Implement MaxGain table

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

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];
+}