Small cleanups

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cfb569b90934e6cab2fc1cc7bec602aa5035d8ff..d6571a140f36b1e9ab5293895aff192df271a785 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -601,7 +601,6 @@ namespace {
 
     assert(0 <= ss->ply && ss->ply < MAX_PLY);
 
-    (ss+1)->ttPv         = false;
     (ss+1)->excludedMove = bestMove = MOVE_NONE;
     (ss+2)->killers[0]   = (ss+2)->killers[1] = MOVE_NONE;
     (ss+2)->cutoffCnt    = 0;
@@ -623,7 +622,7 @@ namespace {
     ttValue = ss->ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
     ttMove =  rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
             : ss->ttHit    ? tte->move() : MOVE_NONE;
-    ttCapture = ttMove && pos.capture(ttMove);
+    ttCapture = ttMove && pos.capture_stage(ttMove);
 
     // At this point, if excluded, skip straight to step 6, static eval. However,
     // to save indentation, we list the condition in all code between here and there.
@@ -852,7 +851,7 @@ namespace {
     probCutBeta = beta + 186 - 54 * improving;
 
     // Step 10. ProbCut (~10 Elo)
-    // If we have a good enough capture and a reduced search returns a value
+    // If we have a good enough capture (or queen promotion) and a reduced search returns a value
     // much above beta, we can (almost) safely prune the previous move.
     if (   !PvNode
         &&  depth > 4
@@ -873,7 +872,7 @@ namespace {
         while ((move = mp.next_move()) != MOVE_NONE)
             if (move != excludedMove && pos.legal(move))
             {
-                assert(pos.capture(move) || promotion_type(move) == QUEEN);
+                assert(pos.capture_stage(move));
 
                 ss->currentMove = move;
                 ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
@@ -985,7 +984,7 @@ moves_loop: // When in check, search starts here
           (ss+1)->pv = nullptr;
 
       extension = 0;
-      capture = pos.capture(move);
+      capture = pos.capture_stage(move);
       movedPiece = pos.moved_piece(move);
       givesCheck = pos.gives_check(move);
 
@@ -1071,11 +1070,10 @@ moves_loop: // When in check, search starts here
               && (tte->bound() & BOUND_LOWER)
               &&  tte->depth() >= depth - 3)
           {
-              Value singularBeta = ttValue - (2 + (ss->ttPv && !PvNode)) * depth;
+              Value singularBeta = ttValue - (3 + 2 * (ss->ttPv && !PvNode)) * depth / 2;
               Depth singularDepth = (depth - 1) / 2;
 
               ss->excludedMove = move;
-              // the search with excludedMove will update ss->staticEval
               value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
               ss->excludedMove = MOVE_NONE;
 
@@ -1104,11 +1102,15 @@ moves_loop: // When in check, search starts here
 
               // If the eval of ttMove is greater than beta, we reduce it (negative extension)
               else if (ttValue >= beta)
-                  extension = -2;
+                  extension = -2 - !PvNode;
 
               // If the eval of ttMove is less than value, we reduce it (negative extension)
               else if (ttValue <= value)
                   extension = -1;
+
+              // If the eval of ttMove is less than alpha, we reduce it (negative extension)
+              else if (ttValue <= alpha)
+                  extension = -1;
           }
 
           // Check extensions (~1 Elo)
@@ -1383,8 +1385,7 @@ moves_loop: // When in check, search starts here
     // Bonus for prior countermove that caused the fail low
     else if (!priorCapture)
     {
-        // Extra bonuses for PV/Cut nodes or bad fail lows
-        int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 97 * depth);
+        int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 97 * depth) + ((ss-1)->moveCount > 10);
         update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
     }
 
@@ -1543,7 +1544,7 @@ moves_loop: // When in check, search starts here
           continue;
 
       givesCheck = pos.gives_check(move);
-      capture = pos.capture(move);
+      capture = pos.capture_stage(move);
 
       moveCount++;
 
@@ -1716,7 +1717,7 @@ moves_loop: // When in check, search starts here
     PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
     int bonus1 = stat_bonus(depth + 1);
 
-    if (!pos.capture(bestMove))
+    if (!pos.capture_stage(bestMove))
     {
         int bonus2 = bestValue > beta + 153 ? bonus1               // larger bonus
                                             : stat_bonus(depth);   // smaller bonus