Author: Robert Hyatt
Date: 13:53:14 05/15/98
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On May 15, 1998 at 10:40:52, Dave Gomboc wrote: >On May 14, 1998 at 08:57:46, Vincent Diepeveen wrote: > >>... could be true. This means [Fritz] simply has no knowledge about what >>to exchange. This is also the big weak point of Rebel. >> >>Ed schroeder states here that he is relying on leaf evaluation. >>In that case, rebel doesn't have code about what pieces to >>exchange. >> >>Main point is that you may not evaluate the exchanges. You should >>look to the material that you keep afterwards. So the resulting >>position. >> >>I dunno why Rebel+Fritz+genius and some others >>are so horrible in these exchanges, but my first guess was piece square >>tables. Now i say: perhaps mobility is a reason too. >>The common thing of all these programs compared to Crafty, Zarkov, Diep >>and some others is that they lack mobility terms. > >Crafty only has mobility for bishops at this point. I think Ferret is >not using a general mobility term either, if I recall correctly. The >trend has been to move away from measuring mobility (well or badly), not >toward it. > >Dave Gomboc Correct, but not for the reasons you'd suspect... IE it has nothing to do with performance, since mobility costs practically nothing in my code. But, in most cases, particularly for the queens and rooks, mobility is a "result of winning", not necessarily a "cause of winning." My very first eval in Crafty was 100% mobility. It didn't work well. Now, other terms replace mobility with more useful information, such as rooks on open/half- open files... this increases mobility, but is a measure of *useful* mobility rather than general mobility. The queen is a good example, that often if you move it to the square where it has the most mobility, that square is "gross"... from a strategic point... For bishops, I haven't done much yet, which is still on my todo list, so mobility is still used there. But for all the other pieces, I believe there are *better* positional terms than simple mobility...
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