Strangely enough, but I cannot repeat the bugs.

Author: coderodde

src/main/java/io/github/coderodde/pathfinding/app/SettingsPane.java

@@ -400,7 +400,7 @@ protected List<Cell> call() throws Exception {
                                                     this.path,
                                                     pathfindingSettings));
                     }
-                });
+                }); 
 
                 new Thread(task).start();
 

src/main/java/io/github/coderodde/pathfinding/finders/BeamStackSearchFinder.java

@@ -79,7 +79,7 @@ public List<Cell> findPath(GridModel model,
 
             while (!beamStack.isEmpty() && beamStack.peek().fmax >= U.value) {
                 beamStack.pop();
-            }
+            }   
 
             if (beamStack.isEmpty()) {
                 return optimalPath == null ? List.of() : optimalPath;
@@ -316,9 +316,8 @@ private static void pruneLayer(GridModel model,
 
         for (HeapNode heapNode : pruneList) {
             open.remove(heapNode);
-            
             Cell cell = heapNode.cell;
-            
+
             if (!cell.getCellType().equals(CellType.SOURCE) &&
                 !cell.getCellType().equals(CellType.TARGET)) {
                 model.setCellType(cell, CellType.VISITED);

src/main/java/io/github/coderodde/pathfinding/logic/PathfindingSettings.java

@@ -111,6 +111,7 @@ public int getBeamWidth() {
     }
 
     public void setBeamWidth(int beamWidth) {
+        System.out.println("Setting beam width " + beamWidth);
         if (beamWidth < 1) {
             throw new IllegalArgumentException(
                     String.format("beamWidth(%d) < 1", beamWidth));

src/main/java/io/github/coderodde/pathfinding/logic/SearchStatistics.java

@@ -44,10 +44,21 @@ public SearchStatistics(Label labelVisited,
         this.labelRejected = labelRejected;
         this.labelSelectors.addAll(Arrays.asList(selectors));
 
-        this.labelVisited .setText("Visited: N/A");
-        this.labelOpened  .setText("Opened: N/A");
-        this.labelTraced  .setText("Traced: N/A");
-        this.labelRejected.setText("Rejected: N/A");
+        if (labelVisited != null) {
+            this.labelVisited .setText("Visited: N/A");
+        }
+            
+        if (labelOpened != null) {
+            this.labelOpened  .setText("Opened: N/A");
+        }
+            
+        if (labelTraced != null) {
+            this.labelTraced  .setText("Traced: N/A");
+        }
+            
+        if (labelRejected != null) {
+            this.labelRejected.setText("Rejected: N/A");
+        }
     }
 
     public void incrementVisited() {
@@ -65,6 +76,10 @@ public void decrementOpened() {
     public void incrementTraced() {
         traced++;
 
+        if (labelTraced == null) {
+            return;
+        }
+        
         Platform.runLater(() -> {
             if (labelSelectors.contains(LabelSelector.TRACED)) {
                 labelTraced.setText(String.format("Traced: %d", traced));
@@ -77,6 +92,10 @@ public void incrementTraced() {
     public void incrementRejected() {
         rejected++;
 
+        if (labelRejected == null) {
+            return;
+        }
+        
         Platform.runLater(() -> {
             if (labelSelectors.contains(LabelSelector.REJECTED)) {
                 labelRejected.setText(String.format("Rejected: %d", rejected));
@@ -89,6 +108,10 @@ public void incrementRejected() {
     public void addToOpened(int delta) {
         opened += delta;
 
+        if (labelOpened == null) {
+            return;
+        }
+        
         Platform.runLater(() -> {
             if (labelSelectors.contains(LabelSelector.OPENED)) {
                 labelOpened.setText(String.format("Opened: %d", opened));
@@ -101,6 +124,10 @@ public void addToOpened(int delta) {
     public void addToVisited(int delta) {
         visited += delta;
 
+        if (labelVisited == null) {
+            return;
+        }
+        
         Platform.runLater(() -> {
             if (labelSelectors.contains(LabelSelector.VISITED)) {
                 labelVisited.setText(String.format("Visited: %d", visited));

src/test/java/io/github/coderodde/pathfinding/finders/BeamStackSearchFinderTest.java

@@ -0,0 +1,113 @@
+package io.github.coderodde.pathfinding.finders;
+
+import io.github.coderodde.pathfinding.heuristics.OctileHeuristicFunction;
+import io.github.coderodde.pathfinding.logic.GridCellNeighbourIterable;
+import io.github.coderodde.pathfinding.logic.GridNodeExpander;
+import io.github.coderodde.pathfinding.logic.PathfindingSettings;
+import io.github.coderodde.pathfinding.logic.SearchState;
+import io.github.coderodde.pathfinding.logic.SearchStatistics;
+import io.github.coderodde.pathfinding.model.GridModel;
+import io.github.coderodde.pathfinding.utils.Cell;
+import io.github.coderodde.pathfinding.utils.CellType;
+import java.util.List;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class BeamStackSearchFinderTest {
+    
+    private final PathfindingSettings ps = new PathfindingSettings();
+    private final SearchState searchState = new SearchState();
+    private final SearchStatistics searchStatistics =
+            new SearchStatistics(null, 
+                                 null,
+                                 null,
+                                 null);
+    
+    public BeamStackSearchFinderTest() {
+        ps.setDontCrossCorners(true);
+        ps.setFinder(new BeamStackSearchFinder());
+        ps.setHeuristicFunction(new OctileHeuristicFunction());
+        ps.setFrequency(1000);
+    }
+    
+    @Test
+    public void hasSolutionPath() {
+        GridModel model = new GridModel(20, 5);
+        model.moveTarget(17, 2);
+        model.moveSource(15, 2);
+        model.setCellType(16, 2, CellType.WALL);
+        ps.setBeamWidth(1);
+        
+        GridNodeExpander expander = new GridNodeExpander(model, ps);
+        
+        GridCellNeighbourIterable iterable =
+                new GridCellNeighbourIterable(model, 
+                                              expander,
+                                              ps);
+        
+        List<Cell> pathBreadthFirstSearch = 
+                new BFSFinder()
+                        .findPath(model, 
+                                  iterable, 
+                                  ps,
+                                  searchState, 
+                                  searchStatistics);
+        
+        List<Cell> pathBeamStackSearch = 
+                new BeamStackSearchFinder()
+                        .findPath(model, 
+                                  iterable, 
+                                  ps,
+                                  searchState, 
+                                  searchStatistics);
+        
+        System.out.println("BSS: " + pathBeamStackSearch.size());
+        System.out.println("BFS: " + pathBreadthFirstSearch.size());
+        
+        assertEquals(pathBreadthFirstSearch.size(),
+                     pathBeamStackSearch.size());
+    }
+    
+    @Test
+    public void debugNoPath() {
+        GridModel model = new GridModel(53, 33);
+        model.moveTarget(6, 4);
+        model.moveSource(3, 4);
+        model.setCellType(4, 2, CellType.WALL);
+        model.setCellType(4, 3, CellType.WALL);
+        model.setCellType(5, 3, CellType.WALL);
+        model.setCellType(5, 4, CellType.WALL);
+        model.setCellType(5, 5, CellType.WALL);
+        
+        ps.setBeamWidth(1);
+        
+        GridNodeExpander expander = new GridNodeExpander(model, ps);
+        
+        GridCellNeighbourIterable iterable =
+                new GridCellNeighbourIterable(model, 
+                                              expander,
+                                              ps);
+        
+        List<Cell> pathBreadthFirstSearch = 
+                new BFSFinder()
+                        .findPath(model, 
+                                  iterable, 
+                                  ps,
+                                  searchState, 
+                                  searchStatistics);
+        
+        List<Cell> pathBeamStackSearch = 
+                new BeamStackSearchFinder()
+                        .findPath(model, 
+                                  iterable, 
+                                  ps,
+                                  searchState, 
+                                  searchStatistics);
+        
+        System.out.println("BSS: " + pathBeamStackSearch.size());
+        System.out.println("BFS: " + pathBreadthFirstSearch.size());
+        
+        assertEquals(pathBreadthFirstSearch.size(),
+                     pathBeamStackSearch.size());
+    }
+}