Author: Sander de Zoete
Date: 14:38:47 01/13/03
Go up one level in this thread
On January 13, 2003 at 16:50:57, Bas Hamstra wrote:
>On January 13, 2003 at 16:43:01, Sander de Zoete wrote:
>
>>Heb je geen suggesties?
>
>Well in fact it is interesting. But I have no experience with it. From what I
>understand the X & (X-2) does a sort of floodfill left-up so you keep a reversed
>bitboard to get a floodfill right-down. I have to experiment with it to be sure
>what it does... Back in 2 minutes, after which I will give you advice for the
>next 2 years...
>
>
>Bas.
>
>
>
>
>>On January 13, 2003 at 16:38:57, Bas Hamstra wrote:
>>
>>>Nee, da's niks heb ik al gezien. Gooi maar weg, ha ha.
>>>
>>>
>>>
>>>
>>>
>>>On January 13, 2003 at 16:16:11, Sander de Zoete wrote:
>>>
>>>>Does anyone use reverse bitboards? I'm writing a new chess program "Preatorian",
>>>>which uses reverse bitboards. Up till now it looks good, but is still 10% slower
>>>>on capture generation than my 0x88 program "Shark". And Shark is slow, it must
>>>>say.
>>>>
>>>>I add some code to see if i'm doing it correct? What could be improved?
>>>>
>>>>//---------------------------------------------------------------------------
>>>>// Generate Rook Moves for Move List
>>>>// Bit Manipulation Trick for REVERSE Bitboard use
>>>>// BITBOARD x, y;
>>>>// y = x ^ (x - 4);
>>>>// Starting from bit 3 (4 = 0100) up, all bits are set to 1 until the
>>>>// first bit of x, which is 1. Also including this bit.
>>>>// eg. x = 0101 0011, y will be 0011 1100.
>>>>// Steps to use bit manipulation x ^ (x -2)
>>>>// 1. Shift allpieces bitboard to the right until the bit with the attacking
>>>>// piece is bit zero
>>>>// 2. Mask the rank/file (for offboard problems)
>>>>// (BITBOARD rank_mask = 0xFF; BITBOARD file_mask = 0x0101010101010101;)
>>>>// 3.1 Perform the bit manipulation
>>>>// 3.2 If file or diagonal: use file_mask/diagonal_mask again!
>>>>// 4.1 Shift back to the left
>>>>// 4.2 Use clear_right half of diagonal if bit 3 (int 4) is set to remove
>>>>// redundant/wrong squares in upper right corner
>>>>// 5 Result is attacks by piece without piece itself
>>>>// 6. Use same steps 1 - 5 for reverse bitboard
>>>>//---------------------------------------------------------------------------
>>>>void RookRankMoves(TBoard *pos, BITBOARD rooksqueen_bitboard, BITBOARD
>>>>all_pieces,
>>>> int reverse, BITBOARD capture_board, int capture )
>>>>{
>>>>BITBOARD h1_bitboard, h2_bitboard;
>>>>int sq_to, sq_fr;
>>>>
>>>>h1_bitboard = rq_bitboard;
>>>>while(h1_bitboard)
>>>>{ sq_fr = LSB(h1_bitboard);
>>>> h2_bitboard = all_pieces;
>>>> h2_bitboard = h2_bitboard>>sq_fr;
>>>> h2_bitboard = h2_bitboard ^ (h2_bitboard - 2);
>>>> h2_bitboard = h2_bitboard<<sq_fr;
>>>> h2_bitboard = h2_bitboard & (mask_rank_1<<(8*(sq_fr>>3))) ;
>>>> //h1_bitboard = Clear_LSB(h1_bitboard);
>>>> h1_bitboard ^= bit_mask[sq_fr];
>>>> // remove captures/own pieces from non capture board
>>>> if (capture)
>>>> h2_bitboard &= capture_board;
>>>> else
>>>> h2_bitboard &= ~all_pieces;
>>>> while(h2_bitboard)
>>>> { sq_to = LSB(h2_bitboard);
>>>> //h2_bitboard = Clear_LSB(h2_bitboard);
>>>> h2_bitboard ^= bit_mask[sq_to];
>>>> if (reverse)
>>>> AddMoveToList((63-sq_fr), (63-sq_to),
>>>> (pos->piece_on_square[(63-sq_fr)]>>2),
>>>> (pos->piece_on_square[(63-sq_to)]>>2), 0, 0, 0);
>>>> else
>>>> AddMoveToList(sq_fr, sq_to,
>>>> (pos->piece_on_square[sq_fr]>>2),
>>>> (pos->piece_on_square[sq_to]>>2), 0, 0, 0);
>>>> g_move_list_counter++;
>>>> }// while h2_board
>>>>}// while h1_board
>>>>}
>>>>
>>>>Thanks for any input,
>>>>Sander de Zoete
Hi Hamster,
It takes more than two minutes...doesn't it? I call you tommorow.
Sander.
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