Author: David Eppstein
Date: 18:02:38 07/20/99
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On July 20, 1999 at 16:43:47, Heiko Mikala wrote: >These sentences convinced me. Now, do you have any ideas, how such a "SCE" >could be implemented? Are there any existing papers about this, existing >algorithms? I know of no existing papers etc, maybe someone else does. But here are some half-baked ideas for categorizing checks: - Checks that set up an improved material balance. E.g. a fork, or a discovered check where the discovering piece can capture next turn. A move where the checking piece is on a safe square (i.e. attackers outweight defenders according to SEE-type examination) but which causes some opposing piece to become unsafe. If you can do a SEE quickly, it seems like you should be able to do this sort of check evaluation as quickly, and this is primarily what I was thinking about as the type of check you should look at in the qsearch. - Delaying tactics, checks that force a response but don't seem to make any progress in winning material. I'm not sure if you want to search these or not, probably not, but sometimes there might be a pot of gold (like checkmate) at the end of a long forced sequence of moves. Maybe you should depend on the regular search's check extensions to find these. - Stupid checks, that drop a piece (e.g. Bxf7+). Maybe they're not really stupid but you definitely don't want to spend a lot of time looking for them in the qsearch. Again, you should be able to figure out which ones these are using the SEE. So, if you can distinguish (roughly) between tactical checks, delaying checks, and sacrificial checks, it should be possible to do something useful with the knowledge. Include the tactical ones in the qsearch, maybe. Or use different amounts of check extension in the main search depending on what kind of check you think it is. Of course if you include checks in the qsearch, you also have to include moves that get out of check, so that the side making the check can have a chance to make the captures that the check was presumably setting up...so you definitely have to have some mechanism for avoiding searching a long time down perpetual check type lines. One quick and dirty way of doing this would be to not allow one side to make two non-capturing checks in a row...this might be a useful way to allow limited checks in the qsearch even without static check evaluation.
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