Make use of asymmetric SEE

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c5c5b94470fed9365831fea28427db4d4070d0e5..ab34673463c57286d7ec4047a46755d6fc24701e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -44,7 +44,6 @@ namespace Search {
   Color RootColor;
   Time::point SearchTime;
   StateStackPtr SetupStates;
-  MovesVectPtr SetupMoves;
 }
 
 using std::string;
@@ -294,7 +293,6 @@ namespace {
     Stack ss[MAX_PLY_PLUS_2];
     int depth, prevBestMoveChanges;
     Value bestValue, alpha, beta, delta;
-    bool bestMoveNeverChanged = true;
 
     memset(ss, 0, 4 * sizeof(Stack));
     depth = BestMoveChanges = 0;
@@ -417,10 +415,6 @@ namespace {
                 << std::endl;
         }
 
-        // Filter out startup noise when monitoring best move stability
-        if (depth > 2 && BestMoveChanges)
-            bestMoveNeverChanged = false;
-
         // Do we have found a "mate in x"?
         if (   Limits.mate
             && bestValue >= VALUE_MATE_IN_MAX_PLY
@@ -442,18 +436,13 @@ namespace {
             if (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100)
                 stop = true;
 
-            bool recapture =   pos.is_capture(RootMoves[0].pv[0])
-                            && pos.captured_piece_type()
-                            && SetupMoves->size()
-                            && to_sq(SetupMoves->back()) == to_sq(RootMoves[0].pv[0]);
-
             // Stop search early if one move seems to be much better than others
             if (    depth >= 12
                 && !stop
                 &&  PVSize == 1
-                && (   (bestMoveNeverChanged && recapture)
-                    || RootMoves.size() == 1
-                    || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100))
+                &&  bestValue > VALUE_MATED_IN_MAX_PLY
+                && (   RootMoves.size() == 1
+                    || Time::now() - SearchTime > (TimeMgr.available_time() * 20) / 100))
             {
                 Value rBeta = bestValue - 2 * PawnValueMg;
                 (ss+1)->excludedMove = RootMoves[0].pv[0];
@@ -757,7 +746,7 @@ namespace {
         && ttMove == MOVE_NONE
         && (PvNode || (!inCheck && ss->staticEval + Value(256) >= beta)))
     {
-        Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
+        Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
 
         ss->skipNullMove = true;
         search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);
@@ -864,14 +853,15 @@ split_point_start: // At split points actual search starts from here
       newDepth = depth - ONE_PLY + ext;
 
       // Step 13. Futility pruning (is omitted in PV nodes)
-      if (   !captureOrPromotion
+      if (   !PvNode
+          && !captureOrPromotion
           && !inCheck
           && !dangerous
-          &&  move != ttMove)
+          &&  move != ttMove
+          &&  bestValue > VALUE_MATED_IN_MAX_PLY)
       {
           // Move count based pruning
-          if (   !PvNode
-              && depth < 16 * ONE_PLY
+          if (   depth < 16 * ONE_PLY
               && moveCount >= FutilityMoveCounts[depth]
               && (!threatMove || !refutes(pos, move, threatMove)))
           {
@@ -888,16 +878,21 @@ split_point_start: // At split points actual search starts from here
           futilityValue =  ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount)
                          + Gain[pos.piece_moved(move)][to_sq(move)];
 
-          if (!PvNode && futilityValue < beta)
+          if (futilityValue < beta)
           {
+              bestValue = std::max(bestValue, futilityValue);
+
               if (SpNode)
+              {
                   splitPoint->mutex.lock();
-
+                  if (bestValue > splitPoint->bestValue)
+                      splitPoint->bestValue = bestValue;
+              }
               continue;
           }
 
           // Prune moves with negative SEE at low depths
-          if (   predictedDepth < 2 * ONE_PLY
+          if (   predictedDepth < 4 * ONE_PLY
               && pos.see_sign(move) < 0)
           {
               if (SpNode)
@@ -1137,6 +1132,12 @@ split_point_start: // At split points actual search starts from here
     if (pos.is_draw<true>() || ss->ply > MAX_PLY)
         return DrawValue[pos.side_to_move()];
 
+    // Decide whether or not to include checks, this fixes also the type of
+    // TT entry depth that we are going to use. Note that in qsearch we use
+    // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
+    ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
+                                                  : DEPTH_QS_NO_CHECKS;
+
     // Transposition table lookup. At PV nodes, we don't use the TT for
     // pruning, but only for move ordering.
     posKey = pos.key();
@@ -1144,11 +1145,6 @@ split_point_start: // At split points actual search starts from here
     ttMove = tte ? tte->move() : MOVE_NONE;
     ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
 
-    // Decide whether or not to include checks, this fixes also the type of
-    // TT entry depth that we are going to use. Note that in qsearch we use
-    // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
-    ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
-                                                  : DEPTH_QS_NO_CHECKS;
     if (   tte
         && tte->depth() >= ttDepth
         && ttValue != VALUE_NONE // Only in case of TT access race
@@ -1232,7 +1228,7 @@ split_point_start: // At split points actual search starts from here
           // Prune moves with negative or equal SEE
           if (   futilityBase < beta
               && depth < DEPTH_ZERO
-              && pos.see(move) <= 0)
+              && pos.see_asymm(move, beta - futilityBase) <= 0)
           {
               bestValue = std::max(bestValue, futilityBase);
               continue;
@@ -1626,13 +1622,8 @@ void Thread::idle_loop() {
 
   assert(!this_sp || (this_sp->masterThread == this && searching));
 
-  // If this thread is the master of a split point and all slaves have finished
-  // their work at this split point, return from the idle loop.
-  while (!this_sp || this_sp->slavesMask)
+  while (true)
   {
-      if (this_sp)
-          this_sp->mutex.unlock();
-
       // If we are not searching, wait for a condition to be signaled instead of
       // wasting CPU time polling for work.
       while ((!searching && Threads.sleepWhileIdle) || exit)
@@ -1725,8 +1716,16 @@ void Thread::idle_loop() {
           sp->mutex.unlock();
       }
 
-      if(this_sp)
+      // If this thread is the master of a split point and all slaves have finished
+      // their work at this split point, return from the idle loop.
+      if (this_sp && !this_sp->slavesMask)
+      {
           this_sp->mutex.lock();
+          bool finished = !this_sp->slavesMask; // Retest under lock protection
+          this_sp->mutex.unlock();
+          if (finished)
+              return;
+      }
   }
 }