From 23baf72a4c95574d759a3fe6a5d1df2b0e92b223 Mon Sep 17 00:00:00 2001
From: Johannes Lenfers <j.lenfers@uni-muenster.de>
Date: Tue, 22 Oct 2024 17:51:30 +0200
Subject: [PATCH] catch empty rollout

---
 .../elevate/heuristic_search/heuristics/MCTS.scala  | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/main/scala/elevate/heuristic_search/heuristics/MCTS.scala b/src/main/scala/elevate/heuristic_search/heuristics/MCTS.scala
index 745448c1..93f04200 100644
--- a/src/main/scala/elevate/heuristic_search/heuristics/MCTS.scala
+++ b/src/main/scala/elevate/heuristic_search/heuristics/MCTS.scala
@@ -102,11 +102,16 @@ class MCTS[P] extends Heuristic[P] {
           // rollout performance should be the minimum that was seen during rollout
           rollout = choose_valid_solution_randomly(panel = panel, actions = actions, rollout._2)
 
-          rollout._1.solutionSteps.foreach(step => println(s"""[${step.strategy}, ${step.location}]"""))
-
-          // check if we have a dead end for this rollout
-          if (rollout._1 == null) {
+          // check if rollout is empty
+          if (rollout == null) {
             isTerminal = true
+          } else {
+            rollout._1.solutionSteps.foreach(step => println(s"""[${step.strategy}, ${step.location}]"""))
+
+            // check if we have a dead end for this rollout
+            if (rollout._1 == null) {
+              isTerminal = true
+            }
           }
 
         } else {