update

src/mcts.jl

@@ -182,6 +182,7 @@ function simulate(a, node::MCTSNode, decisionMaker::Function, progressValueEstim
   
   for depth in 1:maxDepth
     if node.isterminal
+      simTrajectoryReward += node.reward
       break
     else
       simTrajectoryReward += node.reward
@@ -448,12 +449,15 @@ function runMCTS(
     while !isleaf(node)
       node = UCTselect(node, w)
     end
-
-    expand(a, node, decisionMaker, progressValueEstimator, isterminal, n=n)
-    
-    leafNode = UCTselect(node, w)
-    simTrajectoryReward = simulate(a, leafNode, decisionMaker, progressValueEstimator,
-                                  isterminal, maxDepth, n=n)
+    if node.isterminal
+      # MCTS arrive at the leaf node that is also a terminal state,
+      # do nothing then go directly to backpropagation
+    else
+      expand(a, node, decisionMaker, progressValueEstimator, isterminal, n=n)
+      leafNode = UCTselect(node, w)
+      simTrajectoryReward = simulate(a, leafNode, decisionMaker, progressValueEstimator,
+                                    isterminal, maxDepth, n=n)
+    end
     backpropagate(leafNode, simTrajectoryReward)
   end