removed remove_node

Author: peterchenadded

pathfinding/core/heap.py

@@ -1,19 +1,18 @@
 """Simple heap with ordering and removal."""
 import heapq
+from typing import Optional
 from .graph import Graph
 from .grid import Grid
 from .world import World
+from .node import Node
 
 
 class SimpleHeap:
-    """Simple wrapper around open_list that keeps track of order and removed
-    nodes automatically."""
+    """Simple wrapper around open_list that keeps track of order."""
 
     def __init__(self, node, grid):
         self.grid = grid
         self.open_list = [self._get_node_tuple(node, 0)]
-        self.removed_node_tuples = set()
-        self.heap_order = {}
         self.number_pushed = 0
 
     def _get_node_tuple(self, node, heap_order):
@@ -34,28 +33,27 @@ def _get_node_id(self, node):
         elif isinstance(self.grid, World):
             return (node.x, node.y, node.grid_id)
 
-    def pop_node(self):
-        """
-        Pops node off the heap. i.e. returns the one with the lowest f.
-
-        Notes:
-        1. Checks if that values is in removed_node_tuples first, if not tries
-           again.
-        2. We use this approach to avoid invalidating the heap structure.
-        """
-        node_tuple = heapq.heappop(self.open_list)
-        while node_tuple in self.removed_node_tuples:
+    def pop_node(self) -> Optional[Node]:
+        """Pops node off the heap. i.e. returns the one with the lowest f."""
+        while self.open_list:
             node_tuple = heapq.heappop(self.open_list)
 
-        if isinstance(self.grid, Graph):
-            node = self.grid.node(node_tuple[2])
-        elif isinstance(self.grid, Grid):
-            node = self.grid.node(node_tuple[2], node_tuple[3])
-        elif isinstance(self.grid, World):
-            node = self.grid.grids[
-                node_tuple[4]].node(node_tuple[2], node_tuple[3])
-
-        return node
+            if isinstance(self.grid, Graph):
+                node = self.grid.node(node_tuple[2])
+            elif isinstance(self.grid, Grid):
+                node = self.grid.node(node_tuple[2], node_tuple[3])
+            elif isinstance(self.grid, World):
+                node = self.grid.grids[
+                    node_tuple[4]].node(node_tuple[2], node_tuple[3])
+            
+            # node already updated with lower f, ignore
+            f = node_tuple[0]
+            if f > node.f:
+                continue
+            else:
+                return node
+
+        return None
 
     def push_node(self, node):
         """
@@ -65,27 +63,9 @@ def push_node(self, node):
         """
         self.number_pushed = self.number_pushed + 1
         node_tuple = self._get_node_tuple(node, self.number_pushed)
-        node_id = self._get_node_id(node)
-
-        self.heap_order[node_id] = self.number_pushed
 
         heapq.heappush(self.open_list, node_tuple)
 
-    def remove_node(self, node, f):
-        """
-        Remove the node from the heap.
-
-        This just stores it in a set and we just ignore the node if it does
-        get popped from the heap.
-
-        :param node: The node to remove.
-        :param f: The old f value of the node.
-        """
-        node_id = self._get_node_id(node)
-        heap_order = self.heap_order[node_id]
-        node_tuple = self._get_node_tuple(node, heap_order)
-        self.removed_node_tuples.add(node_tuple)
-
     def __len__(self):
         """Returns the length of the open_list."""
         return len(self.open_list)

pathfinding/finder/finder.py

@@ -131,7 +131,6 @@ def process_node(
         ng = parent.g + graph.calc_cost(parent, node, self.weighted)
 
         if not node.opened or ng < node.g:
-            old_f = node.f
             node.g = ng
             node.h = node.h or self.apply_heuristic(node, end, graph=graph)
             # f is the estimated total cost from start to goal
@@ -144,7 +143,6 @@ def process_node(
                 # the node can be reached with smaller cost.
                 # Since its f value has been updated, we have to
                 # update its position in the open list
-                open_list.remove_node(node, old_f)
                 open_list.push_node(node)
 
     def check_neighbors(self, start, end, graph, open_list,

pytest.ini

@@ -1,4 +1,5 @@
 [pytest]
+pythonpath = .
 log_cli = 1
 log_cli_level = INFO
 log_cli_format = %(asctime)s.%(msecs)03d [%(levelname)8s] (%(filename)s:%(lineno)s) %(message)s

test/test_heap.py

@@ -16,11 +16,17 @@ def test_heap():
     open_list.push_node(grid.node(1, 2))
     open_list.push_node(grid.node(1, 3))
 
-    # Test removal and pop
-    assert len(open_list) == 3
-    open_list.remove_node(grid.node(1, 2), 0)
-    assert len(open_list) == 3
-
     assert open_list.pop_node() == grid.node(1, 1)
+    assert open_list.pop_node() == grid.node(1, 2)
     assert open_list.pop_node() == grid.node(1, 3)
     assert len(open_list) == 0
+
+    # Test inconsistent f
+    test_node = grid.node(1,1)
+    test_node.f = 1
+    open_list.push_node(test_node)
+    test_node.f = 0
+    open_list.push_node(test_node)
+    assert open_list.pop_node() == test_node
+    assert open_list.pop_node() is None
+    assert len(open_list) == 0