Fix repetition detection bug

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index a052ea18f8828d3c56c8dc8cee94c0cde34bcbcc..eddf4ea93813e24d89312cc7549bef3f6fb3dc66 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1790,6 +1790,7 @@ namespace {
     Position pos(*sp->pos);
     CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
+    StateInfo st;
     Value value = -VALUE_INFINITE;
     Move move;
     int moveCount;
@@ -1797,8 +1798,9 @@ namespace {
     bool useFutilityPruning =     sp->depth < 7 * OnePly //FIXME: sync with search
                               && !isCheck;
 
-    while (    lock_grab_bool(&(sp->lock))
-           &&  sp->bestValue < sp->beta
+    lock_grab(&(sp->lock));
+
+    while (    sp->bestValue < sp->beta
            && !TM.thread_should_stop(threadID)
            && (move = sp->mp->get_next_move()) != MOVE_NONE)
     {
@@ -1826,29 +1828,28 @@ namespace {
           if (   moveCount >= futility_move_count(sp->depth)
               && ok_to_prune(pos, move, ss[sp->ply].threatMove)
               && sp->bestValue > value_mated_in(PLY_MAX))
+          {
+              lock_grab(&(sp->lock));
               continue;
+          }
 
           // Value based pruning
           Value futilityValueScaled = sp->futilityValue - moveCount * 8; //FIXME: sync with search
 
           if (futilityValueScaled < sp->beta)
           {
-              if (futilityValueScaled > sp->bestValue) // Less then 1% of cases
-              {
-                  lock_grab(&(sp->lock));
-                  if (futilityValueScaled > sp->bestValue)
-                      sp->bestValue = futilityValueScaled;
-                  lock_release(&(sp->lock));
-              }
+              lock_grab(&(sp->lock));
+
+              if (futilityValueScaled > sp->bestValue)
+                  sp->bestValue = futilityValueScaled;
               continue;
           }
       }
 
-      // Make and search the move.
-      StateInfo st;
+      // Step 13. Make the move
       pos.do_move(move, st, ci, moveIsCheck);
 
-      // Try to reduce non-pv search depth by one ply if move seems not problematic,
+      // Step 14. Reduced search
       // if the move fails high will be re-searched at full depth.
       bool doFullDepthSearch = true;
 
@@ -1865,36 +1866,36 @@ namespace {
           }
       }
 
-      if (doFullDepthSearch) // Go with full depth non-pv search
+      // Step 15. Full depth search
+      if (doFullDepthSearch)
       {
           ss[sp->ply].reduction = Depth(0);
           value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
       }
+
+      // Step 16. Undo move
       pos.undo_move(move);
 
       assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
 
-      // New best move?
-      if (value > sp->bestValue) // Less then 2% of cases
+      // Step 17. Check for new best move
+      lock_grab(&(sp->lock));
+
+      if (value > sp->bestValue && !TM.thread_should_stop(threadID))
       {
-          lock_grab(&(sp->lock));
-          if (value > sp->bestValue && !TM.thread_should_stop(threadID))
+          sp->bestValue = value;
+          if (sp->bestValue >= sp->beta)
           {
-              sp->bestValue = value;
-              if (sp->bestValue >= sp->beta)
-              {
-                  sp->stopRequest = true;
-                  sp_update_pv(sp->parentSstack, ss, sp->ply);
-              }
+              sp->stopRequest = true;
+              sp_update_pv(sp->parentSstack, ss, sp->ply);
           }
-          lock_release(&(sp->lock));
       }
     }
 
     /* Here we have the lock still grabbed */
 
-    sp->cpus--;
     sp->slaves[threadID] = 0;
+    sp->cpus--;
 
     lock_release(&(sp->lock));
   }
@@ -1916,12 +1917,16 @@ namespace {
     Position pos(*sp->pos);
     CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
+    StateInfo st;
     Value value = -VALUE_INFINITE;
     int moveCount;
     Move move;
 
-    while (    lock_grab_bool(&(sp->lock))
-           &&  sp->alpha < sp->beta
+    // Step 10. Loop through moves
+    // Loop through all legal moves until no moves remain or a beta cutoff occurs
+    lock_grab(&(sp->lock));
+
+    while (    sp->alpha < sp->beta
            && !TM.thread_should_stop(threadID)
            && (move = sp->mp->get_next_move()) != MOVE_NONE)
     {
@@ -1933,18 +1938,20 @@ namespace {
       bool moveIsCheck = pos.move_is_check(move, ci);
       bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
 
-      ss[sp->ply].currentMove = move;
-
-      // Decide the new search depth
+      // Step 11. Decide the new search depth
       bool dangerous;
       Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
       Depth newDepth = sp->depth - OnePly + ext;
 
-      // Make and search the move.
-      StateInfo st;
+      // Update current move
+      ss[sp->ply].currentMove = move;
+
+      // Step 12. Futility pruning (is omitted in PV nodes)
+
+      // Step 13. Make the move
       pos.do_move(move, st, ci, moveIsCheck);
 
-      // Try to reduce non-pv search depth by one ply if move seems not problematic,
+      // Step 14. Reduced search
       // if the move fails high will be re-searched at full depth.
       bool doFullDepthSearch = true;
 
@@ -1962,7 +1969,8 @@ namespace {
           }
       }
 
-      if (doFullDepthSearch) // Go with full depth non-pv search
+      // Step 15. Full depth search
+      if (doFullDepthSearch)
       {
           Value localAlpha = sp->alpha;
           ss[sp->ply].reduction = Depth(0);
@@ -1977,38 +1985,37 @@ namespace {
                   value = -search_pv(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, threadID);
           }
       }
+
+      // Step 16. Undo move
       pos.undo_move(move);
 
       assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
 
-      // New best move?
-      if (value > sp->bestValue) // Less then 2% of cases
+      // Step 17. Check for new best move
+      lock_grab(&(sp->lock));
+
+      if (value > sp->bestValue && !TM.thread_should_stop(threadID))
       {
-          lock_grab(&(sp->lock));
-          if (value > sp->bestValue && !TM.thread_should_stop(threadID))
+          sp->bestValue = value;
+          if (value > sp->alpha)
           {
-              sp->bestValue = value;
-              if (value > sp->alpha)
-              {
-                  // Ask threads to stop before to modify sp->alpha
-                  if (value >= sp->beta)
-                      sp->stopRequest = 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;
-              }
+              // Ask threads to stop before to modify sp->alpha
+              if (value >= sp->beta)
+                  sp->stopRequest = 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;
           }
-          lock_release(&(sp->lock));
       }
     }
 
     /* Here we have the lock still grabbed */
 
-    sp->cpus--;
     sp->slaves[threadID] = 0;
+    sp->cpus--;
 
     lock_release(&(sp->lock));
   }