Simplify away late irreversible move extension

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cdbccb4c0abbc395f27465a33e6675ba133817d6..b96efad09aa615af0dd6fda0db756dcaef402905 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -82,7 +82,7 @@ namespace {
 
   // History and stats update bonus, based on depth
   int stat_bonus(Depth d) {
-    return d > 13 ? 29 : 17 * d * d + 134 * d - 134;
+    return d > 14 ? 29 : 8 * d * d + 224 * d - 215;
   }
 
   // Add a small random component to draw evaluations to avoid 3fold-blindness
@@ -815,9 +815,10 @@ namespace {
         tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
     }
 
-    if ((ss-1)->moveCount > 1 && is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture && depth < 7)
+    // Use static evaluation difference to improve quiet move ordering
+    if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
     {
-        int bonus = std::clamp(- (depth+1) * 2 * int((ss-1)->staticEval + ss->staticEval - 2 * Tempo), -1000, 1000);
+        int bonus = std::clamp(-depth * 4 * int((ss-1)->staticEval + ss->staticEval - 2 * Tempo), -1000, 1000);
         thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
     }
 
@@ -837,7 +838,7 @@ namespace {
 
     // Step 8. Futility pruning: child node (~50 Elo)
     if (   !PvNode
-        &&  depth < 8
+        &&  depth < 9
         &&  eval - futility_margin(depth, improving) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
         return eval;
@@ -892,7 +893,7 @@ namespace {
         }
     }
 
-    probCutBeta = beta + 183 - 49 * improving;
+    probCutBeta = beta + 194 - 49 * improving;
 
     // Step 10. ProbCut (~10 Elo)
     // If we have a good enough capture and a reduced search returns a value
@@ -1057,11 +1058,11 @@ moves_loop: // When in check, search starts from here
               // Futility pruning: parent node (~5 Elo)
               if (   lmrDepth < 7
                   && !ss->inCheck
-                  && ss->staticEval + 266 + 170 * lmrDepth <= alpha
+                  && ss->staticEval + 254 + 159 * lmrDepth <= alpha
                   &&  (*contHist[0])[movedPiece][to_sq(move)]
                     + (*contHist[1])[movedPiece][to_sq(move)]
                     + (*contHist[3])[movedPiece][to_sq(move)]
-                    + (*contHist[5])[movedPiece][to_sq(move)] / 2 < 27376)
+                    + (*contHist[5])[movedPiece][to_sq(move)] / 2 < 26394)
                   continue;
 
               // Prune moves with negative SEE (~20 Elo)
@@ -1077,7 +1078,7 @@ moves_loop: // When in check, search starts from here
                   continue;
 
               // SEE based pruning
-              if (!pos.see_ge(move, Value(-213) * depth)) // (~25 Elo)
+              if (!pos.see_ge(move, Value(-218) * depth)) // (~25 Elo)
                   continue;
           }
       }
@@ -1141,12 +1142,6 @@ moves_loop: // When in check, search starts from here
                && pos.non_pawn_material() <= 2 * RookValueMg)
           extension = 1;
 
-      // Late irreversible move extension
-      if (   move == ttMove
-          && pos.rule50_count() > 80
-          && (captureOrPromotion || type_of(movedPiece) == PAWN))
-          extension = 2;
-
       // Add extension to new depth
       newDepth += extension;
 
@@ -1171,6 +1166,7 @@ moves_loop: // When in check, search starts from here
               || moveCountPruning
               || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
               || cutNode
+              || (!PvNode && !formerPv && thisThread->captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 4506)
               || thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024))
       {
           Depth r = reduction(improving, depth, moveCount);