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Rome-SPQR.JPG

Gullydeckel,
a free open source engine under the GNU General Public License written in C by Martin Borriss. Supported platforms are Linux and Windows. Gullydeckel is Chess Engine Communication Protocol compliant.

Gullydeckel's board representation relies on Piece-Lists and 0x88. Its search is plain alpha-beta using a recursive null move pruning with depth reduction R of 2.
Manhole cover in Rome [1]

0x88 Difference

The preinitialized static int vector[256] in "attacks.c" [2] with ray directions encoded, which is indexed by 0x88 square difference plus offset, somehow reminds on a Gullydeckel, the colloquial German name for Manhole cover [3]:
/*
if we find that two squares are related according to matrix SqRel,
we use another matrix to look up the direction of the move required
('to walk the vector') if it is a sliding piece (R,B,Q)
*/
 
static int vector[256] = {
   0  ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,UR,0 ,0 ,0 ,0 ,0 ,0 ,
   UP ,0 ,0 ,0 ,0 ,0 ,0 ,UL,0 ,0 ,UR,0 ,0 ,0 ,0 ,0 ,
   UP ,0 ,0 ,0 ,0 ,0 ,UL,0 ,0 ,0 ,0 ,UR,0 ,0 ,0 ,0 ,
   UP ,0 ,0 ,0 ,0 ,UL,0 ,0 ,0 ,0 ,0 ,0 ,UR,0 ,0 ,0 ,
   UP ,0 ,0 ,0 ,UL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,UR,0 ,0 ,
   UP ,0 ,0 ,UL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,UR,0 ,
   UP ,0 ,UL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,UR,
   UP ,UL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,RI,RI,RI,RI,RI,RI,RI,
   0  ,LE,LE,LE,LE,LE,LE,LE,0 ,0 ,0 ,0 ,0 ,0 ,0 ,DR,
   DN ,DL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,DR,0 ,
   DN ,0 ,DL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,DR,0 ,0 ,
   DN ,0 ,0 ,DL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0 ,DR,0 ,0 ,0 ,
   DN ,0 ,0 ,0 ,DL,0 ,0 ,0 ,0 ,0 ,0 ,DR,0 ,0 ,0 ,0 ,
   DN ,0 ,0 ,0 ,0 ,DL,0 ,0 ,0 ,0 ,DR,0 ,0 ,0 ,0 ,0 ,
   DN ,0 ,0 ,0 ,0 ,0 ,DL,0 ,0 ,DR,0 ,0 ,0 ,0 ,0 ,0 ,
   DN ,0 ,0 ,0 ,0 ,0 ,0 ,DL,0 ,0 ,0 ,0 ,0 ,0 ,0 ,0
 };

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References

  1. ^ Manhole cover in Rome with SPQR inscription, Image by Indian Joe, January 08, 2007, Wikimedia Commons, SPQR from Wikipedia
  2. ^ Gullydeckel Chess Program - Download
  3. ^ edited, symbols replaced for column alignment

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