Author: Daniel Shawul
Date: 01:48:18 04/10/04
Go up one level in this thread
On April 09, 2004 at 02:30:36, rasjid chan wrote:
Hi
The AllPieces bitboard was what is left when i flipped from bitboards
to 0x88. I thought it would help me in checking if a piece can slide between
two squares. But it didn't. Doing while loops is as fast as the bitboard
method on my pc. What i am saying is it may be good for a full Bitboard
programme, but i am not sure if it helps for others. Another suggested place is
to use them for pawn evaluation. This one i didn't try but i don't think it
would do me anything good.what i am doing now is just loop through the pawns
before i started eval of pawns [like tscp does] and fill my data. Since i use
pawn hashes this is done rarely.
best
daniel
>
>
>I have a set of simple macros for bitboard operations and they are meant for
>those with a new chess program and like to implement fast complete
>attacks by bishops and rooks. It is basically just three #define and all sliding
>attacks would then be available for use in evaluations and move ordering. Of
>course it is only when we don't yet count instruction cycles,
>but then after things are moving we could EASILY upgrade to
>rotated bitboards.
>
>The only requirement is that the "all" bits must be available. Most chess
>programmers sooner or later will have to use some bitboard operations as
>there seem no escape for the sliding pieces and it is usually necessary to
>incrementally update the "all" bits after makemove()and unmake().
>
>These bitboard operations just make use of simple direct intuitive
>operations.If we have a single bit x, then x - 1 divides the board into
>upper half and lower half and add to it some bitwise operations which
>everyone say is fast. The only memory access is U64 diagonal[2][15]
>and it is much better than U64 attack[64][64].
>For those not using 0x88, they just need some simple editing.
>
>If anyone has something faster or can make them faster, please post.
>
>Best Regards
>Rasjid
>
>
>typedef unsigned _int64 U64
>
>#define GetFile64(sq) ((sq) & 7)
>#define GetRank64(sq) ((sq) >> 3)
>#define iGetFile(sq88) ((sq88) & 7)
>#define iGetRank(sq88) ((sq88) >> 4)
>#define sq88Bit(sq88) ((U64)1 << (((sq88) + ((sq88) & 7)) >> 1))
>#define sq64Bit(sq64) (((U64)1) << (sq64))
>#define sq88RankBits(sq88) ((U64)0xff << ((sq88) >> 1 & 0370))
>#define sq88FileBits(sq88) ((U64) 0x0101010101010101 << ((sq88) & 7))
>
>//*** global variables
>U64 all, diagonal[2][15];
>
>
>//*** Start - bitboard attack operations for sliding pieces
>
>/*
> This test that the in-between arc (x, y) is clear of any bits.
> path is the complete bit path along x, y across the board
> */
>
>#define brq_path_clear(x, y, path)
> ((x) <= (y)
> ? ((x) == (y) || isqBit(y) - 1 & ~(isqBit(x) - 1 | isqBit(x))
> & (path) & all ? 0 : 1)
> : (isqBit(x) - 1 & ~(isqBit(y) - 1 | isqBit(y))
> & (path) & all ? 0 : 1))
>
>/*
> given any two sq88 x, y , this test if they attack along
> diagonals.
> */
>
>#define bstyle_attack(x, y)
> (iGetRank(x) + iGetFile(x) == iGetRank(y) + iGetFile(y)
> ? (brq_path_clear(x, y, diagonal[1][iGetRank(x)
> + iGetFile(x)]) ? 1 : 0)
> : (iGetRank(x) - iGetFile(x) == iGetRank(y) - iGetFile(y)
> ? (brq_path_clear(x, y, diagonal[0][7 + iGetRank(x) - iGetFile(x)])
> ? 1 : 0) : 0))
>
>/*
> given any two sq88 x, y , this test if they attack along
> rank or file.
> */
>
>#define rstyle_attack(x, y)
> (iGetRank(x) == iGetRank(y)
> ? (brq_path_clear(x, y, isqRankBits(x)) ? 1 : 0)
> : (iGetFile(x) == iGetFile(y)
> ? (brq_path_clear(x, y, isqFileBits(x)) ? 1 : 0) : 0))
>
>
>//*** End - bitboard attack operations for sliding pieces
>
>
> void pre_calculate_diagonal(){
> int i, j, l;
> //get diagonal[2][15]
>
>
> memset(diagonal, 0, sizeof(diagonal));
> //LR down == [0][7 + r - f]
> //RL down == [1][r + f]
>
> i = 0;
> while(!(i & 0x88)){
> l = iGetRank(i) - iGetFile(i);
> assert(7 + l >= 0 && 7 + l < 15);
> for (j = i; !(j & 0x88); j += 17){
> diagonal[0][7 + iGetRank(j) - iGetFile(j)] |= isqBit(j);
> assert(l == iGetRank(j) - iGetFile(j));
> }
>
> l = iGetRank(i) + iGetFile(i);
> assert(l >= 0 && l < 15);
> for (j = i; !(j & 0x88); j += 15){
> diagonal[1][iGetRank(j) + iGetFile(j)] |= isqBit(j);
> assert(l == iGetRank(j) + iGetFile(j));
> }
> ++i;
> }
>
> i = 16;
> while(!(i & 0x88)){
> l = iGetRank(i) - iGetFile(i);
> assert(7 + l >= 0 && 7 + l < 15);
> for (j = i; !(j & 0x88); j += 17){
> diagonal[0][7 + iGetRank(j) - iGetFile(j)] |= isqBit(j);
> assert(l == iGetRank(j) - iGetFile(j));
> }
> i += 16;
> }
>
> i = 23;
> while(!(i & 0x88)){
> l = iGetRank(i) + iGetFile(i);
> assert(l >= 0 && l < 15);
> for (j = i; !(j & 0x88); j += 15){
> diagonal[1][iGetRank(j) + iGetFile(j)] |= isqBit(j);
> assert(l == iGetRank(j) + iGetFile(j));
> }
> i += 16;
> }
> }
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