Fix issue #1268

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 07c18012739e5b681f662ed08121650d01a9502f..f0224d8c72d3d9fdba241800fde5b3feac540b69 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -87,10 +87,9 @@ namespace {
 
   // Skill structure is used to implement strength limit
   struct Skill {
-    Skill(int l) : level(l) {}
+    explicit Skill(int l) : level(l) {}
     bool enabled() const { return level < 20; }
     bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
-    Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); }
     Move pick_best(size_t multiPV);
 
     int level;
@@ -259,11 +258,6 @@ void MainThread::search() {
       Thread::search(); // Let's start searching!
   }
 
-  // When playing in 'nodes as time' mode, subtract the searched nodes from
-  // the available ones before exiting.
-  if (Limits.npmsec)
-      Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
-
   // When we reach the maximum depth, we can arrive here without a raise of
   // Threads.stop. However, if we are pondering or in an infinite search,
   // the UCI protocol states that we shouldn't print the best move before the
@@ -283,6 +277,11 @@ void MainThread::search() {
       if (th != this)
           th->wait_for_search_finished();
 
+  // When playing in 'nodes as time' mode, subtract the searched nodes from
+  // the available ones before exiting.
+  if (Limits.npmsec)
+      Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
+
   // Check if there are threads with a better score than main thread
   Thread* bestThread = this;
   if (   !this->easyMovePlayed
@@ -514,8 +513,8 @@ void Thread::search() {
 
   // If skill level is enabled, swap best PV line with the sub-optimal one
   if (skill.enabled())
-      std::swap(rootMoves[0], *std::find(rootMoves.begin(),
-                rootMoves.end(), skill.best_move(multiPV)));
+      std::swap(rootMoves[0], *std::find(rootMoves.begin(), rootMoves.end(),
+                skill.best ? skill.best : skill.pick_best(multiPV)));
 }
 
 
@@ -543,7 +542,7 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
     Piece movedPiece;
     int moveCount, quietCount;
 
@@ -813,6 +812,7 @@ moves_loop: // When in check search starts from here
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
     skipQuiets = false;
     ttCapture = false;
+    pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT;
 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
@@ -957,6 +957,10 @@ moves_loop: // When in check search starts from here
               if ((ss-1)->moveCount > 15)
                   r -= ONE_PLY;
 
+              // Decrease reduction for exact PV nodes
+              if (pvExact)
+                  r -= ONE_PLY;
+
               // Increase reduction if ttMove is a capture
               if (ttCapture)
                   r += ONE_PLY;
@@ -1446,7 +1450,7 @@ moves_loop: // When in check search starts from here
         int push = (  weakness * int(topScore - rootMoves[i].score)
                     + delta * (rng.rand<unsigned>() % weakness)) / 128;
 
-        if (rootMoves[i].score + push > maxScore)
+        if (rootMoves[i].score + push >= maxScore)
         {
             maxScore = rootMoves[i].score + push;
             best = rootMoves[i].pv[0];