Do not modify alpha in split()

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 833bbba4e6f3b5d4fca4c3b2e3c35065bbb76edd..b39bc1764dbda697e8a4d19985abd435a8f3c61c 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -560,7 +560,8 @@ namespace {
             // Start with a small aspiration window and, in case of fail high/low,
             // research with bigger window until not failing high/low anymore.
             do {
-                // Search starting from ss+1 to allow calling update_gains()
+                // Search starting from ss+1 to allow referencing (ss-1). This is
+                // needed by update_gains() and ss copy when splitting at Root.
                 value = search<Root>(pos, ss+1, alpha, beta, depth * ONE_PLY);
 
                 // It is critical that sorting is done with a stable algorithm
@@ -1170,7 +1171,6 @@ split_point_start: // At split points actual search starts from here
           alpha = sp->alpha;
       }
 
-
       // Finished searching the move. If StopRequest is true, the search
       // was aborted because the user interrupted the search or because we
       // ran out of time. In this case, the return value of the search cannot
@@ -1228,8 +1228,8 @@ split_point_start: // At split points actual search starts from here
           && Threads.available_slave_exists(pos.thread())
           && !StopRequest
           && !thread.cutoff_occurred())
-          Threads.split<FakeSplit>(pos, ss, &alpha, beta, &bestValue, depth,
-                                   threatMove, moveCount, &mp, NT);
+          bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, depth,
+                                               threatMove, moveCount, &mp, NT);
     }
 
     // Step 20. Check for mate and stalemate
@@ -2211,6 +2211,8 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
               search<SplitPointPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
           else if (tsp->nodeType == NonPV)
               search<SplitPointNonPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+          else
+              assert(false);
 
           assert(threads[threadID].state == Thread::SEARCHING);
 
@@ -2239,8 +2241,6 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
           // 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);
-
-          threads[threadID].state = Thread::SEARCHING;
           return;
       }
   }