+ // Decrease reduction if position is or has been on the PV
+ // and node is not likely to fail low. (~3 Elo)
+ if ( ss->ttPv
+ && !likelyFailLow)
+ r -= 2;
+
+ // Increase reduction at root and non-PV nodes when the best move does not change frequently
+ if ( (rootNode || !PvNode)
+ && thisThread->bestMoveChanges <= 2)
+ r++;
+
+ // Decrease reduction if opponent's move count is high (~1 Elo)
+ 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;
+
+ // Increase reduction if ttMove is a capture (~3 Elo)
+ if (ttCapture)
+ r++;
+
+ ss->statScore = thisThread->mainHistory[us][from_to(move)]
+ + (*contHist[0])[movedPiece][to_sq(move)]
+ + (*contHist[1])[movedPiece][to_sq(move)]
+ + (*contHist[3])[movedPiece][to_sq(move)]
+ - 4923;
+
+ // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
+ r -= ss->statScore / 14721;
+
+ // In general we want to cap the LMR depth search at newDepth. But if reductions
+ // are really negative and movecount is low, we allow this move to be searched
+ // deeper than the first move (this may lead to hidden double extensions if
+ // newDepth got its own extension before).
+ int deeper = r >= -1 ? 0
+ : noLMRExtension ? 0
+ : moveCount <= 5 ? 1
+ : (depth > 6 && PvNode) ? 1
+ : 0;
+
+ Depth d = std::clamp(newDepth - r, 1, newDepth + deeper);