X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=a26a9ab8cbc1092d8a34171cc7a5765a2aaf0c48;hp=62788faac38f0002c2f416cfec421b83d3b76504;hb=883367d21749eb91a5a3737338b5a7f507751a5a;hpb=7b6fa353a3858b092e1a43ef69b3035cb5d3b5c0

diff --git a/src/search.cpp b/src/search.cpp
index 62788faa..a26a9ab8 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -448,7 +448,7 @@ void Thread::search() {
               {
                   beta = std::min(bestValue + delta, VALUE_INFINITE);
                   if (mainThread)
-                	  ++failedHighCnt;
+                      ++failedHighCnt;
               }
               else
                   break;
@@ -492,10 +492,8 @@ void Thread::search() {
           && !Threads.stop
           && !Threads.stopOnPonderhit)
           {
-              const int F[] = { failedLow,
-                                bestValue - mainThread->previousScore };
-
-              int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1]));
+              double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0;
+              fallingEval        = std::max(0.5, std::min(1.5, fallingEval));
 
               // If the bestMove is stable over several iterations, reduce time accordingly
               timeReduction = 1.0;
@@ -509,7 +507,7 @@ void Thread::search() {
 
               // Stop the search if we have only one legal move, or if available time elapsed
               if (   rootMoves.size() == 1
-                  || Time.elapsed() > Time.optimum() * bestMoveInstability * improvingFactor / 581)
+                  || Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval)
               {
                   // If we are allowed to ponder do not stop the search now but
                   // keep pondering until the GUI sends "ponderhit" or "stop".
@@ -828,8 +826,8 @@ namespace {
         &&  depth >= 5 * ONE_PLY
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY)
     {
-        Value rbeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
-        MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory);
+        Value raisedBeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
+        MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory);
         int probCutCount = 0;
 
         while (  (move = mp.next_move()) != MOVE_NONE
@@ -846,15 +844,15 @@ namespace {
                 pos.do_move(move, st);
 
                 // Perform a preliminary qsearch to verify that the move holds
-                value = -qsearch<NonPV>(pos, ss+1, -rbeta, -rbeta+1);
+                value = -qsearch<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1);
 
                 // If the qsearch held perform the regular search
-                if (value >= rbeta)
-                    value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode);
+                if (value >= raisedBeta)
+                    value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4 * ONE_PLY, !cutNode);
 
                 pos.undo_move(move);
 
-                if (value >= rbeta)
+                if (value >= raisedBeta)
                     return value;
             }
     }
@@ -930,18 +928,18 @@ moves_loop: // When in check, search starts from here
       if (    depth >= 8 * ONE_PLY
           &&  move == ttMove
           && !rootNode
-          && !excludedMove // Recursive singular search is not allowed
+          && !excludedMove // Avoid recursive singular search
           &&  ttValue != VALUE_NONE
           && (tte->bound() & BOUND_LOWER)
           &&  tte->depth() >= depth - 3 * ONE_PLY
           &&  pos.legal(move))
       {
-          Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
+          Value reducedBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
           ss->excludedMove = move;
-          value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+          value = search<NonPV>(pos, ss, reducedBeta - 1, reducedBeta, depth / 2, cutNode);
           ss->excludedMove = MOVE_NONE;
 
-          if (value < rBeta)
+          if (value < reducedBeta)
               extension = ONE_PLY;
       }
       else if (    givesCheck // Check extension (~2 Elo)
@@ -975,7 +973,7 @@ moves_loop: // When in check, search starts from here
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
 
               // Countermoves based pruning (~20 Elo)
-              if (   lmrDepth < 3 + ((ss-1)->statScore > 0)
+              if (   lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
                   && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
                   && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
                   continue;
@@ -1187,9 +1185,12 @@ moves_loop: // When in check, search starts from here
 
         update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));
 
-        // Extra penalty for a quiet TT move in previous ply when it gets refuted
-        if ((ss-1)->moveCount == 1 && !pos.captured_piece())
-            update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
+        // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted
+        if (   (ss-1)->moveCount == 1
+            || ((ss-1)->currentMove == (ss-1)->killers[0] && (ss-1)->killers[0]))
+            if (!pos.captured_piece())
+                update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
+
     }
     // Bonus for prior countermove that caused the fail low
     else if (   (depth >= 3 * ONE_PLY || PvNode)