Author: David Franklin
Date: 14:54:16 08/21/99
Go up one level in this thread
>On August 19, 1999 at 18:12:35, Johannes Buchner wrote:
>
>>Hi there !
>>
>>I just wanted to know if anybody out there knows a different way how to do this
>>than using table-lookups like crafty. Is really no other mathematical
>>possibility ?
On August 19, 1999 at 20:59:28, Robert Hyatt replied:
>There's no mathematical method to compute this that anyone knows of, although
>that doesn't mean no such method exists.
I'm sure Bob already knows this one, but a 'mathematical' approach is to
note that 2 is a primitive root of F_67; In particular this means
2^N % 67 is unique for N = 0,...,63.
So something like:
which_bit = LUT[M % 67]; // M must have only one bit set
// of course can enforce this with
// M &= ~(M & (M-1)) or something similar
only requires a 67 entry lookup table. Unfortunately that % 67 evaluation
is going to be a lot slower than the standard approaches...
Dave
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.