Fix endless reaparenting loop

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 7349e96b48d9c2f93372eeabe9ad2c56bc9095cb..21d5d786b6ba8be9e558bca2ffb18dfd78c951f1 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -265,7 +265,7 @@ void Search::think() {
       goto finalize;
   }
 
-  if (Options["OwnBook"])
+  if (Options["OwnBook"] && !Limits.infinite)
   {
       Move bookMove = book.probe(pos, Options["Book File"], Options["Best Book Move"]);
 
@@ -1337,7 +1337,7 @@ split_point_start: // At split points actual search starts from here
     // Rule 1. Checks which give opponent's king at most one escape square are dangerous
     b = kingAtt & ~pos.pieces(them) & ~newAtt & ~(1ULL << to);
 
-    if (single_bit(b)) // Catches also !b
+    if (!more_than_one(b))
         return true;
 
     // Rule 2. Queen contact check is very dangerous
@@ -1386,7 +1386,7 @@ split_point_start: // At split points actual search starts from here
 
     // Case 3: Moving through the vacated square
     p2 = pos.piece_on(f2);
-    if (piece_is_slider(p2) && (squares_between(f2, t2) & f1))
+    if (piece_is_slider(p2) && (between_bb(f2, t2) & f1))
       return true;
 
     // Case 4: The destination square for m2 is defended by the moving piece in m1
@@ -1397,7 +1397,7 @@ split_point_start: // At split points actual search starts from here
     // Case 5: Discovered check, checking piece is the piece moved in m1
     ksq = pos.king_square(pos.side_to_move());
     if (    piece_is_slider(p1)
-        && (squares_between(t1, ksq) & f2)
+        && (between_bb(t1, ksq) & f2)
         && (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & ksq))
         return true;
 
@@ -1469,7 +1469,7 @@ split_point_start: // At split points actual search starts from here
     // Case 3: If the moving piece in the threatened move is a slider, don't
     // prune safe moves which block its ray.
     if (    piece_is_slider(pos.piece_on(tfrom))
-        && (squares_between(tfrom, tto) & mto)
+        && (between_bb(tfrom, tto) & mto)
         &&  pos.see_sign(m) >= 0)
         return true;
 
@@ -1844,6 +1844,7 @@ void Thread::idle_loop(SplitPoint* sp_master) {
           assert(is_searching);
 
           is_searching = false;
+          sp->allSlavesRunning = false;
           sp->slavesMask &= ~(1ULL << idx);
           sp->nodes += pos.nodes_searched();
 
@@ -1859,6 +1860,43 @@ void Thread::idle_loop(SplitPoint* sp_master) {
           // our feet by the sp master. Also accessing other Thread objects is
           // unsafe because if we are exiting there is a chance are already freed.
           lock_release(sp->lock);
+
+          // Try to reparent to the first split point, with still all slaves
+          // running, where we are available as a possible slave.
+          for (int i = 0; i < Threads.size(); i++)
+          {
+              Thread* th = &Threads[i];
+              int spCnt = th->splitPointsCnt;
+              SplitPoint* latest = &th->splitPoints[spCnt ? spCnt - 1 : 0];
+
+              if (    this->is_available_to(th)
+                  &&  spCnt > 0
+                  && !th->cutoff_occurred()
+                  &&  latest->allSlavesRunning
+                  &&  more_than_one(latest->slavesMask))
+              {
+                  lock_grab(latest->lock);
+                  lock_grab(Threads.splitLock);
+
+                  // Retest all under lock protection, we are in the middle
+                  // of a race storm here !
+                  if (    this->is_available_to(th)
+                      &&  spCnt == th->splitPointsCnt
+                      && !th->cutoff_occurred()
+                      &&  latest->allSlavesRunning
+                      &&  more_than_one(latest->slavesMask))
+                  {
+                      latest->slavesMask |= 1ULL << idx;
+                      curSplitPoint = latest;
+                      is_searching = true;
+                  }
+
+                  lock_release(Threads.splitLock);
+                  lock_release(latest->lock);
+
+                  break; // Exit anyhow, only one try (enough in 99% of cases)
+              }
+          }
       }
   }
 }