Compute ttCapture earlier

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 48694cb2dedebcebaec8dd59491ade87c41d2daf..1aaf53d84d1b018374a7bc612d57e34e968c5d35 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -80,7 +80,7 @@ namespace {
 
   // History and stats update bonus, based on depth
   int stat_bonus(Depth d) {
-    return d > 14 ? 73 : 6 * d * d + 229 * d - 215;
+    return std::min((6 * d + 229) * d - 215 , 2000);
   }
 
   // Add a small random component to draw evaluations to avoid 3-fold blindness
@@ -173,7 +173,7 @@ namespace {
 void Search::init() {
 
   for (int i = 1; i < MAX_MOVES; ++i)
-      Reductions[i] = int(21.9 * std::log(i));
+      Reductions[i] = int((21.9 + std::log(Threads.size()) / 2) * std::log(i));
 }
 
 
@@ -332,7 +332,6 @@ void Thread::search() {
 
   multiPV = std::min(multiPV, rootMoves.size());
 
-  ttHitAverage.set(50, 100);                  // initialize the running average at 50%
   doubleExtensionAverage[WHITE].set(0, 100);  // initialize the running average at 0%
   doubleExtensionAverage[BLACK].set(0, 100);  // initialize the running average at 0%
 
@@ -591,13 +590,13 @@ namespace {
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
          ttCapture, singularQuietLMR, noLMRExtension;
     Piece movedPiece;
-    int moveCount, captureCount, quietCount;
+    int moveCount, captureCount, quietCount, bestMoveCount;
 
     // Step 1. Initialize node
     ss->inCheck        = pos.checkers();
     priorCapture       = pos.captured_piece();
     Color us           = pos.side_to_move();
-    moveCount          = captureCount = quietCount = ss->moveCount = 0;
+    moveCount          = bestMoveCount = captureCount = quietCount = ss->moveCount = 0;
     bestValue          = -VALUE_INFINITE;
     maxValue           = VALUE_INFINITE;
 
@@ -659,6 +658,7 @@ namespace {
     ttValue = ss->ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
     ttMove =  rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
             : ss->ttHit    ? tte->move() : MOVE_NONE;
+    ttCapture = ttMove && pos.capture_or_promotion(ttMove);
     if (!excludedMove)
         ss->ttPv = PvNode || (ss->ttHit && tte->is_pv());
 
@@ -670,9 +670,6 @@ namespace {
         && is_ok((ss-1)->currentMove))
         thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5);
 
-    // running average of ttHit
-    thisThread->ttHitAverage.update(ss->ttHit);
-
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
         && ss->ttHit
@@ -687,7 +684,7 @@ namespace {
             if (ttValue >= beta)
             {
                 // Bonus for a quiet ttMove that fails high
-                if (!pos.capture_or_promotion(ttMove))
+                if (!ttCapture)
                     update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth);
 
                 // Extra penalty for early quiet moves of the previous ply
@@ -695,7 +692,7 @@ namespace {
                     update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + 1));
             }
             // Penalty for a quiet ttMove that fails low
-            else if (!pos.capture_or_promotion(ttMove))
+            else if (!ttCapture)
             {
                 int penalty = -stat_bonus(depth);
                 thisThread->mainHistory[us][from_to(ttMove)] << penalty;
@@ -790,7 +787,6 @@ namespace {
     else
     {
         // In case of null move search use previous static eval with a different sign
-        // and addition of two tempos
         if ((ss-1)->currentMove != MOVE_NULL)
             ss->staticEval = eval = evaluate(pos);
         else
@@ -953,7 +949,6 @@ namespace {
 
 moves_loop: // When in check, search starts here
 
-    ttCapture = ttMove && pos.capture_or_promotion(ttMove);
     int rangeReduction = 0;
 
     // Step 11. A small Probcut idea, when we are in check
@@ -1124,18 +1119,9 @@ moves_loop: // When in check, search starts here
           else if (singularBeta >= beta)
               return singularBeta;
 
-          // If the eval of ttMove is greater than beta we try also if there is another
-          // move that pushes it over beta, if so the position also has probably multiple
-          // moves giving fail highs. We will then reduce the ttMove (negative extension).
+          // If the eval of ttMove is greater than beta, we reduce it (negative extension)
           else if (ttValue >= beta)
-          {
-              ss->excludedMove = move;
-              value = search<NonPV>(pos, ss, beta - 1, beta, (depth + 3) / 2, cutNode);
-              ss->excludedMove = MOVE_NONE;
-
-              if (value >= beta)
-                  extension = -2;
-          }
+              extension = -2;
       }
 
       // Capture extensions for PvNodes and cutNodes
@@ -1187,11 +1173,9 @@ moves_loop: // When in check, search starts here
       {
           Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
 
-          if (PvNode)
-              r--;
-
-          // Decrease reduction if the ttHit running average is large (~0 Elo)
-          if (thisThread->ttHitAverage.is_greater(537, 1024))
+          // Decrease reduction if on the PV (~2 Elo)
+          if (   PvNode
+              && bestMoveCount <= 3)
               r--;
 
           // Decrease reduction if position is or has been on the PV
@@ -1314,9 +1298,11 @@ moves_loop: // When in check, search starts here
               for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m)
                   rm.pv.push_back(*m);
 
-              // We record how often the best move has been changed in each
-              // iteration. This information is used for time management and LMR
-              if (moveCount > 1)
+              // We record how often the best move has been changed in each iteration.
+              // This information is used for time management and LMR. In MultiPV mode,
+              // we must take care to only do this for the first PV line.
+              if (   moveCount > 1
+                  && !thisThread->pvIdx)
                   ++thisThread->bestMoveChanges;
           }
           else
@@ -1338,7 +1324,10 @@ moves_loop: // When in check, search starts here
                   update_pv(ss->pv, move, (ss+1)->pv);
 
               if (PvNode && value < beta) // Update alpha! Always alpha < beta
+              {
                   alpha = value;
+                  bestMoveCount++;
+              }
               else
               {
                   assert(value >= beta); // Fail high
@@ -1497,7 +1486,6 @@ moves_loop: // When in check, search starts here
         }
         else
             // In case of null move search use previous static eval with a different sign
-            // and addition of two tempos
             ss->staticEval = bestValue =
             (ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
                                              : -(ss-1)->staticEval;
@@ -1707,8 +1695,8 @@ moves_loop: // When in check, search starts here
     PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
 
     bonus1 = stat_bonus(depth + 1);
-    bonus2 = bestValue > beta + PawnValueMg ? bonus1                                 // larger bonus
-                                            : std::min(bonus1, stat_bonus(depth));   // smaller bonus
+    bonus2 = bestValue > beta + PawnValueMg ? bonus1               // larger bonus
+                                            : stat_bonus(depth);   // smaller bonus
 
     if (!pos.capture_or_promotion(bestMove))
     {