Simplify stats update

Simplify code by moving countermove and follow-up move
history update into procedure.

No functional change.

src/search.cpp

@@ -168,8 +168,8 @@ namespace {
   Value value_to_tt(Value v, int ply);
   Value value_from_tt(Value v, int ply);
   void update_pv(Move* pv, Move move, Move* childPv);
+  void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus);
   void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus);
-  void update_opponent_stats(const Position& pos, Stack* ss, Value bonus);
   void check_time();
 
 } // namespace
@@ -651,7 +651,8 @@ namespace {
             if ((ss-1)->moveCount == 1 && !pos.captured_piece_type())
             {
                 Value penalty = Value(d * d + 4 * d + 1);
-                update_opponent_stats(pos, ss, -penalty);
+                Square prevSq = to_sq((ss-1)->currentMove);
+                update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
             }
         }
         return ttValue;
@@ -1141,7 +1142,8 @@ namespace {
         if ((ss-1)->moveCount == 1 && !pos.captured_piece_type())
         {
             Value penalty = Value(d * d + 4 * d + 1);
-            update_opponent_stats(pos, ss, -penalty);
+            Square prevSq = to_sq((ss-1)->currentMove);
+            update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
         }
     }
     // Bonus for prior countermove that caused the fail low
@@ -1151,7 +1153,8 @@ namespace {
     {
         int d = depth / ONE_PLY;
         Value bonus = Value(d * d + 2 * d - 2);
-        update_opponent_stats(pos, ss, bonus);
+        Square prevSq = to_sq((ss-1)->currentMove);
+        update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus);
     }
 
     tte->save(posKey, value_to_tt(bestValue, ss->ply),
@@ -1411,25 +1414,22 @@ namespace {
   }
 
 
-  // update_opponent_stats() updates countermoves for prior opponent move, i.e.
-  // (ss-1)->currentMove. Called for both capture and non-capture moves.
-
-  void update_opponent_stats(const Position& pos, Stack* ss, Value bonus) {
+  // update_cm_stats() updates countermove and follow-up move history
 
-    Square prevSq = to_sq((ss-1)->currentMove);
+  void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) {
 
-    CounterMoveStats* cmh  = (ss-2)->counterMoves;
-    CounterMoveStats* fmh1 = (ss-3)->counterMoves;
-    CounterMoveStats* fmh2 = (ss-5)->counterMoves;
+    CounterMoveStats* cmh  = (ss-1)->counterMoves;
+    CounterMoveStats* fmh1 = (ss-2)->counterMoves;
+    CounterMoveStats* fmh2 = (ss-4)->counterMoves;
 
     if (cmh)
-        cmh->update(pos.piece_on(prevSq), prevSq, bonus);
+        cmh->update(pc, s, bonus);
 
     if (fmh1)
-        fmh1->update(pos.piece_on(prevSq), prevSq, bonus);
+        fmh1->update(pc, s, bonus);
 
     if (fmh2)
-        fmh2->update(pos.piece_on(prevSq), prevSq, bonus);
+        fmh2->update(pc, s, bonus);
   }
 
 
@@ -1445,42 +1445,24 @@ namespace {
         ss->killers[0] = move;
     }
 
-    CounterMoveStats* cmh  = (ss-1)->counterMoves;
-    CounterMoveStats* fmh1 = (ss-2)->counterMoves;
-    CounterMoveStats* fmh2 = (ss-4)->counterMoves;
-
     Color c = pos.side_to_move();
     Thread* thisThread = pos.this_thread();
-    thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);
     thisThread->fromTo.update(c, move, bonus);
+    thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);
+    update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus);
 
-    if (cmh)
+    if ((ss-1)->counterMoves)
     {
         Square prevSq = to_sq((ss-1)->currentMove);
         thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move);
-        cmh->update(pos.moved_piece(move), to_sq(move), bonus);
     }
 
-    if (fmh1)
-        fmh1->update(pos.moved_piece(move), to_sq(move), bonus);
-
-    if (fmh2)
-        fmh2->update(pos.moved_piece(move), to_sq(move), bonus);
-
     // Decrease all the other played quiet moves
     for (int i = 0; i < quietsCnt; ++i)
     {
-        thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
         thisThread->fromTo.update(c, quiets[i], -bonus);
-
-        if (cmh)
-            cmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
-
-        if (fmh1)
-            fmh1->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
-
-        if (fmh2)
-            fmh2->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+        thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+        update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
     }
   }