Author: Christopher Conkie
Date: 02:07:19 02/24/06
Go up one level in this thread
On February 24, 2006 at 04:13:34, Gerd Isenberg wrote:
>On February 23, 2006 at 18:45:34, Dann Corbit wrote:
>
>>On February 23, 2006 at 17:37:21, Gerd Isenberg wrote:
>>[snip]
>>>>a1b2 is a 64 bit unsigned integer with bits a1 and b2 set.
>>>
>>>Huch! That is possible!?
>>>Hopefully no indirect jump table with 2**64 entries ;-)
>>>Is that inside the generator or inside the chess programs.
>>
>>For a given square, I need at most 128 constants per row or diagonal.
>>
>>They are precomputed.
>>
>>Obviously, you must have the 64 unique bitboards A1-H8 defined.
>>
>>Then, your generator program writes (above the functions themselves):
>>
>>printf("static const Bitboard a1b2 = %ui64;\n", A1|B2);
>>
>>Any given file will need 128 for each column and 128 for each row and between 0
>>and 128 for each diagonal for both diagonals.
>
>Thanks, i have it now. Was too dazed by the switch(BitBoard). Hmm, yes as far i
>can see the switch with up to 128 cases translates chain of 32-bit
>compares/jumps.
>
>Intuitively without having a closer look to some generated assembly i tend to
>favour the De Bruijn folding with distinct directions, even if less flexible in
>terms of xrays and other data-structures used for see. Otoh a quadbitboard
>filler also provides xray informations as well - at least for usual and well
>predictable cases with not more than two rooks, one queen and one bishop per
>square color and side.
Hello Gerd,
I'm sorry I just got it in my brain about Dann's method and then you said
"quadbitboard filler". Could you explain this in a little bit more detail for my
creaking brain please? Do you have some pseudo code to illustrate this? I have
to admit that these methods hover around what I was originally thinking.
I noticed your thread with De Bruijn which was also eye opening. In these days
of 64 Bit OS's all of the above seems to be essential knowledge.
Christopher
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