Walter+Faxon

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 * Walter Faxon** from the United States is one of the bitscan pioneers. His magic bitscan, invented in the 80s is still one of the most competitive on 32-bit architectures . On June 09, 2003 Walter made a thought-provoking appeal in CCC.

=Magic Bitscan= Walter Faxon's 32-bit friendly magic bitscan uses a fast none minimal perfect hashing function: code format="cpp" const char LSB_64_table[154] = {  22,__,__,__,30,__,__,38,18,__, 16,15,17,__,46, 9,19, 8, 7,10,   0, 63, 1,56,55,57, 2,11,__,58, __,__,20,__, 3,__,__,59,__,__,   __,__,__,12,__,__,__,__,__,__, 4,__,__,60,__,__,__,__,__,__,   __,__,__,__,21,__,__,__,29,__, __,37,__,__,__,13,__,__,45,__,   __,__, 5,__,__,61,__,__,__,53, __,__,__,__,__,__,__,__,__,__,   28,__,__,36,__,__,__,__,__,__, 44,__,__,__,__,__,27,__,__,35,   __,52,__,__,26,__,43,34,25,23, 24,33,31,32,42,39,40,51,41,14,   __,49,47,48,__,50, 6,__,__,62, __,__,__,54 };
 * 1) define __ 0
 * 1) undef __

/** * bitScanForward * @author Walter Faxon, slightly modified * @param bb bitboard to scan * @precondition bb != 0 * @return index (0..63) of least significant one bit */ int bitScanForward(U64 bb) {  unsigned int t32; assert(bb); bb ^= bb - 1; t32 = (int)bb ^ (int)(bb >> 32); t32 ^= 0x01C5FC81; t32 += t32 >> 16; t32 -= (t32 >> 8) + 51; return LSB_64_table [t32 & 255]; // 0..63 } code

=Markoff - Botvinnik - Kaissa - Hsu - ABC - Berliner=

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=No Go= (was Re: Markoff -- Botvinnik -- Kaissa -- Hsu -- ABC -- Berliner)

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=Forum Posts=
 * [|Another hacky method for bitboard bit extraction] by Walter Faxon, CCC, November 17, 2002
 * [|Re: Beating Bitscan to Death -- yet again] by Walter Faxon, CCC, December 30, 2002
 * [|Re: Computer Chess Went The Wrong Way...] by Walter Faxon, CCC, January 07, 2003
 * [|Markoff - Botvinnik - Kaissa - Hsu - ABC - Berliner] by Walter Faxon, CCC, June 09, 2003
 * [|Old chess program in BASIC (long post)] by Walter Faxon, CCC, March 20, 2005 » Basic
 * [|(Obvious troll) Kasparov vs DB-I was a disaster for human chess] by Walter Faxon, CCC, May 06, 2005 » Deep Blue

=References= =What links here?= include page="Walter Faxon" component="backlinks" limit="40"
 * Up one level**