Author: Uri Blass
Date: 17:26:04 10/08/03
Go up one level in this thread
On October 08, 2003 at 19:29:05, Omid David Tabibi wrote:
>On October 08, 2003 at 09:51:01, Robert Hyatt wrote:
>
>>On October 08, 2003 at 06:33:00, Sune Fischer wrote:
>>
>>>On October 07, 2003 at 20:19:00, Russell Reagan wrote:
>>>
>>>>>I'm sure you could make use of that 8x8 array to implement non-bitboard
>>>>>functions where appropriate and use the bitboard ones where they're more
>>>>>convenient, taking advantage of both approaches; I don't know why this has to be
>>>>>regarded as a dichotomy!
>>>>
>>>>Unfortunately many of the advantages of 0x88-like systems cannot be taken
>>>>advantage of using a 64-element array.
>>>
>>>What are the many advantages of 0x88-like systems?
>>
>>The most important are "is square xxx on the same diagonal as square yyy"
>>along with "is square xxx off the edge of the real board?"
>>
>>There are similar questions easier to answer with bitboards.
>
>I use a simple board[64] representation. No bitboard, no 0x88...
same for me.
If you have a
>handy attack table, the board representation is insignificant. When using
>bitboard, you get the attack table built-in, using other methods you have to
>write your own attack table (I use 32 bit per square).
>
>In a simple board[64], you can check a square's diagonal by:
>
>#define DIAG1(x) (((x) >> 3) + ((x) & 7)) // y = x diag
>#define DIAG2(x) (((x) >> 3) + (((x) & 7) ^ 7)) // y = -x diag
I have it only for rank and files.
The question is when this information about diagnols can help me.
Maybe it already can help me in things that I do but I do not think about them
in this moment.
I use in some cases the array direction[64][64] that gives different number for
different directions(include queen and knight directions).
>
>But I don't use the above anymore. Attack tables give the needed data.
>
>And checking whether a square is off the edge of the board can be very easy
>using a "mailbox":
>
>const int mailbox[] = {
> -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
> -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
> -1, 0, 1, 2, 3, 4, 5, 6, 7, -1,
> -1, 8, 9, 10, 11, 12, 13, 14, 15, -1,
> -1, 16, 17, 18, 19, 20, 21, 22, 23, -1,
> -1, 24, 25, 26, 27, 28, 29, 30, 31, -1,
> -1, 32, 33, 34, 35, 36, 37, 38, 39, -1,
> -1, 40, 41, 42, 43, 44, 45, 46, 47, -1,
> -1, 48, 49, 50, 51, 52, 53, 54, 55, -1,
> -1, 56, 57, 58, 59, 60, 61, 62, 63, -1,
> -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
> -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
>};
>
>And address the above table using:
>
>const int mailbox64[64] = {
> 21, 22, 23, 24, 25, 26, 27, 28,
> 31, 32, 33, 34, 35, 36, 37, 38,
> 41, 42, 43, 44, 45, 46, 47, 48,
> 51, 52, 53, 54, 55, 56, 57, 58,
> 61, 62, 63, 64, 65, 66, 67, 68,
> 71, 72, 73, 74, 75, 76, 77, 78,
> 81, 82, 83, 84, 85, 86, 87, 88,
> 91, 92, 93, 94, 95, 96, 97, 98,
>};
I do not have these arrays and I have some arrays like leftdown[sq](usually sq-9
but can be -1 in case that sq-9 is not in the same diagnol).
I do not understand why mailbox and mailbox64 are better than arrays like
leftdown[64].
>
>Using bitboards is a matter of taste. I personally don't like bitboards because
>it is not easy to extract the data you need for the evaluation function. Of
>course people like you and Gerd who "think bitboard" can find nice tricks to
>handle those issues, but still extracting data out of board[64], color[64] is
>easier :)
I have info[64] that include both color and piece and I get the color or the
piece by defines.
Uri
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