X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fhistory.cpp;h=2bb3451048d3f6ed5be283e7824232698a29c9ba;hp=3cda37061d6d55a201413736323d927b24514158;hb=c835ee88535e138a4a5870f18a1cebab96476cf7;hpb=78246035499e277a7099b73bb96ac1e115643d61

diff --git a/src/history.cpp b/src/history.cpp
index 3cda3706..2bb34510 100644
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -42,6 +42,7 @@ History::History() { clear(); }
 
 void History::clear() {
   memset(history, 0, 2 * 8 * 64 * sizeof(int));
+  memset(maxStaticValueDelta, 0, 2 * 8 * 64 * sizeof(int));
 }
 
 
@@ -75,8 +76,12 @@ void History::failure(Piece p, Square to, Depth d) {
   assert(square_is_ok(to));
 
   history[p][to] -= int(d) * int(d);
-  if (history[p][to] < 0)
-      history[p][to] = 0;
+
+  // Prevent history underflow
+  if (history[p][to] <= -HistoryMax)
+      for (int i = 0; i < 16; i++)
+          for (int j = 0; j < 64; j++)
+              history[i][j] /= 2;
 }
 
 
@@ -90,3 +95,21 @@ int History::move_ordering_score(Piece p, Square to) const {
 
   return history[p][to];
 }
+
+
+/// History::set_gain() and History::gain() store and retrieve the
+/// gain of a move given the delta of the static position evaluations
+/// before and after the move.
+
+void History::set_gain(Piece p, Square to, Value delta)
+{
+  if (delta >= maxStaticValueDelta[p][to])
+      maxStaticValueDelta[p][to] = delta;
+  else
+      maxStaticValueDelta[p][to]--;
+}
+
+Value History::gain(Piece p, Square to) const
+{
+  return Value(maxStaticValueDelta[p][to]);
+}