eval to make forward pruning decisions or decisions that would say lets stop searching this branch here and go no further... This is an interesting piece of code, piece of knowledge. It will be interesting to see who doesn't have it now that I do, because it will become obvious. IE I can tell you who doesn't know about the bishop trap at a2/h2/etc, and who doesn't know much about outside/distant passers, because when I play them suddenly this term becomes important. This majority term will likely show up in similar ways for games that reach endgame status...
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