Halve PSQT row data

Use symmetry along vertical middle axis of the board
to reduce the number of parameters.

For instance psqt value of SQ_A5 == SQ_A4 and value of
SQ_F8 == SQ_F1.

This is always true, at least until now nobody came in
with an asymmetric psqt table that worked.

Original patch by Lucas.

No functional change.

diff --git a/src/psqt.cpp b/src/psqt.cpp
index 32601c0a56cafbdaddc2f1f2e23f5582c0eb9eae..3d06a07c0c46029130982e024e4ebbb7ea80795f 100644 (file)
--- a/src/psqt.cpp
+++ b/src/psqt.cpp
@@ -23,70 +23,71 @@ namespace PSQT {
 
 #define S(mg, eg) make_score(mg, eg)
 
-/// BaseTable[PieceType][Square] contains Piece-Square scores. For each piece
-/// type on a given square a (middlegame, endgame) score pair is assigned. Table
-/// is defined just for the white side; it is symmetric for the black side.
-const Score BaseTable[][SQUARE_NB] = {
+// Bonus[PieceType][Square / 2] contains Piece-Square scores. For each piece
+// type on a given square a (middlegame, endgame) score pair is assigned. Table
+// is defined for files A..D and white side: it is symmetric for black side and
+// second half of the files.
+const Score Bonus[][int(SQUARE_NB) / 2] = {
   { },
   { // Pawn
-   S(  0, 0), S(  0, 0), S( 0, 0), S( 0, 0), S( 0, 0), S( 0, 0), S(  0, 0), S(  0, 0),
-   S(-22, 4), S(  3,-6), S( 7, 8), S( 3,-1), S( 3,-1), S( 7, 8), S(  3,-6), S(-22, 4),
-   S(-25,-3), S( -7,-4), S(18, 4), S(24, 5), S(24, 5), S(18, 4), S( -7,-4), S(-25,-3),
-   S(-27, 1), S(-15, 2), S(15,-8), S(30,-2), S(30,-2), S(15,-8), S(-15, 2), S(-27, 1),
-   S(-14, 7), S(  0,12), S(-2, 4), S(18,-3), S(18,-3), S(-2, 4), S(  0,12), S(-14, 7),
-   S(-12, 8), S(-13,-5), S(-6, 1), S(-4, 7), S(-4, 7), S(-6, 1), S(-13,-5), S(-12, 8),
-   S(-17, 1), S( 10,-9), S(-4, 1), S(-6,16), S(-6,16), S(-4, 1), S( 10,-9), S(-17, 1),
-   S(  0, 0), S(  0, 0), S( 0, 0), S( 0, 0), S( 0, 0), S( 0, 0), S(  0, 0), S(  0, 0)
+   S(  0, 0), S(  0, 0), S( 0, 0), S( 0, 0),
+   S(-22, 4), S(  3,-6), S( 7, 8), S( 3,-1),
+   S(-25,-3), S( -7,-4), S(18, 4), S(24, 5),
+   S(-27, 1), S(-15, 2), S(15,-8), S(30,-2),
+   S(-14, 7), S(  0,12), S(-2, 4), S(18,-3),
+   S(-12, 8), S(-13,-5), S(-6, 1), S(-4, 7),
+   S(-17, 1), S( 10,-9), S(-4, 1), S(-6,16),
+   S(  0, 0), S(  0, 0), S( 0, 0), S( 0, 0)
   },
   { // Knight
-   S(-144,-98), S(-109,-83), S(-85,-51), S(-73,-16), S(-73,-16), S(-85,-51), S(-109,-83), S(-144,-98),
-   S( -88,-68), S( -43,-53), S(-19,-21), S( -7, 14), S( -7, 14), S(-19,-21), S( -43,-53), S( -88,-68),
-   S( -69,-53), S( -24,-38), S(  0, -6), S( 12, 29), S( 12, 29), S(  0, -6), S( -24,-38), S( -69,-53),
-   S( -28,-42), S(  17,-27), S( 41,  5), S( 53, 40), S( 53, 40), S( 41,  5), S(  17,-27), S( -28,-42),
-   S( -30,-42), S(  15,-27), S( 39,  5), S( 51, 40), S( 51, 40), S( 39,  5), S(  15,-27), S( -30,-42),
-   S( -10,-53), S(  35,-38), S( 59, -6), S( 71, 29), S( 71, 29), S( 59, -6), S(  35,-38), S( -10,-53),
-   S( -64,-68), S( -19,-53), S(  5,-21), S( 17, 14), S( 17, 14), S(  5,-21), S( -19,-53), S( -64,-68),
-   S(-200,-98), S( -65,-83), S(-41,-51), S(-29,-16), S(-29,-16), S(-41,-51), S( -65,-83), S(-200,-98)
+   S(-144,-98), S(-109,-83), S(-85,-51), S(-73,-16),
+   S( -88,-68), S( -43,-53), S(-19,-21), S( -7, 14),
+   S( -69,-53), S( -24,-38), S(  0, -6), S( 12, 29),
+   S( -28,-42), S(  17,-27), S( 41,  5), S( 53, 40),
+   S( -30,-42), S(  15,-27), S( 39,  5), S( 51, 40),
+   S( -10,-53), S(  35,-38), S( 59, -6), S( 71, 29),
+   S( -64,-68), S( -19,-53), S(  5,-21), S( 17, 14),
+   S(-200,-98), S( -65,-83), S(-41,-51), S(-29,-16)
   },
   { // Bishop
-   S(-54,-65), S(-27,-42), S(-34,-44), S(-43,-26), S(-43,-26), S(-34,-44), S(-27,-42), S(-54,-65),
-   S(-29,-43), S(  8,-20), S(  1,-22), S( -8, -4), S( -8, -4), S(  1,-22), S(  8,-20), S(-29,-43),
-   S(-20,-33), S( 17,-10), S( 10,-12), S(  1,  6), S(  1,  6), S( 10,-12), S( 17,-10), S(-20,-33),
-   S(-19,-35), S( 18,-12), S( 11,-14), S(  2,  4), S(  2,  4), S( 11,-14), S( 18,-12), S(-19,-35),
-   S(-22,-35), S( 15,-12), S(  8,-14), S( -1,  4), S( -1,  4), S(  8,-14), S( 15,-12), S(-22,-35),
-   S(-28,-33), S(  9,-10), S(  2,-12), S( -7,  6), S( -7,  6), S(  2,-12), S(  9,-10), S(-28,-33),
-   S(-32,-43), S(  5,-20), S( -2,-22), S(-11, -4), S(-11, -4), S( -2,-22), S(  5,-20), S(-32,-43),
-   S(-49,-65), S(-22,-42), S(-29,-44), S(-38,-26), S(-38,-26), S(-29,-44), S(-22,-42), S(-49,-65)
+   S(-54,-65), S(-27,-42), S(-34,-44), S(-43,-26),
+   S(-29,-43), S(  8,-20), S(  1,-22), S( -8, -4),
+   S(-20,-33), S( 17,-10), S( 10,-12), S(  1,  6),
+   S(-19,-35), S( 18,-12), S( 11,-14), S(  2,  4),
+   S(-22,-35), S( 15,-12), S(  8,-14), S( -1,  4),
+   S(-28,-33), S(  9,-10), S(  2,-12), S( -7,  6),
+   S(-32,-43), S(  5,-20), S( -2,-22), S(-11, -4),
+   S(-49,-65), S(-22,-42), S(-29,-44), S(-38,-26)
   },
   { // Rook
-   S(-22, 3), S(-17, 3), S(-12, 3), S(-8, 3), S(-8, 3), S(-12, 3), S(-17, 3), S(-22, 3),
-   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3), S( 2, 3), S( -2, 3), S( -7, 3), S(-22, 3),
-   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3), S( 2, 3), S( -2, 3), S( -7, 3), S(-22, 3),
-   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3), S( 2, 3), S( -2, 3), S( -7, 3), S(-22, 3),
-   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3), S( 2, 3), S( -2, 3), S( -7, 3), S(-22, 3),
-   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3), S( 2, 3), S( -2, 3), S( -7, 3), S(-22, 3),
-   S(-11, 3), S(  4, 3), S(  9, 3), S(13, 3), S(13, 3), S(  9, 3), S(  4, 3), S(-11, 3),
-   S(-22, 3), S(-17, 3), S(-12, 3), S(-8, 3), S(-8, 3), S(-12, 3), S(-17, 3), S(-22, 3)
+   S(-22, 3), S(-17, 3), S(-12, 3), S(-8, 3),
+   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3),
+   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3),
+   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3),
+   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3),
+   S(-22, 3), S( -7, 3), S( -2, 3), S( 2, 3),
+   S(-11, 3), S(  4, 3), S(  9, 3), S(13, 3),
+   S(-22, 3), S(-17, 3), S(-12, 3), S(-8, 3)
   },
   { // Queen
-   S(-2,-80), S(-2,-54), S(-2,-42), S(-2,-30), S(-2,-30), S(-2,-42), S(-2,-54), S(-2,-80),
-   S(-2,-54), S( 8,-30), S( 8,-18), S( 8, -6), S( 8, -6), S( 8,-18), S( 8,-30), S(-2,-54),
-   S(-2,-42), S( 8,-18), S( 8, -6), S( 8,  6), S( 8,  6), S( 8, -6), S( 8,-18), S(-2,-42),
-   S(-2,-30), S( 8, -6), S( 8,  6), S( 8, 18), S( 8, 18), S( 8,  6), S( 8, -6), S(-2,-30),
-   S(-2,-30), S( 8, -6), S( 8,  6), S( 8, 18), S( 8, 18), S( 8,  6), S( 8, -6), S(-2,-30),
-   S(-2,-42), S( 8,-18), S( 8, -6), S( 8,  6), S( 8,  6), S( 8, -6), S( 8,-18), S(-2,-42),
-   S(-2,-54), S( 8,-30), S( 8,-18), S( 8, -6), S( 8, -6), S( 8,-18), S( 8,-30), S(-2,-54),
-   S(-2,-80), S(-2,-54), S(-2,-42), S(-2,-30), S(-2,-30), S(-2,-42), S(-2,-54), S(-2,-80)
+   S(-2,-80), S(-2,-54), S(-2,-42), S(-2,-30),
+   S(-2,-54), S( 8,-30), S( 8,-18), S( 8, -6),
+   S(-2,-42), S( 8,-18), S( 8, -6), S( 8,  6),
+   S(-2,-30), S( 8, -6), S( 8,  6), S( 8, 18),
+   S(-2,-30), S( 8, -6), S( 8,  6), S( 8, 18),
+   S(-2,-42), S( 8,-18), S( 8, -6), S( 8,  6),
+   S(-2,-54), S( 8,-30), S( 8,-18), S( 8, -6),
+   S(-2,-80), S(-2,-54), S(-2,-42), S(-2,-30)
   },
   { // King
-   S(298, 27), S(332, 81), S(273,108), S(225,116), S(225,116), S(273,108), S(332, 81), S(298, 27),
-   S(287, 74), S(321,128), S(262,155), S(214,163), S(214,163), S(262,155), S(321,128), S(287, 74),
-   S(224,111), S(258,165), S(199,192), S(151,200), S(151,200), S(199,192), S(258,165), S(224,111),
-   S(196,135), S(230,189), S(171,216), S(123,224), S(123,224), S(171,216), S(230,189), S(196,135),
-   S(173,135), S(207,189), S(148,216), S(100,224), S(100,224), S(148,216), S(207,189), S(173,135),
-   S(146,111), S(180,165), S(121,192), S( 73,200), S( 73,200), S(121,192), S(180,165), S(146,111),
-   S(119, 74), S(153,128), S( 94,155), S( 46,163), S( 46,163), S( 94,155), S(153,128), S(119, 74),
-   S( 98, 27), S(132, 81), S( 73,108), S( 25,116), S( 25,116), S( 73,108), S(132, 81), S( 98, 27)
+   S(298, 27), S(332, 81), S(273,108), S(225,116),
+   S(287, 74), S(321,128), S(262,155), S(214,163),
+   S(224,111), S(258,165), S(199,192), S(151,200),
+   S(196,135), S(230,189), S(171,216), S(123,224),
+   S(173,135), S(207,189), S(148,216), S(100,224),
+   S(146,111), S(180,165), S(121,192), S( 73,200),
+   S(119, 74), S(153,128), S( 94,155), S( 46,163),
+   S( 98, 27), S(132, 81), S( 73,108), S( 25,116)
   }
 };
 
@@ -95,7 +96,7 @@ const Score BaseTable[][SQUARE_NB] = {
 Score psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB];
 
 // init() initializes piece square tables: the white halves of the tables are
-// copied from BaseTable[] adding the piece value, then the black halves of the
+// copied from Bonus[] adding the piece value, then the black halves of the
 // tables are initialized by flipping and changing the sign of the white scores.
 void init() {
 
@@ -107,7 +108,11 @@ void init() {
       Score v = make_score(PieceValue[MG][pt], PieceValue[EG][pt]);
 
       for (Square s = SQ_A1; s <= SQ_H8; ++s)
-          psq[BLACK][pt][~s] = -(psq[WHITE][pt][ s] = (v + BaseTable[pt][s]));
+      {
+          // Flip to the left half of the board and subtract 4 for each rank
+          int ss = (file_of(s) < FILE_E ? s : s ^ 7) - 4 * rank_of(s);
+          psq[BLACK][pt][~s] = -(psq[WHITE][pt][s] = v + Bonus[pt][ss]);
+      }
   }
 }