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Subject: Re: Differences between 0x88 ,10x12 and Bitboards!?

Author: Russell Reagan

Date: 12:12:15 11/19/02

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On November 19, 2002 at 13:57:02, Vincent Diepeveen wrote:

>Yet a crucial aspect of evaluating is scanning and that's something
>where bitboards are handicapped with 1 or 2 exceptions (you can
>quickly scan a rank or file for presence of a piece X).

In an 0x88 engine, you have to do potentially 8 tests to scan for the presence
of a piece on a rank or file. Even if you are lucky enough to have zero branch
mispredictions (doubtful), you still do 4 increments, and 4 tests on average. In
bitboards it's one AND (or two on 32-bit machine) with 1 test, or at most two
AND's, an OR, and 1 test. How is 4 inc's + 4 tests better than 3 bitwise
operations and 1 test?



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