Author: KarinsDad
Date: 07:09:24 01/07/99
Go up one level in this thread
On January 07, 1999 at 09:44:39, KarinsDad wrote:
>On January 07, 1999 at 02:30:08, James Robertson wrote:
>
>>On January 06, 1999 at 23:42:37, KarinsDad wrote:
>>
>>>I was reading all of the posts on the CountBits() function and couldn't for the
>>>life of me, figure out where I would need it.
>>>
>>>As I was working on my evaluator tonight, I suddenly realized, DUH.
>>>
>>>Thanks for all of the good information there guys!
>>>
>>>Is there anywhere else that it is used?
>>>
>>>Thanks again,
>>>
>>>KarinsDad :)
>>
>>I also use BitCount() in my check evasion function. It counts the number of
>>attackers attacking the king, which really helps decide my check evasion
>>options. :)
>>
>>James
James,
Sorry, I posted that other message by mistake. For check evaluation, I take it
you use this type of approach for BitCount() since only 2 bits can be set?
unsigned int BitCount(unsigned_64 b)
{
unsigned int n;
for (n = 0; b != 0; n++, b &= (b - 1));
return n;
Or is your datastructure set up to determine x-raying pieces where a knight
could move and then a queen puts the king in check and 2 rooks x-ray the queen
(for a true count of how many pieces are attacking that square). If so, wouldn't
the following code be faster?
unsigned int in_multiple_check(unsigned_64 b)
{
return ((b & (b - 1)) > 0);
Where you do not return the count, you merely return whether you are in multiple
checks. You could determine before you even called this routine whether you were
in check by seeing if b > 0.
KarinsDad
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