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New simple and fast bitboard move generator
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Michael Sherwin



Joined: 26 May 2006
Posts: 2215
Location: OH, USA
PostPost subject: New simple and fast bitboard move generator    Posted: Sat May 05, 2007 3:52 pm Reply to topic Reply with quote
Code:
u32 RookIndex(u32 sq, u64 occ) {
    return = indexN[sq][FirstBit(occ & bitsN[sq])]
           | indexE[sq][FirstBit(occ & bitsE[sq])]
           | indexS[sq][LastBit (occ & bitsS[sq])]
           | indexW[sq][LastBit (occ & bitsW[sq])];
}


Since, bsf/bsr is very fast on core 2 this should be very competitive, in both 32 bit mode and 64 bit mode.

A rook on a1 only needs 3 bits + 3 bits = 6 bits of index, to hold the bit placements for the two directions. A rook on e4 needs 2 + 2 + 2 + 2 = 8 bits for the four directions. Remember not to include the final destination edge square.

This has the huge advantage that no 64 bit multiplication needs to be done and no shift back into place as well. Also it requires smaller lookup tables!

The returned index can be used to look up the mobility as well as the attack set.
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Regards,
Mike
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Subject Author Date/Time
New simple and fast bitboard move generator Michael Sherwin Sat May 05, 2007 3:52 pm
      Re: New simple and fast bitboard move generator Gerd Isenberg Sat May 05, 2007 5:43 pm
            Re: New simple and fast bitboard move generator Gerd Isenberg Sun May 06, 2007 8:52 am
                  Re: New simple and fast bitboard move generator Michael Sherwin Sun May 06, 2007 10:31 am
                        Re: New simple and fast bitboard move generator Gerd Isenberg Sun May 06, 2007 11:16 am
                              Re: New simple and fast bitboard move generator Michael Sherwin Sun May 06, 2007 1:21 pm
                                    Re: New simple and fast bitboard move generator Gerd Isenberg Sun May 06, 2007 1:52 pm
                                          Re: New simple and fast bitboard move generator Michael Sherwin Sun May 06, 2007 3:15 pm
                              Re: New simple and fast bitboard move generator Michael Sherwin Sun May 06, 2007 10:29 pm
                                    Re: New simple and fast bitboard move generator Gerd Isenberg Mon May 07, 2007 8:40 am
                                          Re: New simple and fast bitboard move generator Michael Sherwin Mon May 07, 2007 11:06 am
                                          Re: New simple and fast bitboard move generator Gerd Isenberg Mon May 07, 2007 8:08 pm
                                                Re: New simple and fast bitboard move generator Gerd Isenberg Mon May 07, 2007 11:22 pm
                                                      Re: New simple and fast bitboard move generator Michael Sherwin Tue May 08, 2007 3:18 am
                                                            Re: New simple and fast bitboard move generator Gerd Isenberg Tue May 08, 2007 6:11 am
                                                Re: New simple and fast bitboard move generator Michael Sherwin Tue May 08, 2007 9:25 pm
                                                      Re: New simple and fast bitboard move generator Michael Sherwin Tue May 08, 2007 10:55 pm
                                                      Re: New simple and fast bitboard move generator Gerd Isenberg Wed May 09, 2007 3:18 am
                                                            Re: New simple and fast bitboard move generator Tony Wed May 09, 2007 6:10 am
                                                                  Re: New simple and fast bitboard move generator Michael Sherwin Wed May 09, 2007 7:47 am
                                                                        Re: New simple and fast bitboard move generator Tony Wed May 09, 2007 8:24 am
                                                      Re: New simple and fast bitboard move generator Gerd Isenberg Wed May 09, 2007 7:31 pm
                                                            Re: New simple and fast bitboard move generator Michael Sherwin Wed May 09, 2007 11:30 pm
            Re: New simple and fast bitboard move generator Tony Mon May 07, 2007 6:46 am
                  Re: New simple and fast bitboard move generator Gerd Isenberg Mon May 07, 2007 8:51 am
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