Author: Ernst A. Heinz
Date: 08:02:52 04/19/00
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Hi Flemming, >I am trying to implement a bitboard based chess program on a Pentium or AMD >computer. I need to be able to find the following information fast: > >1) The position of the first and/or last bit in a sequence of 64 bits. >2) Count the number of bits that are 1 in a sequence of 64 bits. > >I know there is a method that works linear in the number of on-bits for >problem 2: > > for(count = 0; bitboard; count++, bitboard &= (bitboard -1)); > > >Is there anything faster, ie. such lookuptables or machine code intrutions? > >What about problem 1? > >Thanks in advance for any reply My article about "How DarkThought Plays Chess" in the ICCA Journal 20(3), pp. 166-176, Sept. 1997 contains some valuable information about your subject of interest. Please have a look at the WWW pages of "DarkThought" at URL http://supertech.lcs.mit.edu/~heinz/dt/ in order to find an electronic preprint of this article among others. =Ernst=
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