Clean up repetitive declarations for see_ge

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 17c1c28b2646eadd6ec565892f7f0a39620a92a4..ac74cdaf885e5574b0ccf8c2030934e4cad14f48 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -607,14 +607,7 @@ namespace {
     (ss+2)->cutoffCnt    = 0;
     ss->doubleExtensions = (ss-1)->doubleExtensions;
     Square prevSq        = is_ok((ss-1)->currentMove) ? to_sq((ss-1)->currentMove) : SQ_NONE;
-
-    // Initialize statScore to zero for the grandchildren of the current position.
-    // So statScore is shared between all grandchildren and only the first grandchild
-    // starts with statScore = 0. Later grandchildren start with the last calculated
-    // statScore of the previous grandchild. This influences the reduction rules in
-    // LMR which are based on the statScore of parent position.
-    if (!rootNode)
-        (ss+2)->statScore = 0;
+    ss->statScore        = 0;
 
     // Step 4. Transposition table lookup.
     excludedMove = ss->excludedMove;
@@ -732,7 +725,7 @@ namespace {
     }
     else if (excludedMove)
     {
-        // Providing the hint that this node's accumulator will be used often brings significant Elo gain (13 elo)
+        // Providing the hint that this node's accumulator will be used often brings significant Elo gain (13 Elo)
         Eval::NNUE::hint_common_parent_position(pos);
         eval = ss->staticEval;
         complexity = abs(ss->staticEval - pos.psq_eg_stm());
@@ -1019,9 +1012,27 @@ moves_loop: // When in check, search starts here
                    + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha)
                   continue;
 
+              Bitboard occupied;
               // SEE based pruning (~11 Elo)
-              if (!pos.see_ge(move, Value(-206) * depth))
-                  continue;
+              if (!pos.see_ge(move, occupied, Value(-206) * depth))
+              {
+                  if (depth < 2 - capture)
+                      continue;
+                  // don't prune move if a heavy enemy piece (KQR) is under attack after the exchanges
+                  Bitboard leftEnemies = (pos.pieces(~us, QUEEN, ROOK) | pos.pieces(~us, KING)) & occupied;
+                  Bitboard attacks = 0;
+                  occupied |= to_sq(move);
+                  while (leftEnemies && !attacks)
+                  {
+                      Square sq = pop_lsb(leftEnemies);
+                      attacks |= pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
+                      // exclude Queen/Rook(s) which were already threatened before SEE
+                      if (attacks && (sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us))))
+                          attacks = 0;
+                  }
+                  if (!attacks)
+                      continue;
+              }
           }
           else
           {
@@ -1101,15 +1112,15 @@ moves_loop: // When in check, search starts here
               else if (singularBeta >= beta)
                   return singularBeta;
 
-              // If the eval of ttMove is greater than beta, we reduce it (negative extension)
+              // If the eval of ttMove is greater than beta, we reduce it (negative extension) (~7 Elo)
               else if (ttValue >= beta)
                   extension = -2 - !PvNode;
 
-              // If the eval of ttMove is less than value, we reduce it (negative extension)
+              // If the eval of ttMove is less than value, we reduce it (negative extension) (~1 Elo)
               else if (ttValue <= value)
                   extension = -1;
 
-              // If the eval of ttMove is less than alpha, we reduce it (negative extension)
+              // If the eval of ttMove is less than alpha, we reduce it (negative extension) (~1 Elo)
               else if (ttValue <= alpha)
                   extension = -1;
           }
@@ -1163,7 +1174,7 @@ moves_loop: // When in check, search starts here
       if (ttCapture)
           r++;
 
-      // Decrease reduction for PvNodes based on depth
+      // Decrease reduction for PvNodes based on depth (~2 Elo)
       if (PvNode)
           r -= 1 + 12 / (3 + depth);
 
@@ -1176,11 +1187,11 @@ moves_loop: // When in check, search starts here
           && (mp.threatenedPieces & from_sq(move)))
           r--;
 
-      // Increase reduction if next ply has a lot of fail high
+      // Increase reduction if next ply has a lot of fail high (~5 Elo)
       if ((ss+1)->cutoffCnt > 3)
           r++;
 
-      // Decrease reduction if move is a killer and we have a good history
+      // Decrease reduction if move is a killer and we have a good history (~1 Elo)
       if (move == ss->killers[0]
           && (*contHist[0])[movedPiece][to_sq(move)] >= 3722)
           r--;
@@ -1191,7 +1202,7 @@ moves_loop: // When in check, search starts here
                      + (*contHist[3])[movedPiece][to_sq(move)]
                      - 4182;
 
-      // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
+      // Decrease/increase reduction for moves with a good/bad history (~25 Elo)
       r -= ss->statScore / (11791 + 3992 * (depth > 6 && depth < 19));
 
       // Step 17. Late moves reduction / extension (LMR, ~117 Elo)
@@ -1328,7 +1339,7 @@ moves_loop: // When in check, search starts here
               {
                   alpha = value;
 
-                  // Reduce other moves if we have found at least one score improvement
+                  // Reduce other moves if we have found at least one score improvement (~1 Elo)
                   if (   depth > 1
                       && depth < 6
                       && beta  <  10534
@@ -1394,7 +1405,7 @@ moves_loop: // When in check, search starts here
         bestValue = std::min(bestValue, maxValue);
 
     // If no good move is found and the previous position was ttPv, then the previous
-    // opponent move is probably good and the new position is added to the search tree.
+    // opponent move is probably good and the new position is added to the search tree. (~7 Elo)
     if (bestValue <= alpha)
         ss->ttPv = ss->ttPv || ((ss-1)->ttPv && depth > 3);
 
@@ -1413,7 +1424,7 @@ moves_loop: // When in check, search starts here
 
   // qsearch() is the quiescence search function, which is called by the main search
   // function with zero depth, or recursively with further decreasing depth per call.
-  // (~155 elo)
+  // (~155 Elo)
   template <NodeType nodeType>
   Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {