Refactor bonus and penalty calculation (#917)

* Refactor bonus and penalty calculation

Compute common terms in a helper function.

No functional change.

* Further refactoring

Remove some parenthesis that are now useless.
Define prevSq once, use repeatedly.

No functional change.

bench: 5884767 (bench of previous patch is wrong)

src/search.cpp

@@ -153,6 +153,9 @@ namespace {
     {1, 0, 0, 0, 0, 1, 1 ,1},
   };
 
+  Value bonus(Depth depth)   { int d = depth / ONE_PLY ; return  Value(d * d + 2 * d - 2); }
+  Value penalty(Depth depth) { int d = depth / ONE_PLY ; return -Value(d * d + 4 * d + 1); }
+
   const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
 
   EasyMoveManager EasyMove;
@@ -616,6 +619,7 @@ namespace {
     ss->counterMoves = nullptr;
     (ss+1)->skipEarlyPruning = false;
     (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+    Square prevSq = to_sq((ss-1)->currentMove);
 
     // Step 4. Transposition table lookup. We don't want the score of a partial
     // search to overwrite a previous full search TT value, so we use a different
@@ -638,21 +642,12 @@ namespace {
         // If ttMove is quiet, update killers, history, counter move on TT hit
         if (ttValue >= beta && ttMove)
         {
-            int d = depth / ONE_PLY;
-
             if (!pos.capture_or_promotion(ttMove))
-            {
-                Value bonus = Value(d * d + 2 * d - 2);
-                update_stats(pos, ss, ttMove, nullptr, 0, bonus);
-            }
+                update_stats(pos, ss, ttMove, nullptr, 0, bonus(depth));
 
             // Extra penalty for a quiet TT move in previous ply when it gets refuted
             if ((ss-1)->moveCount == 1 && !pos.captured_piece())
-            {
-                Value penalty = Value(d * d + 4 * d + 1);
-                Square prevSq = to_sq((ss-1)->currentMove);
-                update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
-            }
+                update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth));
         }
         return ttValue;
     }
@@ -1140,33 +1135,20 @@ namespace {
                    :     inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
     else if (bestMove)
     {
-        int d = depth / ONE_PLY;
 
         // Quiet best move: update killers, history and countermoves
         if (!pos.capture_or_promotion(bestMove))
-        {
-            Value bonus = Value(d * d + 2 * d - 2);
-            update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus);
-        }
+            update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus(depth));
 
         // Extra penalty for a quiet TT move in previous ply when it gets refuted
         if ((ss-1)->moveCount == 1 && !pos.captured_piece())
-        {
-            Value penalty = Value(d * d + 4 * d + 1);
-            Square prevSq = to_sq((ss-1)->currentMove);
-            update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
-        }
+            update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth));
     }
     // Bonus for prior countermove that caused the fail low
     else if (    depth >= 3 * ONE_PLY
              && !pos.captured_piece()
              && is_ok((ss-1)->currentMove))
-    {
-        int d = depth / ONE_PLY;
-        Value bonus = Value(d * d + 2 * d - 2);
-        Square prevSq = to_sq((ss-1)->currentMove);
-        update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus);
-    }
+        update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus(depth));
 
     tte->save(posKey, value_to_tt(bestValue, ss->ply),
               bestValue >= beta ? BOUND_LOWER :