Resolved merge conflict.

Author: coderodde

src/main/java/com/github/coderodde/graph/pathfinding/delayed/impl/ThreadPoolBidirectionalBFSPathFinder.java

@@ -843,9 +843,7 @@ private void tryUpdateIfImprovementPossible(
                 parents.put(node, predecessor);
 
                 if (heap.containsDatum(node)) {
-                    heap.updatePriority(node, updatedDistance);   
-                } else {
-                    heap.insert(node, updatedDistance);
+                    heap.updatePriority(node, updatedDistance);
                 }
             }
         }
@@ -1117,7 +1115,10 @@ private void processCurrentInMasterThread() {
 
             for (int trials = 0; trials < threadSleepTrials; trials++) {
                 mysleep(threadSleepDurationNanos);
+                
+                lock();
                 currentHead = searchState.heap.minimumNode();
+                unlock();
 
                 if (currentHead != null) {
                     break;

src/test/java/com/github/coderodde/graph/pathfinding/delayed/impl/ThreadPoolBidirectionalBFSPathFinderTest.java

@@ -17,7 +17,7 @@
 public final class ThreadPoolBidirectionalBFSPathFinderTest {
 
     private static final long SEED = 13L;
-    private static final int NODES = 50_000;
+    private static final int NODES = 100_000;
     private static final int DISCONNECTED_GRAPH_NODES = 1000;
     private static final int MINIMUM_DISCONNECTED_GRAPH_DEGREE = 2;
     private static final int MAXIMUM_DISCONNECTED_GRAPH_DEGREE = 5;