Cleanup code

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 004d061b7b6929afee75d82ab6fb1face7a54190..565fba0f89f7ece8ffccaf1aef5ea00beff5b3b6 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -81,7 +81,7 @@ namespace {
 
   // History and stats update bonus, based on depth
   int stat_bonus(Depth d) {
-    return std::min((9 * d + 270) * d - 311 , 2145);
+    return std::min((8 * d + 240) * d - 276 , 1907);
   }
 
   // Add a small random component to draw evaluations to avoid 3-fold blindness
@@ -558,14 +558,13 @@ namespace {
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
-    bool givesCheck, improving, didLMR, priorCapture;
+    bool givesCheck, improving, didLMR, priorCapture, singularQuietLMR;
     bool capture, doFullDepthSearch, moveCountPruning, ttCapture;
     Piece movedPiece;
     int moveCount, captureCount, quietCount, improvement, complexity;
 
     // Step 1. Initialize node
     Thread* thisThread = pos.this_thread();
-    thisThread->depth  = depth;
     ss->inCheck        = pos.checkers();
     priorCapture       = pos.captured_piece();
     Color us           = pos.side_to_move();
@@ -945,7 +944,7 @@ moves_loop: // When in check, search starts here
                                       ss->killers);
 
     value = bestValue;
-    moveCountPruning = false;
+    moveCountPruning = singularQuietLMR = 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.
@@ -1033,7 +1032,7 @@ moves_loop: // When in check, search starts here
                   && history < -3875 * (depth - 1))
                   continue;
 
-              history += thisThread->mainHistory[us][from_to(move)];
+              history += 2 * thisThread->mainHistory[us][from_to(move)];
 
               // Futility pruning: parent node (~9 Elo)
               if (   !ss->inCheck
@@ -1075,6 +1074,7 @@ 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
@@ -1167,11 +1167,15 @@ moves_loop: // When in check, search starts here
           if (PvNode)
               r -= 1 + 15 / (3 + depth);
 
+          // Decrease reduction if ttMove has been singularly extended (~1 Elo)
+          if (singularQuietLMR)
+              r--;
+
           // Increase reduction if next ply has a lot of fail high else reset count to 0
           if ((ss+1)->cutoffCnt > 3 && !PvNode)
               r++;
 
-          ss->statScore =  thisThread->mainHistory[us][from_to(move)]
+          ss->statScore =  2 * thisThread->mainHistory[us][from_to(move)]
                          + (*contHist[0])[movedPiece][to_sq(move)]
                          + (*contHist[1])[movedPiece][to_sq(move)]
                          + (*contHist[3])[movedPiece][to_sq(move)]