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Subject: Re: Bean counters Part2

Author: Ernst A. Heinz

Date: 19:58:12 08/19/98

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On August 19, 1998 at 15:27:10, Peter Fendrich wrote:
>
>continuing from Part1...
>
>Method C (The Hacker trick without loops. Used by DarkThought)

Peter,

"DarkThought" is surely not the only one to use this famous HACKMEM trick.
But my article about "How DarkThought plays chess" explicitly mentions your
method A, too. The looping scheme is known to produce the best results
for sparsely populated bitboards. Therefore, we use normal and sparse
popcount functions/macros at different places in the code depending on the
expected population density of 1-bits. In the static evaluation function
the density is mostly low such that we use the sparse scheme there. During
move generation, however, you often encounter biboards that benefit a lot
from the HACKMEM scheme because they are heavily populated with 1-bits.

=Ernst=



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