Fix some races in SMP code

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 2c4d5ece2eb237f861890d7ac4add6c1c8c273ed..65c29bf3741a395f90ba2b703b9a01b4255c3865 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -193,9 +193,6 @@ namespace {
 
   /// Variables initialized by UCI options
 
-  // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV nodes
-  int LMRPVMoves, LMRNonPVMoves;
-
   // Depth limit for use of dynamic threat detection
   Depth ThreatDepth;
 
@@ -426,8 +423,6 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move,
   MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
   MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
 
-  LMRPVMoves    = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
-  LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
   ThreatDepth   = get_option_value_int("Threat Depth") * OnePly;
 
   Chess960 = get_option_value_bool("UCI_Chess960");
@@ -566,7 +561,7 @@ void init_threads() {
 #endif
 
   // Init our logarithmic lookup table
-  for (int i = 0; i < 512; i++)
+  for (i = 0; i < 512; i++)
       lnArray[i] = log(double(i)); // log() returns base-e logarithm
 
   for (i = 0; i < THREAD_MAX; i++)
@@ -835,7 +830,7 @@ namespace {
 
     // If we are pondering or in infinite search, we shouldn't print the
     // best move before we are told to do so.
-    if (!AbortSearch && (PonderSearch || InfiniteSearch))
+    if (!AbortSearch && !ExactMaxTime && (PonderSearch || InfiniteSearch))
         wait_for_stop_or_ponderhit();
     else
         // Print final search statistics
@@ -1692,10 +1687,14 @@ namespace {
     if (bestValue > alpha)
         alpha = bestValue;
 
+    // If we are near beta then try to get a cutoff pushing checks a bit further
+    bool deepChecks = depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8;
+
     // Initialize a MovePicker object for the current position, and prepare
-    // to search the moves.  Because the depth is <= 0 here, only captures,
-    // queen promotions and checks (only if depth == 0) will be generated.
-    MovePicker mp = MovePicker(pos, ttMove, depth, H);
+    // to search the moves. Because the depth is <= 0 here, only captures,
+    // queen promotions and checks (only if depth == 0 or depth == -OnePly
+    // and we are near beta) will be generated.
+    MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H);
     CheckInfo ci(pos);
     enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
     futilityBase = staticValue + FutilityMarginQS + ei.futilityMargin;
@@ -2010,7 +2009,14 @@ namespace {
               if (sp->ply == 1 && RootMoveNumber == 1)
                   Threads[threadID].failHighPly1 = true;
 
-              value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, threadID);
+              // If another thread has failed high then sp->alpha has been increased
+              // to be higher or equal then beta, if so, avoid to start a PV search.
+              localAlpha = sp->alpha;
+              if (localAlpha < sp->beta)
+                  value = -search_pv(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, threadID);
+              else
+                  assert(thread_should_stop(threadID));
+
               Threads[threadID].failHighPly1 = false;
         }
       }
@@ -2028,11 +2034,7 @@ namespace {
           sp->bestValue = value;
           if (value > sp->alpha)
           {
-              sp->alpha = value;
-              sp_update_pv(sp->parentSstack, ss, sp->ply);
-              if (value == value_mate_in(sp->ply + 1))
-                  ss[sp->ply].mateKiller = move;
-
+              // Ask threads to stop before to modify sp->alpha
               if (value >= sp->beta)
               {
                   for (int i = 0; i < ActiveThreads; i++)
@@ -2041,6 +2043,12 @@ namespace {
 
                   sp->finished = true;
               }
+
+              sp->alpha = value;
+
+              sp_update_pv(sp->parentSstack, ss, sp->ply);
+              if (value == value_mate_in(sp->ply + 1))
+                  ss[sp->ply].mateKiller = move;
         }
         // If we are at ply 1, and we are searching the first root move at
         // ply 0, set the 'Problem' variable if the score has dropped a lot