Author: Larry Griffiths
Date: 08:08:21 01/14/01
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On January 14, 2001 at 00:36:52, Uri Blass wrote: >I am interested to know what is the fastest way that is known to evaluate >mobility in bitboard when the definition of mobility is the weight of the number >of squares that the pieces control. > >For example if a bishop at c1 controls the squares d2,e3,f4,b2,a3 then the >mobility of it is >weightbis[d2]+weightbis[e3]+weightbis[f4]+weightbis[b2]+weightbis[a3] when >weightbis is an array(I can call it a mobility square table). > >I am interested to know if bitboard is faster or slower than other ways to >calculate this evaluation. > >Uri Im glad you posted this Uri. My previous program generated all the captures and moves and used the total count as a mobility value. This worked pretty well but it wanted to move the queen out early in the opening because it can move to so many squares. I had to penalize the queen for moving in the opening to stop this. I am missing this function with my current bitboard version as I do not extract all the moves from the bitboards. I extract the captures, then extract the moves if a cutoff does not occur. I do generated both a capture bitboard and a move bitboard during move generation, so I am thinking of maybe or'ing all the capture and move bitboards for each piece together and then counting the bits in the result bitboard, using it as an indicator of mobility. I would have to use QSearch to determine if pieces are on proper squares so that tactical battles are not lost. I have a MinMax function that can produce over 2 million move generate/make/unmakes per second, but that number falls down to about 200,000 a second when I add cuttoff's, hashing, evaluation etc. I am convinced that a good evaluation function is important, and mobility is certainly a factor to be considered. Keep posting and let me know if you find and goodies :) Larry.
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