Author: Gerd Isenberg
Date: 03:08:16 02/24/06
Go up one level in this thread
On February 24, 2006 at 05:07:19, Christopher Conkie wrote:
>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
Hi Christopher,
actually a bit short in time - thanks for your interest and also thanks for
starting this thread. I will post some explanation later.
Gerd
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