Author: David Dahlem
Date: 16:02:54 12/28/05
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On December 28, 2005 at 18:39:28, Dann Corbit wrote: >On December 28, 2005 at 17:11:30, David Dahlem wrote: > >>On December 28, 2005 at 16:24:53, Dann Corbit wrote: >> >>>On December 28, 2005 at 16:03:47, David Dahlem wrote: >>> >>>><snip> >>>> >>>>>If you have a bitboard program, there is a way to get really cheap mobility >>>>>scores. >>>> >>>>Could you elaborate on this method? >>> >>>Precalculate for every ray, based on the bit pattern on that ray. >>> >>>Move generation is also helped by this idea (both for capture/promotion and >>>non-capture). >>> >>>consider this epd string: >>>[D]4k3/1n6/8/pR5b/1P6/1n6/1N6/4K3 w - - >>>For the rook's row, we have 1x000001 ( the x is because we ignore the square he >>>sits on, he can never attack or defend that.) >>>For this simple case, the non-captures are the zero squares and the captures are >>>the non-zero squares anded with the opponent chessmen mask. >>>Regardless of what the chessmen are, there are 5 non-captures and 0,1,or 2 >>>captures depending on whether the 1 bits are friend or foe. >>> >>>For the column we have 010x1110. >>>There is one non-capture and 0,1, or 2 captures depending on whether the nearest >>>one bits are friend or foe. >>> >>>You get the idea. >> >>Thanks Dann. Mobility should only be considered for bishops, knights, rooks, and >>queens, is this correct? > >I would test it in your eval for benefit. Tord does not calculate queen >mobility, for instance. > >If you use bitboards, you can calculate the total pawn mobility in a couple >operations. I think it is a lot more important in the endgame (e.g. down a >piece with +3 pawns and your pawns are rammed sounds like trouble). > I'm currently only using bitboards to calculate mobility for bishops and rooks. I haven't even considered doing mobility for pawns. >>And I'm thinking the bonus should be scaled according >>to piece values? > >I do a fitted curve using parabolic least squares fit from actual data. At >least it gives you a good starting point. >YMMV. I'm not a math expert, so "fitted curve using parabolic least squares" leaves me mystified. :-) Regards Dave
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