Correctly output lowerbound/upperbound in threaded searches

fixes the lowerbound/upperbound output by taking the alpha,beta bracket
into account also if a bestThread is selected that is different from the master thread.

Instead of keeping track which bounds where used in the specific search,
in this version we simply store the quality (exact, upperbound,
lowerbound) of the score along with the actual score as information on
rootMove.

closes https://github.com/official-stockfish/Stockfish/pull/4239

No functional change

diff --git a/src/search.cpp b/src/search.cpp
index e73f68ffb0aba1a9499fbb0cd09941a03a3148a5..b3f60f3d15bcff7750b283d0bd3346f7828733c4 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -244,7 +244,7 @@ void MainThread::search() {
 
   // Send again PV info if we have a new best thread
   if (bestThread != this)
-      sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl;
+      sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth) << sync_endl;
 
   sync_cout << "bestmove " << UCI::move(bestThread->rootMoves[0].pv[0], rootPos.is_chess960());
 
@@ -392,7 +392,7 @@ void Thread::search() {
                   && multiPV == 1
                   && (bestValue <= alpha || bestValue >= beta)
                   && Time.elapsed() > 3000)
-                  sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
+                  sync_cout << UCI::pv(rootPos, rootDepth) << sync_endl;
 
               // In case of failing low/high increase aspiration window and
               // re-search, otherwise exit the loop.
@@ -423,7 +423,7 @@ void Thread::search() {
 
           if (    mainThread
               && (Threads.stop || pvIdx + 1 == multiPV || Time.elapsed() > 3000))
-              sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
+              sync_cout << UCI::pv(rootPos, rootDepth) << sync_endl;
       }
 
       if (!Threads.stop)
@@ -1246,6 +1246,8 @@ moves_loop: // When in check, search starts here
           {
               rm.score = value;
               rm.selDepth = thisThread->selDepth;
+              rm.scoreLowerbound = value >= beta;
+              rm.scoreUpperbound = value <= alpha;
               rm.pv.resize(1);
 
               assert((ss+1)->pv);
@@ -1820,7 +1822,7 @@ void MainThread::check_time() {
 /// UCI::pv() formats PV information according to the UCI protocol. UCI requires
 /// that all (if any) unsearched PV lines are sent using a previous search score.
 
-string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
+string UCI::pv(const Position& pos, Depth depth) {
 
   std::stringstream ss;
   TimePoint elapsed = Time.elapsed() + 1;
@@ -1858,8 +1860,8 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
       if (Options["UCI_ShowWDL"])
           ss << UCI::wdl(v, pos.game_ply());
 
-      if (!tb && i == pvIdx)
-          ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
+      if (i == pvIdx && !tb && updated) // tablebase- and previous-scores are exact
+         ss << (rootMoves[i].scoreLowerbound ? " lowerbound" : (rootMoves[i].scoreUpperbound ? " upperbound" : ""));
 
       ss << " nodes "    << nodesSearched
          << " nps "      << nodesSearched * 1000 / elapsed

diff --git a/src/search.h b/src/search.h
index f264bcae84027972c52511f6e02fe5c67eb0c889..60f2762a6f499044c17764910e6fd41bbf2aadd5 100644 (file)
--- a/src/search.h
+++ b/src/search.h
@@ -71,6 +71,8 @@ struct RootMove {
   Value score = -VALUE_INFINITE;
   Value previousScore = -VALUE_INFINITE;
   Value averageScore = -VALUE_INFINITE;
+  bool scoreLowerbound = false;
+  bool scoreUpperbound = false;
   int selDepth = 0;
   int tbRank = 0;
   Value tbScore;

diff --git a/src/uci.h b/src/uci.h
index 7a2ef2558186fae68414871dfb14e2168332e313..3b5a6764b48c8897cf0392689dae131bc81dfa31 100644 (file)
--- a/src/uci.h
+++ b/src/uci.h
@@ -79,7 +79,7 @@ void loop(int argc, char* argv[]);
 std::string value(Value v);
 std::string square(Square s);
 std::string move(Move m, bool chess960);
-std::string pv(const Position& pos, Depth depth, Value alpha, Value beta);
+std::string pv(const Position& pos, Depth depth);
 std::string wdl(Value v, int ply);
 Move to_move(const Position& pos, std::string& str);