Lower SingularExtensionDepth to 7 plies for non-pv

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 35565d87841b083bb8527aac4c01520e98942bc3..588f76f3e6b789c6d8d500c56aba12eaf61718c7 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -198,7 +198,7 @@ namespace {
   Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
 
   // Minimum depth for use of singular extension
-  const Depth SingularExtensionDepth[2] = { 8 * OnePly /* non-PV */, 6 * OnePly /* PV */};
+  const Depth SingularExtensionDepth[2] = { 7 * OnePly /* non-PV */, 6 * OnePly /* PV */};
 
   // If the TT move is at least SingularExtensionMargin better then the
   // remaining ones we will extend it.
@@ -360,20 +360,6 @@ void init_search() {
 }
 
 
-// SearchStack::init() initializes a search stack entry.
-// Called at the beginning of search() when starting to examine a new node.
-void SearchStack::init() {
-
-  currentMove = bestMove = MOVE_NONE;
-}
-
-// SearchStack::initKillers() initializes killers for a search stack entry
-void SearchStack::initKillers() {
-
-  killers[0] = killers[1] = mateKiller = MOVE_NONE;
-}
-
-
 /// perft() is our utility to verify move generation is bug free. All the legal
 /// moves up to given depth are generated and counted and the sum returned.
 
@@ -763,7 +749,7 @@ namespace {
     isCheck = pos.is_check();
 
     // Step 1. Initialize node (polling is omitted at root)
-    ss->init();
+    ss->currentMove = ss->bestMove = MOVE_NONE;
 
     // Step 2. Check for aborted search (omitted at root)
     // Step 3. Mate distance pruning (omitted at root)
@@ -1018,7 +1004,7 @@ namespace {
     StateInfo st;
     const TTEntry* tte;
     Key posKey;
-    Move ttMove, move, excludedMove;
+    Move ttMove, move, excludedMove, threatMove;
     Depth ext, newDepth;
     Value bestValue, value, oldAlpha;
     Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific
@@ -1026,14 +1012,13 @@ namespace {
     bool mateThreat = false;
     int moveCount = 0;
     int threadID = pos.thread();
-    Move threatMove = MOVE_NONE;
     refinedValue = bestValue = value = -VALUE_INFINITE;
     oldAlpha = alpha;
 
     // Step 1. Initialize node and poll. Polling can abort search
     TM.incrementNodeCounter(threadID);
-    ss->init();
-    (ss+2)->initKillers();
+    ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
+    (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
 
     if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
     {
@@ -1228,6 +1213,17 @@ namespace {
                            && is_lower_bound(tte->type())
                            && tte->depth() >= depth - 3 * OnePly;
 
+    // Avoid to do an expensive singular extension search on nodes where
+    // such search had already failed in the past.
+    if (  !PvNode
+        && singularExtensionNode
+        && depth < SingularExtensionDepth[PvNode] + 5 * OnePly)
+    {
+        TTEntry* ttx = TT.retrieve(pos.get_exclusion_key());
+        if (ttx && is_lower_bound(ttx->type()))
+            singularExtensionNode = false;
+    }
+
     // Step 10. Loop through moves
     // Loop through all legal moves until no moves remain or a beta cutoff occurs
     while (   bestValue < beta
@@ -2214,7 +2210,7 @@ namespace {
         ss->reduction = Depth(0);
 
         if (i < 3)
-            ss->initKillers();
+            ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
     }
   }
 
@@ -2485,8 +2481,8 @@ namespace {
 #endif
 
     // Initialize global locks
-    lock_init(&MPLock, NULL);
-    lock_init(&WaitLock, NULL);
+    lock_init(&MPLock);
+    lock_init(&WaitLock);
 
 #if !defined(_MSC_VER)
     pthread_cond_init(&WaitCond, NULL);
@@ -2498,7 +2494,7 @@ namespace {
     // Initialize splitPoints[] locks
     for (i = 0; i < MAX_THREADS; i++)
         for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
-            lock_init(&(threads[i].splitPoints[j].lock), NULL);
+            lock_init(&(threads[i].splitPoints[j].lock));
 
     // Will be set just before program exits to properly end the threads
     AllThreadsShouldExit = false;
@@ -2792,7 +2788,7 @@ namespace {
 
     // Initialize search stack
     init_ss_array(ss, PLY_MAX_PLUS_2);
-    ss[0].init();
+    ss[0].currentMove = ss[0].bestMove = MOVE_NONE;
     ss[0].eval = VALUE_NONE;
 
     // Generate all legal moves