Implement MaxGain table

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/Makefile

@@ -68,7 +68,7 @@ LDFLAGS  = -lpthread
 OBJS = application.o bitboard.o pawns.o material.o endgame.o evaluate.o main.o \
 	misc.o move.o movegen.o history.o movepick.o search.o piece.o \
 	position.o direction.o tt.o value.o uci.o ucioption.o \
-	mersenne.o book.o bitbase.o san.o benchmark.o
+	maxgain.o mersenne.o book.o bitbase.o san.o benchmark.o
 
 
 ### General rules. Do not change

src/maxgain.cpp

@@ -0,0 +1,67 @@
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2009 Marco Costalba
+
+  Stockfish is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Stockfish is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+////
+//// Includes
+////
+
+#include <cassert>
+#include <cstring>
+
+#include "maxgain.h"
+#include "value.h"
+
+////
+//// Functions
+////
+
+
+/// Constructor
+
+MaxGain::MaxGain() { clear(); }
+
+
+/// MaxGain::clear() clears the table
+
+void MaxGain::clear() {
+  memset(maxStaticValueDelta, 0, 16 * 64 * 64 * sizeof(int));
+}
+
+
+/// MaxGain::store
+
+void MaxGain::store(Piece p, Square from, Square to, Value prev, Value curr)
+{
+  if (prev == VALUE_NONE || curr == VALUE_NONE)
+    return;
+
+  Value delta = curr - prev;
+  if (delta >= maxStaticValueDelta[p][from][to])
+    maxStaticValueDelta[p][from][to] = delta;
+  else
+    maxStaticValueDelta[p][from][to]--;
+}
+
+// MaxGain::retrieve
+
+Value MaxGain::retrieve(Piece p, Square from, Square to)
+{
+  return (Value) maxStaticValueDelta[p][from][to];
+}

src/maxgain.h

@@ -0,0 +1,51 @@
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2009 Marco Costalba
+
+  Stockfish is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Stockfish is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#if !defined(MAXGAIN_H_INCLUDED)
+#define MAXGAIN_H_INCLUDED
+
+////
+//// Includes
+////
+
+#include "move.h"
+#include "piece.h"
+#include "value.h"
+
+
+////
+//// Types
+////
+
+class MaxGain {
+
+public:
+  MaxGain();
+  void clear();
+  void store(Piece p, Square from, Square to, Value prev, Value curr);
+  Value retrieve(Piece p, Square from, Square to);
+
+private:
+  int maxStaticValueDelta[16][64][64];  // [piece][from_square][to_square]
+};
+
+
+#endif // !defined(MAXGAIN_H_INCLUDED)
+

src/position.cpp

@@ -1301,6 +1301,11 @@ void Position::undo_null_move() {
 }
 
 
+///
+PieceType Position::captured_piece() const {
+  return st->capture;
+}
+
 /// Position::see() is a static exchange evaluator: It tries to estimate the
 /// material gain or loss resulting from a move. There are three versions of
 /// this function: One which takes a destination square as input, one takes a

src/position.h

@@ -241,6 +241,9 @@ public:
   void do_null_move(StateInfo& st);
   void undo_null_move();
 
+  // Past
+  PieceType captured_piece() const;
+
   // Static exchange evaluation
   int see(Square from, Square to) const;
   int see(Move m) const;

src/search.cpp

@@ -32,6 +32,7 @@
 #include "book.h"
 #include "evaluate.h"
 #include "history.h"
+#include "maxgain.h"
 #include "misc.h"
 #include "movegen.h"
 #include "movepick.h"
@@ -263,6 +264,8 @@ namespace {
   // History table
   History H;
 
+  // MaxGain table
+  MaxGain MG;
 
   /// Functions