Author: Willie Wood
Date: 12:11:05 11/25/97
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On November 24, 1997 at 19:44:44, Robert Hyatt wrote: > >I'm not sure what Bruce does. I do mobility for bishops, as there is >not a lot of other things that can tell whether the bishop is a good one >or a bad one... But it doesn't have to be an expensive calculation, if >you use the right data structures. IE mobility is "free" for bitmap >programs... > Right. I don't use bitmaps, so it's an issue. I'm pretty sure Bruce mentioned that he doesn't use mobility, so I thought he might pipe up. I'll send him a note. > >I have used fractional ply extensions for about 15 years. The idea is >that >a normal check can extend 1 ply, but if there is only one legal way out, >I >let this extend by 3/4 of a ply. The 3/4 is critical, because a single >such extension does nothing (3/4 < 1). but the second such extension >will >trigger an extra ply, as will the third and fourth, then the fifth won't >extend, but the next 3 will. This provides a throttling effect to >prevent >a non-terminating search. Just be aware that following too many checks >is >just as bad as following too few. You want to find the obvious mates so >you >don't get killed, but there is no real need to find a mate in 30. I've >played >in computer vs computer and computer vs human games for almost 30 years >now >and have *never* seen a program of mine announce a mate in 30, nor have >I >ever found a position where such was important. If you go too far, you >waste >time that could be used in other ways... Ok, think I've got it now. I was using a material difference window, plus a restriction on the number of files/ranks the king could travel, plus a repetition test. But it still explodes occasionally. I'll try the fractional extension. Thanks. WW
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