Merge pull request #74 from PraneethJain/bidirectional

Added bi-directional Best First and Dijkstra

Author: brean

pathfinding/finder/__init__.py

@@ -1,2 +1,3 @@
 __all__ = ['a_star', 'best_first', 'bi_a_star', 'bi_breadth_first',
-           'breadth_first', 'dijkstra', 'finder', 'ida_star']
+           'bi_best_first', 'bi_dijkstra', 'breadth_first', 'dijkstra',
+           'finder', 'ida_star']

pathfinding/finder/bi_best_first.py

@@ -0,0 +1,46 @@
+from .bi_a_star import BiAStarFinder
+from ..core.diagonal_movement import DiagonalMovement
+from .finder import TIME_LIMIT, MAX_RUNS
+
+
+class BiBestFirstFinder(BiAStarFinder):
+    """
+    Bi-directional Best-First-Search algorithm.
+    It is essentially the same as bi-directional A* but with a high weight
+    on the heuristic, making it a greedy search.
+    """
+
+    def __init__(
+        self,
+        heuristic=None,
+        weight=1,
+        diagonal_movement=DiagonalMovement.never,
+        time_limit=TIME_LIMIT,
+        max_runs=MAX_RUNS,
+    ):
+        """
+        :param heuristic: heuristic used to calculate distance of 2 points
+            (defaults to manhattan)
+        :param weight: weight for the edges
+        :param diagonal_movement: if diagonal movement is allowed
+            (see enum in diagonal_movement)
+        :param time_limit: max. runtime in seconds
+        :param max_runs: max. amount of tries until we abort the search
+        """
+        super(BiBestFirstFinder, self).__init__(
+            heuristic=heuristic,
+            weight=weight,
+            diagonal_movement=diagonal_movement,
+            time_limit=time_limit,
+            max_runs=max_runs,
+        )
+
+        self.weighted = False
+
+    def apply_heuristic(self, node_a, node_b, heuristic=None, graph=None):
+        return (
+            super(BiBestFirstFinder, self).apply_heuristic(
+                node_a, node_b, heuristic, graph=graph
+            )
+            * 1000000
+        )

pathfinding/finder/bi_dijkstra.py

@@ -0,0 +1,39 @@
+from .bi_a_star import BiAStarFinder
+from ..core.diagonal_movement import DiagonalMovement
+from .finder import TIME_LIMIT, MAX_RUNS
+from ..core.heuristic import null
+
+
+class BiDijkstraFinder(BiAStarFinder):
+    """
+    Bi-directional Dijkstra's algorithm.
+
+    It is similar to bi-directional A* but with a heuristic of zero.
+    This means the search expands purely based on the lowest cost from the
+    start and end points.
+    """
+
+    def __init__(
+        self,
+        weight=1,
+        diagonal_movement=DiagonalMovement.never,
+        time_limit=TIME_LIMIT,
+        max_runs=MAX_RUNS,
+    ):
+        """
+        :param weight: weight for the edges
+        :param diagonal_movement: if diagonal movement is allowed
+            (see enum in diagonal_movement)
+        :param time_limit: max. runtime in seconds
+        :param max_runs: max. amount of tries until we abort the search
+        """
+        super(BiDijkstraFinder, self).__init__(
+            heuristic=null,
+            weight=weight,
+            diagonal_movement=diagonal_movement,
+            time_limit=time_limit,
+            max_runs=max_runs,
+        )
+
+    def apply_heuristic(self, node_a, node_b, heuristic=None, graph=None):
+        return 0

test/test_path.py

@@ -6,13 +6,15 @@
 from pathfinding.finder.a_star import AStarFinder
 from pathfinding.finder.best_first import BestFirst
 from pathfinding.finder.bi_a_star import BiAStarFinder
+from pathfinding.finder.bi_breadth_first import BiBreadthFirstFinder
+from pathfinding.finder.bi_best_first import BiBestFirstFinder
+from pathfinding.finder.bi_dijkstra import BiDijkstraFinder
 from pathfinding.finder.breadth_first import BreadthFirstFinder
 from pathfinding.finder.dijkstra import DijkstraFinder
 from pathfinding.finder.finder import ExecutionRunsException
 from pathfinding.finder.finder import ExecutionTimeException
 from pathfinding.finder.ida_star import IDAStarFinder
 from pathfinding.finder.msp import MinimumSpanningTree
-from pathfinding.finder.bi_breadth_first import BiBreadthFirstFinder
 
 import pytest
 
@@ -22,8 +24,9 @@
 # test scenarios from Pathfinding.JS
 scenarios = os.path.join(BASE_PATH, 'path_test_scenarios.json')
 data = json.load(open(scenarios, 'r', encoding='utf-8'))
-finders = [AStarFinder, BestFirst, BiAStarFinder, BiBreadthFirstFinder,
-           DijkstraFinder, IDAStarFinder, BreadthFirstFinder, MinimumSpanningTree]
+finders = [AStarFinder, BestFirst, BiAStarFinder, BiBreadthFirstFinder, 
+           BiBestFirstFinder, BiDijkstraFinder, DijkstraFinder, IDAStarFinder,
+           BreadthFirstFinder, MinimumSpanningTree]
 TIME_LIMIT = 10  # give it a 10 second limit.