Combination of two ideas:

Apply bonus for the prior CMH that caused a fail low.

Balance Stats: CMH and History bonuses are updated differently.
This eliminates the "fudge" factor weight when scoring moves. Also
eliminated discontinuity in the gravity history stat formula. (i.e. stat
scores will no longer inverse when depth exceeds 22)

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 21802 W: 4107 L: 3887 D: 13808

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 46036 W: 7046 L: 6756 D: 32234

Bench: 7677367

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 3d44721b687059b9f8a284759112f7299732a0f4..7cf3e60723206324a1ec24b8b886c1b8b4d60bba 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -146,7 +146,7 @@ void MovePicker::score<QUIETS>() {
 
   for (auto& m : *this)
       m.value =  history[pos.moved_piece(m)][to_sq(m)]
 
   for (auto& m : *this)
       m.value =  history[pos.moved_piece(m)][to_sq(m)]

-               + cmh[pos.moved_piece(m)][to_sq(m)] * 3;
+               + cmh[pos.moved_piece(m)][to_sq(m)];

 }
 
 template<>
 }
 
 template<>

diff --git a/src/movepick.h b/src/movepick.h
index e64ebfade18308a55046c7b61e396e1800bb7f75..b488313a446833db0b5a8a2d1e8a3fa495964252 100644 (file)
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -39,7 +39,7 @@
 template<typename T>
 struct Stats {
 
 template<typename T>
 struct Stats {
 

-  static const Value Max = Value(1 << 28);
+  static const Value Max = Value(1<<28);

 
   const T* operator[](Piece pc) const { return table[pc]; }
   T* operator[](Piece pc) { return table[pc]; }
 
   const T* operator[](Piece pc) const { return table[pc]; }
   T* operator[](Piece pc) { return table[pc]; }


@@ -51,10 +51,20 @@ struct Stats {
         table[pc][to] = m;
   }
 
         table[pc][to] = m;
   }
 

-  void update(Piece pc, Square to, Value v) {
+  void updateH(Piece pc, Square to, Value v) {

 
 

-    table[pc][to] -= table[pc][to] * std::min(abs(v), 512) / 512;
-    table[pc][to] += v * 64;
+    if (abs(int(v)) >= 324) 
+        return;
+    table[pc][to] -= table[pc][to] * abs(int(v)) / 324;
+    table[pc][to] += int(v) * 32;
+  }
+
+  void updateCMH(Piece pc, Square to, Value v) {
+
+    if (abs(int(v)) >= 324) 
+        return;
+    table[pc][to] -= table[pc][to] * abs(int(v)) / 512;
+    table[pc][to] += int(v) * 64;

   }
 
 private:
   }
 
 private:

diff --git a/src/search.cpp b/src/search.cpp
index efcbdef00a52a9d37a1dc982f937b5ea7460588c..4988dc8e67695fa9251cf23a55211e023d07032d 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1132,6 +1132,19 @@ moves_loop: // When in check and at SpNode search starts from here
     else if (bestMove && !pos.capture_or_promotion(bestMove))
         update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount);
 
     else if (bestMove && !pos.capture_or_promotion(bestMove))
         update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount);
 

+    // Bonus for prior countermove that caused the fail low
+    else if (!bestMove)
+    {
+        if (is_ok((ss - 2)->currentMove) && is_ok((ss - 1)->currentMove) && !pos.captured_piece_type() && !inCheck && depth>=3*ONE_PLY)
+        {
+            Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY));
+            Square prevSq = to_sq((ss - 1)->currentMove);
+            Square prevPrevSq = to_sq((ss - 2)->currentMove);
+            HistoryStats& flMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
+            flMoveCmh.updateCMH(pos.piece_on(prevSq), prevSq, bonus);
+        }
+    }
+

     tte->save(posKey, value_to_tt(bestValue, ss->ply),
               bestValue >= beta ? BOUND_LOWER :
               PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
     tte->save(posKey, value_to_tt(bestValue, ss->ply),
               bestValue >= beta ? BOUND_LOWER :
               PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,


@@ -1405,21 +1418,21 @@ moves_loop: // When in check and at SpNode search starts from here
     Square prevSq = to_sq((ss-1)->currentMove);
     HistoryStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
 
     Square prevSq = to_sq((ss-1)->currentMove);
     HistoryStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
 

-    History.update(pos.moved_piece(move), to_sq(move), bonus);
+    History.updateH(pos.moved_piece(move), to_sq(move), bonus);

 
     if (is_ok((ss-1)->currentMove))
     {
         Countermoves.update(pos.piece_on(prevSq), prevSq, move);
 
     if (is_ok((ss-1)->currentMove))
     {
         Countermoves.update(pos.piece_on(prevSq), prevSq, move);

-        cmh.update(pos.moved_piece(move), to_sq(move), bonus);
+        cmh.updateCMH(pos.moved_piece(move), to_sq(move), bonus);

     }
 
     // Decrease all the other played quiet moves
     for (int i = 0; i < quietsCnt; ++i)
     {
     }
 
     // Decrease all the other played quiet moves
     for (int i = 0; i < quietsCnt; ++i)
     {

-        History.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+        History.updateH(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);

 
         if (is_ok((ss-1)->currentMove))
 
         if (is_ok((ss-1)->currentMove))

-            cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+            cmh.updateCMH(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);

     }
 
     // Extra penalty for PV move in previous ply when it gets refuted
     }
 
     // Extra penalty for PV move in previous ply when it gets refuted


@@ -1427,7 +1440,7 @@ moves_loop: // When in check and at SpNode search starts from here
     {
         Square prevPrevSq = to_sq((ss-2)->currentMove);
         HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
     {
         Square prevPrevSq = to_sq((ss-2)->currentMove);
         HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];

-        ttMoveCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * depth / ONE_PLY - 1);
+        ttMoveCmh.updateCMH(pos.piece_on(prevSq), prevSq, -bonus - 2 * depth / ONE_PLY - 1);

     }
   }
 
     }
   }