Convert gains to use a piece-to mapping

[stockfish] / src / history.cpp

diff --git a/src/history.cpp b/src/history.cpp
index 6fe222feb4dfe7bec169d177bbb4b985ff350bc7..2bb3451048d3f6ed5be283e7824232698a29c9ba 100644 (file)
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -42,8 +42,7 @@ History::History() { clear(); }
 
 void History::clear() {
   memset(history, 0, 2 * 8 * 64 * sizeof(int));
-  memset(successCount, 0, 2 * 8 * 64 * sizeof(int));
-  memset(failureCount, 0, 2 * 8 * 64 * sizeof(int));
+  memset(maxStaticValueDelta, 0, 2 * 8 * 64 * sizeof(int));
 }
 
 
@@ -58,7 +57,6 @@ void History::success(Piece p, Square to, Depth d) {
   assert(square_is_ok(to));
 
   history[p][to] += int(d) * int(d);
-  successCount[p][to]++;
 
   // Prevent history overflow
   if (history[p][to] >= HistoryMax)
@@ -72,12 +70,18 @@ void History::success(Piece p, Square to, Depth d) {
 /// called for each non-capturing move which failed to produce a beta cutoff
 /// at a node where a beta cutoff was finally found.
 
-void History::failure(Piece p, Square to) {
+void History::failure(Piece p, Square to, Depth d) {
 
   assert(piece_is_ok(p));
   assert(square_is_ok(to));
 
-  failureCount[p][to]++;
+  history[p][to] -= int(d) * int(d);
+
+  // 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;
 }
 
 
@@ -93,13 +97,19 @@ int History::move_ordering_score(Piece p, Square to) const {
 }
 
 
-/// History::ok_to_prune() decides whether a move has been sufficiently
-/// unsuccessful that it makes sense to prune it entirely.
+/// 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.
 
-bool History::ok_to_prune(Piece p, Square to, Depth d) const {
-
-  assert(piece_is_ok(p));
-  assert(square_is_ok(to));
+void History::set_gain(Piece p, Square to, Value delta)
+{
+  if (delta >= maxStaticValueDelta[p][to])
+      maxStaticValueDelta[p][to] = delta;
+  else
+      maxStaticValueDelta[p][to]--;
+}
 
-  return (int(d) * successCount[p][to] < failureCount[p][to]);
+Value History::gain(Piece p, Square to) const
+{
+  return Value(maxStaticValueDelta[p][to]);
 }