Introduce voting system for best move selection

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index e36c69593e307d17aa18bf0fe9d2d60fc1b39305..990c4123e6a91659ed0ab94baaca28a01ad8037d 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -246,18 +246,30 @@ void MainThread::search() {
       && !Skill(Options["Skill Level"]).enabled()
       &&  rootMoves[0].pv[0] != MOVE_NONE)
   {
-      for (Thread* th : Threads)
-      {
-          Depth depthDiff = th->completedDepth - bestThread->completedDepth;
-          Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score;
+      std::map<Move, int> votes;
+      Value minScore = this->rootMoves[0].score;
 
-          // Select the thread with the best score, always if it is a mate
-          if (    scoreDiff > 0
-              && (depthDiff >= 0 || th->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY))
-              bestThread = th;
+      // Find out minimum score and reset votes for moves which can be voted
+      for (Thread* th: Threads){
+          minScore = std::min(minScore, th->rootMoves[0].score);
+          votes[th->rootMoves[0].pv[0]] = 0;
+      }
+
+      // Vote according to score and depth
+      for (Thread* th : Threads)
+          votes[th->rootMoves[0].pv[0]] +=  int(th->rootMoves[0].score - minScore)  + int(th->completedDepth);
+
+      // Select best thread
+      int bestVote = votes[this->rootMoves[0].pv[0]];
+      for (Thread* th : Threads){
+          if (votes[th->rootMoves[0].pv[0]] > bestVote){
+            bestVote = votes[th->rootMoves[0].pv[0]];
+            bestThread = th;
+          }
       }
   }
 
+
   previousScore = bestThread->rootMoves[0].score;
 
   // Send again PV info if we have a new best thread