To ensure MakeTerminal value overwrites any MCTS calculated value

src/mcts/node.cc

@@ -216,15 +216,17 @@ std::string Node::DebugString() const {
   return oss.str();
 }
 
-void Node::MakeTerminal(GameResult result) {
-  is_terminal_ = true;
-  if (result == GameResult::DRAW) {
-    q_ = 0.0f;
-  } else if (result == GameResult::WHITE_WON) {
-    q_ = 1.0f;
-  } else if (result == GameResult::BLACK_WON) {
-    q_ = -1.0f;
-  }
+void Node::MakeTerminal(GameResult result, int depth) {
+	is_terminal_ = true;
+	if (result == GameResult::DRAW) {
+		q_ = 0.0f;
+	}
+	else if (result == GameResult::WHITE_WON) {
+		q_ = 10.0f - (depth / 50.0f);
+	}
+	else if (result == GameResult::BLACK_WON) {
+		q_ = -10.0f + (depth / 50.0f);
+	}
 }
 
 bool Node::TryStartScoreUpdate() {
@@ -240,8 +242,10 @@ void Node::CancelScoreUpdate(int multivisit) {
 
 void Node::FinalizeScoreUpdate(float v, int multivisit) {
   // Recompute Q.
-  q_ += multivisit * (v - q_) / (n_ + multivisit);
-  // If first visit, update parent's sum of policies visited at least once.
+	if (q_ > -0.98f && q_ < 0.98f) { // keep terminal values of -1 and 1 when found
+		q_ += multivisit * (v - q_) / (n_ + multivisit);
+  }
+	// If first visit, update parent's sum of policies visited at least once.
   if (n_ == 0 && parent_ != nullptr) {
     parent_->visited_policy_ += parent_->edges_[index_].GetP();
   }

src/mcts/node.h

@@ -160,7 +160,7 @@ class Node {
   uint16_t GetNumEdges() const { return edges_.size(); }
 
   // Makes the node terminal and sets it's score.
-  void MakeTerminal(GameResult result);
+  void MakeTerminal(GameResult result, int depth);
 
   // If this node is not in the process of being expanded by another thread
   // (which can happen only if n==0 and n-in-flight==1), mark the node as

src/mcts/search.cc

@@ -857,8 +857,7 @@ SearchWorker::NodeToProcess SearchWorker::PickNodeToExtend(
     // Either terminal or unexamined leaf node -- the end of this playout.
     if (!node->HasChildren()) {
       if (node->IsTerminal()) {
-        IncrementNInFlight(node, search_->root_node_, collision_limit - 1);
-        return NodeToProcess::TerminalHit(node, depth, collision_limit);
+        return NodeToProcess::TerminalHit(node, depth, 1);
       } else {
         return NodeToProcess::Extension(node, depth);
       }
@@ -968,9 +967,9 @@ void SearchWorker::ExtendNode(Node* node) {
   if (legal_moves.empty()) {
     // Could be a checkmate or a stalemate
     if (board.IsUnderCheck()) {
-      node->MakeTerminal(GameResult::WHITE_WON);
+      node->MakeTerminal(GameResult::WHITE_WON, search_->played_history_.GetLength());
     } else {
-      node->MakeTerminal(GameResult::DRAW);
+      node->MakeTerminal(GameResult::DRAW, search_->played_history_.GetLength());
     }
     return;
   }
@@ -979,17 +978,17 @@ void SearchWorker::ExtendNode(Node* node) {
   // if they are root, then thinking about them is the point.
   if (node != search_->root_node_) {
     if (!board.HasMatingMaterial()) {
-      node->MakeTerminal(GameResult::DRAW);
+      node->MakeTerminal(GameResult::DRAW, search_->played_history_.GetLength());
       return;
     }
 
     if (history_.Last().GetNoCaptureNoPawnPly() >= 100) {
-      node->MakeTerminal(GameResult::DRAW);
+      node->MakeTerminal(GameResult::DRAW, search_->played_history_.GetLength());
       return;
     }
 
     if (history_.Last().GetRepetitions() >= 2) {
-      node->MakeTerminal(GameResult::DRAW);
+      node->MakeTerminal(GameResult::DRAW, search_->played_history_.GetLength());
       return;
     }
 
@@ -1005,11 +1004,11 @@ void SearchWorker::ExtendNode(Node* node) {
       if (state != FAIL) {
         // If the colors seem backwards, check the checkmate check above.
         if (wdl == WDL_WIN) {
-          node->MakeTerminal(GameResult::BLACK_WON);
+          node->MakeTerminal(GameResult::BLACK_WON, search_->played_history_.GetLength());
         } else if (wdl == WDL_LOSS) {
-          node->MakeTerminal(GameResult::WHITE_WON);
+          node->MakeTerminal(GameResult::WHITE_WON, search_->played_history_.GetLength());
         } else {  // Cursed wins and blessed losses count as draws.
-          node->MakeTerminal(GameResult::DRAW);
+          node->MakeTerminal(GameResult::DRAW, search_->played_history_.GetLength());
         }
         search_->tb_hits_.fetch_add(1, std::memory_order_acq_rel);
         return;