X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=1f848183481a573cf59710f2993a1c4fb890a1f2;hp=4864b1cb151f70e2e1fc1849e198c9abc24802a6;hb=a90a990118fa84d1e6138654dd24d2f7f4ec3761;hpb=eabba1119f45f2ac8a3a6248bd1c1d9868d7af5c

diff --git a/src/search.cpp b/src/search.cpp
index 4864b1cb..1f848183 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -363,7 +363,7 @@ int64_t perft(Position& pos, Depth depth) {
 
 bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) {
 
-  static Book book;
+  static Book book; // Define static to initialize the PRNG only once
 
   // Initialize global search-related variables
   StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = false;
@@ -409,8 +409,7 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) {
   read_evaluation_uci_options(pos.side_to_move());
   Threads.read_uci_options();
 
-  // If needed allocate pawn and material hash tables and adjust TT size
-  Threads.init_hash_tables();
+  // Set a new TT size if changed
   TT.set_size(Options["Hash"].value<int>());
 
   if (Options["Clear Hash"].value<bool>())
@@ -535,8 +534,10 @@ namespace {
 
         Rml.bestMoveChanges = 0;
 
-        // MultiPV iteration loop
-        for (MultiPVIteration = 0; MultiPVIteration < Min(MultiPV, (int)Rml.size()); MultiPVIteration++)
+        // MultiPV iteration loop. At depth 1 perform at least 2 iterations to
+        // get a score of the second best move for easy move detection.
+        int e = Min(Max(MultiPV, 2 * int(depth == 1)), (int)Rml.size());
+        for (MultiPVIteration = 0; MultiPVIteration < e; MultiPVIteration++)
         {
             // Calculate dynamic aspiration window based on previous iterations
             if (depth >= 5 && abs(Rml[MultiPVIteration].prevScore) < VALUE_KNOWN_WIN)
@@ -779,8 +780,18 @@ namespace {
                                     : can_return_tt(tte, depth, beta, ss->ply)))
     {
         TT.refresh(tte);
-        ss->bestMove = ttMove; // Can be MOVE_NONE
-        return value_from_tt(tte->value(), ss->ply);
+        ss->bestMove = move = ttMove; // Can be MOVE_NONE
+        value = value_from_tt(tte->value(), ss->ply);
+
+        if (   value >= beta
+            && move
+            && !pos.move_is_capture_or_promotion(move)
+            && move != ss->killers[0])
+        {
+            ss->killers[1] = ss->killers[0];
+            ss->killers[0] = move;
+        }
+        return value;
     }
 
     // Step 5. Evaluate the position statically and update parent's gain statistics
@@ -1001,8 +1012,7 @@ split_point_start: // At split points actual search starts from here
                    << " currmovenumber " << moveCount + MultiPVIteration << endl;
       }
 
-      // At Root and at first iteration do a PV search on all the moves to score root moves
-      isPvMove = (PvNode && moveCount <= (RootNode && depth <= ONE_PLY ? MAX_MOVES : 1));
+      isPvMove = (PvNode && moveCount == 1);
       givesCheck = pos.move_gives_check(move, ci);
       captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
@@ -1539,8 +1549,8 @@ split_point_start: // At split points actual search starts from here
     Piece p1, p2;
     Square ksq;
 
-    assert(m1 && move_is_ok(m1));
-    assert(m2 && move_is_ok(m2));
+    assert(move_is_ok(m1));
+    assert(move_is_ok(m2));
 
     // Case 1: The moving piece is the same in both moves
     f2 = move_from(m2);
@@ -1616,7 +1626,7 @@ split_point_start: // At split points actual search starts from here
   bool connected_threat(const Position& pos, Move m, Move threat) {
 
     assert(move_is_ok(m));
-    assert(threat && move_is_ok(threat));
+    assert(move_is_ok(threat));
     assert(!pos.move_is_capture_or_promotion(m));
     assert(!pos.move_is_passed_pawn_push(m));
 
@@ -2129,71 +2139,70 @@ split_point_start: // At split points actual search starts from here
 } // namespace
 
 
-// ThreadsManager::idle_loop() is where the threads are parked when they have no work
-// to do. The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
-// object for which the current thread is the master.
+// Little helper used by idle_loop() to check that all the slave threads of a
+// split point have finished searching.
+
+static bool all_slaves_finished(SplitPoint* sp) {
+
+  for (int i = 0; i < Threads.size(); i++)
+      if (sp->is_slave[i])
+          return false;
+
+  return true;
+}
 
-void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
 
-  assert(threadID >= 0 && threadID < MAX_THREADS);
+// Thread::idle_loop() is where the thread is parked when it has no work to do.
+// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
+// for which the thread is the master.
 
-  int i;
-  bool allFinished;
+void Thread::idle_loop(SplitPoint* sp) {
 
   while (true)
   {
-      // Slave threads can exit as soon as AllThreadsShouldExit raises,
-      // master should exit as last one.
-      if (allThreadsShouldExit)
-      {
-          assert(!sp);
-          threads[threadID].state = Thread::TERMINATED;
-          return;
-      }
-
-      // If we are not thinking, wait for a condition to be signaled
+      // If we are not searching, wait for a condition to be signaled
       // instead of wasting CPU time polling for work.
-      while (   threadID >= activeThreads
-             || threads[threadID].state == Thread::INITIALIZING
-             || (useSleepingThreads && threads[threadID].state == Thread::AVAILABLE))
+      while (   do_sleep
+             || do_terminate
+             || (Threads.use_sleeping_threads() && !is_searching))
       {
-          assert(!sp || useSleepingThreads);
-          assert(threadID != 0 || useSleepingThreads);
+          assert((!sp && threadID) || Threads.use_sleeping_threads());
 
-          if (threads[threadID].state == Thread::INITIALIZING)
-              threads[threadID].state = Thread::AVAILABLE;
+          // Slave thread should exit as soon as do_terminate flag raises
+          if (do_terminate)
+          {
+              assert(!sp);
+              return;
+          }
 
           // Grab the lock to avoid races with Thread::wake_up()
-          lock_grab(&threads[threadID].sleepLock);
-
-          // If we are master and all slaves have finished do not go to sleep
-          for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
-          allFinished = (i == activeThreads);
+          lock_grab(&sleepLock);
 
-          if (allFinished || allThreadsShouldExit)
+          // If we are master and all slaves have finished don't go to sleep
+          if (sp && all_slaves_finished(sp))
           {
-              lock_release(&threads[threadID].sleepLock);
+              lock_release(&sleepLock);
               break;
           }
 
-          // Do sleep here after retesting sleep conditions
-          if (threadID >= activeThreads || threads[threadID].state == Thread::AVAILABLE)
-              cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock);
+          // Do sleep after retesting sleep conditions under lock protection, in
+          // particular we need to avoid a deadlock in case a master thread has,
+          // in the meanwhile, allocated us and sent the wake_up() call before we
+          // had the chance to grab the lock.
+          if (do_sleep || !is_searching)
+              cond_wait(&sleepCond, &sleepLock);
 
-          lock_release(&threads[threadID].sleepLock);
+          lock_release(&sleepLock);
       }
 
       // If this thread has been assigned work, launch a search
-      if (threads[threadID].state == Thread::WORKISWAITING)
+      if (is_searching)
       {
-          assert(!allThreadsShouldExit);
-
-          threads[threadID].state = Thread::SEARCHING;
+          assert(!do_terminate);
 
           // Copy split point position and search stack and call search()
-          // with SplitPoint template parameter set to true.
           SearchStack ss[PLY_MAX_PLUS_2];
-          SplitPoint* tsp = threads[threadID].splitPoint;
+          SplitPoint* tsp = splitPoint;
           Position pos(*tsp->pos, threadID);
 
           memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
@@ -2208,33 +2217,26 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
           else
               assert(false);
 
-          assert(threads[threadID].state == Thread::SEARCHING);
+          assert(is_searching);
 
-          threads[threadID].state = Thread::AVAILABLE;
+          is_searching = false;
 
           // Wake up master thread so to allow it to return from the idle loop in
           // case we are the last slave of the split point.
-          if (   useSleepingThreads
+          if (   Threads.use_sleeping_threads()
               && threadID != tsp->master
-              && threads[tsp->master].state == Thread::AVAILABLE)
-              threads[tsp->master].wake_up();
+              && !Threads[tsp->master].is_searching)
+              Threads[tsp->master].wake_up();
       }
 
       // 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.
-      for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
-      allFinished = (i == activeThreads);
-
-      if (allFinished)
+      if (sp && all_slaves_finished(sp))
       {
-          // Because sp->slaves[] is reset under lock protection,
+          // Because sp->is_slave[] is reset under lock protection,
           // be sure sp->lock has been released before to return.
           lock_grab(&(sp->lock));
           lock_release(&(sp->lock));
-
-          // In helpful master concept a master can help only a sub-tree, and
-          // because here is all finished is not possible master is booked.
-          assert(threads[threadID].state == Thread::AVAILABLE);
           return;
       }
   }