Joost Buijs wrote:
Every good chess player sees immediately that Black is dead lost,
That rules me out then !!
Well, I don't imply that I'm a good player either, but after some consideration I saw that it is won easily mainly because the black bishop is out of play.
This is typically a position that is very well suited to test your engine with.
Joost Buijs wrote:
Every good chess player sees immediately that Black is dead lost,
That rules me out then !!
Well, I don't imply that I'm a good player either, but after some consideration I saw that it is won easily mainly because the black bishop is out of play.
This is typically a position that is very well suited to test your engine with.
Well, the awkward Black Bishop is only one (the smaller) reason. The main reason
is that the Black King cannot leave a certain area because of the immediate
breakthrough g6 which creates an unstoppable passer.
This means Black has to play w/o King here, which is of course immediately lost.
Joost Buijs wrote:
Every good chess player sees immediately that Black is dead lost,
That rules me out then !!
Well, I don't imply that I'm a good player either, but after some consideration I saw that it is won easily mainly because the black bishop is out of play.
This is typically a position that is very well suited to test your engine with.
Well, the awkward Black Bishop is only one (the smaller) reason. The main reason
is that the Black King cannot leave a certain area because of the immediate
breakthrough g6 which creates an unstoppable passer.
This means Black has to play w/o King here, which is of course immediately lost.
Yes, that is why I talked about zugzwang.
The white king can eliminate the black pawn on the a file and after that walk to the other side of the board, game over.
Most engines have difficulties finding this in a short time, probably due to null-move.
Henk wrote:Still don't understand why Embla played 57. Qd2 giving away a queen.
Most likely because it's buggy, but more popular is to come up with a better excuse, such as a hash collision
The Embla version that can be downloaded for Windows (I tried the 64 bit version) does not consider Qd2?? as best move during the first 20 iterations (which is more than one minute). So it is either due to a new bug in the version that played the tourney, or some mysterious condition during the game ... I would expect the former, based on the overall result of Embla.
Joost Buijs wrote:Every good chess player sees immediately that Black is dead lost, many engines just don't find it because there is zugzwang (null-move).
If null move search is turned off, my program finds the win in a depth of 25.
There have been previous comments about identifying more zugzwang positions for null move search, especially for minor piece endgames. Currently, null move search is typically rejected for pawn endgames only. Rejecting a null move search for minor piece endgames can add other problems related to lack of depth. Is there any research going on in the area of formulating further null move search zugzwang conditions?
One idea I have experimented with is examining the absence of free pawns in a position. (A free pawn is a pawn that can advance safely). However, the positions are still too complex to combine with minor piece endgames.
Joost Buijs wrote:my guess is that it has something to do with null-move.
Exactly! I'm running a patch now that doesn't do nullmove if stm has no more than bishop in non-pawn material.
Too early but seems to be even after 1400 games so I'm willing to accept it if it holds (of course I need more games
I also have a NullMove option in my engine so I can turn it off completely.
It's tempting to get rid of nullmove completely, but that would cost a lot of elo...
EDIT: I wonder if it would be viable to scale the aggressiveness of the nullmove based on stm's non-pawn material
