Author: Stuart Cracraft
Date: 21:33:32 01/29/98
Sorry about the absurd subject, but I had to get your attention somehow. :-) Here it is... When I sort moves, most of the moves don't fall into a standard category that gets assigned a non-zero score (killers, captures, hash moves, history heuristic valued, etc.) Instead, most moves end up in the "other" category. This category ends up giving the move a zero score. Most scores therefore were in the bottom of the heap and chosen randomly, actually in the order that the move generator generates them (knights first, then kings, then bishop, rook, queen, pawns last), since my sort doesn't change locations of moves or pointers to them and leaves the zero-scored ones in the same order as the move generator generated them. So recently, I added a centrality perturbation that added 15 minus the taxicab distance from the move's destination square to the center of the board (chosen as E4 since I wanted to avoid real arithmetic to 4.5.) Anyway, the result was a major drop in search speed on certain searches and a drop in results in Win-at-Chess from 204 to 199 positions solved out of 300, just for the lousy centrality perturbation of the move sort order. Anyone else seen this kind of thing? I didn't even change the static evaluation. Nothing else was changed. --Stuart
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