Fix a massive performance bug in A* and Dijkstra algorithms (10-100 t…

…imes faster now).
renggli · Dec 17, 2023 · e8808eb · e8808eb
1 parent f59f888
commit e8808eb
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Showing 2 changed files with 4 additions and 4 deletions.
diff --git a/lib/src/graph/algorithms/a_star_search.dart b/lib/src/graph/algorithms/a_star_search.dart
@@ -46,7 +46,7 @@ class _AStarSearchIterator<V> implements Iterator<Path<V, num>> {
 
   final AStarSearchIterable<V> iterable;
   final Map<V, _State<V>> states;
-  final PriorityQueue<_State<V>> todo = PriorityQueue();
+  final todo = PriorityQueue<_State<V>>();
 
   @override
   late Path<V, num> current;
@@ -61,11 +61,11 @@ class _AStarSearchIterator<V> implements Iterator<Path<V, num>> {
         final targetState = states.putIfAbsent(
             target, () => _State<V>(vertex: target, total: double.infinity));
         if (total < targetState.total) {
+          if (targetState.total.isFinite) todo.remove(targetState);
           targetState.parent = sourceState;
           targetState.value = value;
           targetState.total = total;
           targetState.estimate = total + iterable.costEstimate(target);
-          todo.remove(targetState);
           todo.add(targetState);
         }
       }

diff --git a/lib/src/graph/algorithms/dijkstra_search.dart b/lib/src/graph/algorithms/dijkstra_search.dart
@@ -41,7 +41,7 @@ class _DijkstraSearchIterator<V> implements Iterator<Path<V, num>> {
 
   final DijkstraSearchIterable<V> iterable;
   final Map<V, _State<V>> states;
-  final PriorityQueue<_State<V>> todo = PriorityQueue();
+  final todo = PriorityQueue<_State<V>>();
 
   @override
   late Path<V, num> current;
@@ -56,10 +56,10 @@ class _DijkstraSearchIterator<V> implements Iterator<Path<V, num>> {
         final targetState = states.putIfAbsent(
             target, () => _State<V>(vertex: target, total: double.infinity));
         if (total < targetState.total) {
+          if (targetState.total.isFinite) todo.remove(targetState);
           targetState.parent = sourceState;
           targetState.value = value;
           targetState.total = total;
-          todo.remove(targetState);
           todo.add(targetState);
         }
       }