Singular quiet LMR

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index a3d4a329a1f7c4075f68e7e5261104d679cbbffc..1e133447d381b547f97d9ea93ab7aa7321d862f7 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -61,8 +61,8 @@ namespace {
   // Different node types, used as a template parameter
   enum NodeType { NonPV, PV };
 
-  constexpr uint64_t ttHitAverageWindow     = 4096;
-  constexpr uint64_t ttHitAverageResolution = 1024;
+  constexpr uint64_t TtHitAverageWindow     = 4096;
+  constexpr uint64_t TtHitAverageResolution = 1024;
 
   // Razor and futility margins
   constexpr int RazorMargin = 531;
@@ -272,9 +272,9 @@ void MainThread::search() {
   Thread* bestThread = this;
 
   // Check if there are threads with a better score than main thread
-  if (    Options["MultiPV"] == 1
+  if (    int(Options["MultiPV"]) == 1
       && !Limits.depth
-      && !(Skill(Options["Skill Level"]).enabled() || Options["UCI_LimitStrength"])
+      && !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"]))
       &&  rootMoves[0].pv[0] != MOVE_NONE)
   {
       std::map<Move, int64_t> votes;
@@ -350,14 +350,17 @@ void Thread::search() {
   if (mainThread)
   {
       if (mainThread->bestPreviousScore == VALUE_INFINITE)
-          for (int i=0; i<4; ++i)
+          for (int i = 0; i < 4; ++i)
               mainThread->iterValue[i] = VALUE_ZERO;
       else
-          for (int i=0; i<4; ++i)
+          for (int i = 0; i < 4; ++i)
               mainThread->iterValue[i] = mainThread->bestPreviousScore;
   }
 
-  size_t multiPV = Options["MultiPV"];
+  std::copy(&lowPlyHistory[2][0], &lowPlyHistory.back().back() + 1, &lowPlyHistory[0][0]);
+  std::fill(&lowPlyHistory[MAX_LPH - 2][0], &lowPlyHistory.back().back() + 1, 0);
+
+  size_t multiPV = size_t(Options["MultiPV"]);
 
   // Pick integer skill levels, but non-deterministically round up or down
   // such that the average integer skill corresponds to the input floating point one.
@@ -378,7 +381,7 @@ void Thread::search() {
       multiPV = std::max(multiPV, (size_t)4);
 
   multiPV = std::min(multiPV, rootMoves.size());
-  ttHitAverage = ttHitAverageWindow * ttHitAverageResolution / 2;
+  ttHitAverage = TtHitAverageWindow * TtHitAverageResolution / 2;
 
   int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns
 
@@ -537,8 +540,8 @@ void Thread::search() {
           && !Threads.stop
           && !mainThread->stopOnPonderhit)
       {
-          double fallingEval = (332 +  6 * (mainThread->bestPreviousScore - bestValue)
-                                    +  6 * (mainThread->iterValue[iterIdx]  - bestValue)) / 704.0;
+          double fallingEval = (332 + 6 * (mainThread->bestPreviousScore - bestValue)
+                                    + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 704.0;
           fallingEval = Utility::clamp(fallingEval, 0.5, 1.5);
 
           // If the bestMove is stable over several iterations, reduce time accordingly
@@ -627,7 +630,8 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval, maxValue;
     bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture;
-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularLMR;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
+         ttCapture, singularQuietLMR;
     Piece movedPiece;
     int moveCount, captureCount, quietCount;
 
@@ -702,8 +706,8 @@ namespace {
         thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5);
 
     // thisThread->ttHitAverage can be used to approximate the running average of ttHit
-    thisThread->ttHitAverage =   (ttHitAverageWindow - 1) * thisThread->ttHitAverage / ttHitAverageWindow
-                                + ttHitAverageResolution * ttHit;
+    thisThread->ttHitAverage =   (TtHitAverageWindow - 1) * thisThread->ttHitAverage / TtHitAverageWindow
+                                + TtHitAverageResolution * ttHit;
 
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
@@ -968,7 +972,7 @@ moves_loop: // When in check, search starts from here
                                       depth > 12 ? ss->ply : MAX_PLY);
 
     value = bestValue;
-    singularLMR = moveCountPruning = false;
+    singularQuietLMR = moveCountPruning = false;
     ttCapture = ttMove && pos.capture_or_promotion(ttMove);
 
     // Mark this node as being searched
@@ -1049,6 +1053,14 @@ moves_loop: // When in check, search starts from here
                   && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
                   continue;
 
+              // Futility pruning for captures
+              if (   !givesCheck
+                  && lmrDepth < 6
+                  && !(PvNode && abs(bestValue) < 2)
+                  && !ss->inCheck
+                  && ss->staticEval + 270 + 384 * lmrDepth + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha)
+                  continue;
+
               // See based pruning
               if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo)
                   continue;
@@ -1081,7 +1093,7 @@ moves_loop: // When in check, search starts from here
           if (value < singularBeta)
           {
               extension = 1;
-              singularLMR = true;
+              singularQuietLMR = !ttCapture;
           }
 
           // Multi-cut pruning
@@ -1163,12 +1175,12 @@ moves_loop: // When in check, search starts from here
               || moveCountPruning
               || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
               || cutNode
-              || thisThread->ttHitAverage < 375 * ttHitAverageResolution * ttHitAverageWindow / 1024))
+              || thisThread->ttHitAverage < 375 * TtHitAverageResolution * TtHitAverageWindow / 1024))
       {
           Depth r = reduction(improving, depth, moveCount);
 
           // Decrease reduction if the ttHit running average is large
-          if (thisThread->ttHitAverage > 500 * ttHitAverageResolution * ttHitAverageWindow / 1024)
+          if (thisThread->ttHitAverage > 500 * TtHitAverageResolution * TtHitAverageWindow / 1024)
               r--;
 
           // Reduction if other threads are searching this position.
@@ -1187,7 +1199,7 @@ moves_loop: // When in check, search starts from here
               r--;
 
           // Decrease reduction if ttMove has been singularly extended (~3 Elo)
-          if (singularLMR)
+          if (singularQuietLMR)
               r -= 1 + formerPv;
 
           if (!captureOrPromotion)