Introduce recapture extensions

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index a8f178a31ca317620ac4aded289651c92d17648f..5c53c0dae8bf6a14dade4b2ee3fe5b55f21eff0b 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -372,8 +372,8 @@ void Thread::search() {
             beta      = std::min(avg + delta, VALUE_INFINITE);
 
             // Adjust optimism based on root move's averageScore (~4 Elo)
-            optimism[us]  = 103 * (avg + 33) / (std::abs(avg + 34) + 119);
-            optimism[~us] = -116 * (avg + 40) / (std::abs(avg + 12) + 123);
+            optimism[us]  = 103 * avg / (std::abs(avg) + 119);
+            optimism[~us] = -116 * avg / (std::abs(avg) + 123);
 
             // Start with a small aspiration window and, in the case of a fail
             // high/low, re-search with a bigger window until we don't fail
@@ -855,8 +855,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
     {
         assert(probCutBeta < VALUE_INFINITE);
 
-        MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory,
-                      thisThread->pawnHistory);
+        MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory);
 
         while ((move = mp.next_move()) != MOVE_NONE)
             if (move != excludedMove && pos.legal(move))
@@ -915,7 +914,7 @@ moves_loop:  // When in check, search starts here
       prevSq != SQ_NONE ? thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] : MOVE_NONE;
 
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &captureHistory, contHist,
-                  thisThread->pawnHistory, countermove, ss->killers);
+                  &thisThread->pawnHistory, countermove, ss->killers);
 
     value            = bestValue;
     moveCountPruning = singularQuietLMR = false;
@@ -1101,6 +1100,12 @@ moves_loop:  // When in check, search starts here
             else if (PvNode && move == ttMove && move == ss->killers[0]
                      && (*contHist[0])[movedPiece][to_sq(move)] >= 4194)
                 extension = 1;
+
+            // Recapture extensions (~1 Elo)
+            else if (PvNode && move == ttMove && to_sq(move) == prevSq
+                     && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))]
+                          > 4000)
+                extension = 1;
         }
 
         // Add extension to new depth
@@ -1484,7 +1489,7 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
     // will be generated.
     Square     prevSq = is_ok((ss - 1)->currentMove) ? to_sq((ss - 1)->currentMove) : SQ_NONE;
     MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory,
-                  contHist, thisThread->pawnHistory, prevSq);
+                  contHist, &thisThread->pawnHistory, prevSq);
 
     int quietCheckEvasions = 0;