Limit history range to +-2000

Extensive test series on tweaking history limit and bonus
formula. At the end this was the best.

After 11959 games:

Mod vs Orig 2087 - 1934 - 7938 ELO +4 (+- 3.7) LOS 92%

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

diff --git a/src/history.h b/src/history.h
index 0f3fbc10405e8789219c2af0ff1d294ec1263522..4d84be7054858eb37407b097b87e5aa2320e7846 100644 (file)
--- a/src/history.h
+++ b/src/history.h
@@ -39,7 +39,7 @@ public:
   Value gain(Piece p, Square to) const;
   void update_gain(Piece p, Square to, Value g);
 
-  static const Value MaxValue = Value(1 << 29); // To avoid an overflow
+  static const Value MaxValue = Value(2000);
 
 private:
   Value history[16][64];  // [piece][to_square]