Remove recaptures stage in qsearch

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index ae83ab3475831d91b07668c94599c89404b4ef3e..160031384838abdc9ba8b5c882dc754a04bb5cd0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -94,10 +94,10 @@ constexpr int futility_move_count(bool improving, Depth depth) {
 }
 
 // History and stats update bonus, based on depth
-int stat_bonus(Depth d) { return std::min(364 * d - 438, 1501); }
+int stat_bonus(Depth d) { return std::min(291 * d - 350, 1200); }
 
 // History and stats update malus, based on depth
-int stat_malus(Depth d) { return std::min(452 * d - 452, 1478); }
+int stat_malus(Depth d) { return std::min(361 * d - 361, 1182); }
 
 // Add a small random component to draw evaluations to avoid 3-fold blindness
 Value value_draw(const Thread* thisThread) {
@@ -746,7 +746,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
     // Use static evaluation difference to improve quiet move ordering (~4 Elo)
     if (is_ok((ss - 1)->currentMove) && !(ss - 1)->inCheck && !priorCapture)
     {
-        int bonus = std::clamp(-18 * int((ss - 1)->staticEval + ss->staticEval), -1812, 1812);
+        int bonus = std::clamp(-14 * int((ss - 1)->staticEval + ss->staticEval), -1449, 1449);
         thisThread->mainHistory[~us][from_to((ss - 1)->currentMove)] << bonus;
         if (type_of(pos.piece_on(prevSq)) != PAWN && type_of((ss - 1)->currentMove) != PROMOTION)
             thisThread->pawnHistory[pawn_structure(pos)][pos.piece_on(prevSq)][prevSq] << bonus / 4;
@@ -834,8 +834,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
     if (depth <= 0)
         return qsearch<PV>(pos, ss, alpha, beta);
 
-    // For cutNodes without a ttMove, we decrease depth by 2
-    // if current depth >= 8.
+    // For cutNodes without a ttMove, we decrease depth by 2 if depth is high enough.
     if (cutNode && depth >= 8 && !ttMove)
         depth -= 2;
 
@@ -1037,7 +1036,7 @@ moves_loop:  // When in check, search starts here
 
             // Note: the depth margin and singularBeta margin are known for having non-linear
             // scaling. Their values are optimized to time controls of 180+1.8 and longer
-            // so changing them requires tests at this type of time controls.
+            // so changing them requires tests at these types of time controls.
             // Recursive singular search is avoided.
             if (!rootNode && move == ttMove && !excludedMove
                 && depth >= 4 - (thisThread->completedDepth > 24) + 2 * (PvNode && tte->is_pv())
@@ -1079,7 +1078,7 @@ moves_loop:  // When in check, search starts here
                 // we do not know if the ttMove is singular or can do a multi-cut,
                 // so we reduce the ttMove in favor of other moves based on some conditions:
 
-                // If the ttMove is assumed to fail high over currnet beta (~7 Elo)
+                // If the ttMove is assumed to fail high over current beta (~7 Elo)
                 else if (ttValue >= beta)
                     extension = -2 - !PvNode;
 
@@ -1155,7 +1154,7 @@ moves_loop:  // When in check, search starts here
         if ((ss + 1)->cutoffCnt > 3)
             r++;
 
-        // Set reduction to 0 for first generated move (ttMove)
+        // Set reduction to 0 for first picked move (ttMove) (~2 Elo)
         // Nullifies all previous reduction adjustments to ttMove and leaves only history to do them
         else if (move == ttMove)
             r = 0;
@@ -1166,13 +1165,13 @@ moves_loop:  // When in check, search starts here
                       + (*contHist[3])[movedPiece][to_sq(move)] - 3848;
 
         // Decrease/increase reduction for moves with a good/bad history (~25 Elo)
-        r -= ss->statScore / (10216 + 3855 * (depth > 5 && depth < 23));
+        r -= ss->statScore / 14200;
 
         // Step 17. Late moves reduction / extension (LMR, ~117 Elo)
         // We use various heuristics for the sons of a node after the first son has
         // been searched. In general, we would like to reduce them, but there are many
         // cases where we extend a son if it has good chances to be "interesting".
-        if (depth >= 2 && moveCount > 1 + (PvNode && ss->ply <= 1)
+        if (depth >= 2 && moveCount > 1 + rootNode
             && (!ss->ttPv || !capture || (cutNode && (ss - 1)->moveCount > 1)))
         {
             // In general we want to cap the LMR depth search at newDepth, but when
@@ -1189,8 +1188,8 @@ moves_loop:  // When in check, search starts here
             {
                 // Adjust full-depth search based on LMR results - if the result
                 // was good enough search deeper, if it was bad enough search shallower.
-                const bool doDeeperSearch     = value > (bestValue + 51 + 10 * (newDepth - d));
-                const bool doShallowerSearch  = value < bestValue + newDepth;
+                const bool doDeeperSearch    = value > (bestValue + 50 + 2 * newDepth);  // (~1 Elo)
+                const bool doShallowerSearch = value < bestValue + newDepth;             // (~2 Elo)
 
                 newDepth += doDeeperSearch - doShallowerSearch;
 
@@ -1459,7 +1458,7 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
                 bestValue = ttValue;
         }
         else
-            // In case of null move search use previous static eval with a different sign
+            // In case of null move search, use previous static eval with a different sign
             ss->staticEval = bestValue =
               (ss - 1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss - 1)->staticEval;
 
@@ -1488,7 +1487,7 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
     // will be generated.
     Square     prevSq = is_ok((ss - 1)->currentMove) ? to_sq((ss - 1)->currentMove) : SQ_NONE;
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory,
-                  contHist, &thisThread->pawnHistory, prevSq);
+                  contHist, &thisThread->pawnHistory);
 
     int quietCheckEvasions = 0;
 
@@ -1688,7 +1687,7 @@ void update_all_stats(const Position& pos,
     PieceType              captured;
 
     int quietMoveBonus = stat_bonus(depth + 1);
-    int quietMoveMalus = stat_malus(depth + 1);
+    int quietMoveMalus = stat_malus(depth);
 
     if (!pos.capture_stage(bestMove))
     {
@@ -1899,9 +1898,9 @@ string UCI::pv(const Position& pos, Depth depth) {
 }
 
 
-// Called in case we have no ponder move
-// before exiting the search, for instance, in case we stop the search during a
-// fail high at root. We try hard to have a ponder move to return to the GUI,
+// Called in case we have no ponder move before exiting the search,
+// for instance, in case we stop the search during a fail high at root.
+// We try hard to have a ponder move to return to the GUI,
 // otherwise in case of 'ponder on' we have nothing to think about.
 bool RootMove::extract_ponder_from_tt(Position& pos) {