Remove lowPly history

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cded8614ad9d6c77851b5b71db034ec96baa0e38..2abfbaf2f3dd35d6f0fb414a03fa13b327bcca90 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -141,7 +141,7 @@ namespace {
   Value value_from_tt(Value v, int ply, int r50c);
   void update_pv(Move* pv, Move move, Move* childPv);
   void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus);
-  void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth);
+  void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus);
   void update_all_stats(const Position& pos, Stack* ss, Move bestMove, Value bestValue, Value beta, Square prevSq,
                         Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth);
 
@@ -317,9 +317,6 @@ void Thread::search() {
               mainThread->iterValue[i] = mainThread->bestPreviousScore;
   }
 
-  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"]);
   Skill skill(Options["Skill Level"], Options["UCI_LimitStrength"] ? int(Options["UCI_Elo"]) : 0);
 
@@ -490,9 +487,8 @@ void Thread::search() {
           && !Threads.stop
           && !mainThread->stopOnPonderhit)
       {
-          double fallingEval = (142 + 6 * (mainThread->bestPreviousScore - bestValue)
-                                    + 6 * (mainThread->bestPreviousAverageScore - bestValue)
-                                    + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 825.0;
+          double fallingEval = (142 + 12 * (mainThread->bestPreviousAverageScore - bestValue)
+                                    +  6 * (mainThread->iterValue[iterIdx] - bestValue)) / 825.0;
           fallingEval = std::clamp(fallingEval, 0.5, 1.5);
 
           // If the bestMove is stable over several iterations, reduce time accordingly
@@ -591,8 +587,7 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
     bool givesCheck, improving, didLMR, priorCapture;
-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
-         ttCapture, singularQuietLMR;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
     Piece movedPiece;
     int moveCount, captureCount, quietCount, bestMoveCount, improvement;
 
@@ -668,14 +663,6 @@ namespace {
     if (!excludedMove)
         ss->ttPv = PvNode || (ss->ttHit && tte->is_pv());
 
-    // Update low ply history for previous move if we are near root and position is or has been in PV
-    if (   ss->ttPv
-        && depth > 12
-        && ss->ply - 1 < MAX_LPH
-        && !priorCapture
-        && is_ok((ss-1)->currentMove))
-        thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5);
-
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
         && ss->ttHit
@@ -691,7 +678,7 @@ namespace {
             {
                 // Bonus for a quiet ttMove that fails high
                 if (!ttCapture)
-                    update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth);
+                    update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));
 
                 // Extra penalty for early quiet moves of the previous ply
                 if ((ss-1)->moveCount <= 2 && !priorCapture)
@@ -975,15 +962,13 @@ moves_loop: // When in check, search starts here
     Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
 
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
-                                      &thisThread->lowPlyHistory,
                                       &captureHistory,
                                       contHist,
                                       countermove,
-                                      ss->killers,
-                                      ss->ply);
+                                      ss->killers);
 
     value = bestValue;
-    singularQuietLMR = moveCountPruning = false;
+    moveCountPruning = false;
 
     // Indicate PvNodes that will probably fail low if the node was searched
     // at a depth equal or greater than the current depth, and the result of this search was a fail low.
@@ -1107,7 +1092,6 @@ moves_loop: // When in check, search starts here
           if (value < singularBeta)
           {
               extension = 1;
-              singularQuietLMR = !ttCapture;
 
               // Avoid search explosion by limiting the number of double extensions
               if (   !PvNode
@@ -1191,7 +1175,7 @@ moves_loop: // When in check, search starts here
               && !likelyFailLow)
               r -= 2;
 
-          // Increase reduction at non-PV nodes
+          // Increase reduction at non-PV nodes (~3 Elo)
           if (!PvNode)
               r++;
 
@@ -1199,10 +1183,6 @@ moves_loop: // When in check, search starts here
           if ((ss-1)->moveCount > 13)
               r--;
 
-          // Decrease reduction if ttMove has been singularly extended (~1 Elo)
-          if (singularQuietLMR)
-              r--;
-
           // Increase reduction for cut nodes (~3 Elo)
           if (cutNode && move != ss->killers[0])
               r += 2;
@@ -1715,7 +1695,7 @@ moves_loop: // When in check, search starts here
     if (!pos.capture_or_promotion(bestMove))
     {
         // Increase stats for the best move in case it was a quiet move
-        update_quiet_stats(pos, ss, bestMove, bonus2, depth);
+        update_quiet_stats(pos, ss, bestMove, bonus2);
 
         // Decrease stats for all non-best quiet moves
         for (int i = 0; i < quietCount; ++i)
@@ -1762,7 +1742,7 @@ moves_loop: // When in check, search starts here
 
   // update_quiet_stats() updates move sorting heuristics
 
-  void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth) {
+  void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus) {
 
     // Update killers
     if (ss->killers[0] != move)
@@ -1782,10 +1762,6 @@ moves_loop: // When in check, search starts here
         Square prevSq = to_sq((ss-1)->currentMove);
         thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move;
     }
-
-    // Update low ply history
-    if (depth > 11 && ss->ply < MAX_LPH)
-        thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7);
   }
 
   // When playing with strength handicap, choose best move among a set of RootMoves