Update the snap function using KDTree

Author: syhwawa

src/pam/operations/snap.py

@@ -3,10 +3,12 @@
 from pathlib import Path
 
 import geopandas as gp
+import numpy as np
 
 from pam.core import Population
 from pam.read import read_matsim
 from pam.write import write_matsim
+from scipy.spatial import cKDTree
 
 
 def snap_facilities_to_network(
@@ -19,11 +21,29 @@ def snap_facilities_to_network(
         network (gp.GeoDataFrame): A network geometry shapefile.
         link_id_field (str, optional): The link ID field to use in the network shapefile. Defaults to "id".
     """
-    link_ids = network[link_id_field]
+    if network.geometry.geom_type[0] == 'Point':
+        coordinates = np.array(list(zip(network.geometry.x, network.geometry.y)))
+    else:
+        coordinates = np.array(list(zip(network.geometry.centroid.x, network.geometry.centroid.y)))
+
+    tree = cKDTree(coordinates)
+    link_ids = network[link_id_field].values
+
+    activity_points = []
+    activities_info = []
     for _, _, person in population.people():
         for act in person.activities:
-            link_id = link_ids[network.distance(act.location.loc).argmin()]
-            act.location.link = link_id
+            point = act.location.loc
+            if not hasattr(point, 'x') or not hasattr(point, 'y'):
+                point = point.centroid
+            activity_points.append((point.x, point.y))
+            activities_info.append(act)
+
+    activity_points = np.array(activity_points)
+    distances, indices = tree.query(activity_points)
+
+    for act, index in zip(activities_info, indices):
+        act.location.link = link_ids[index]
 
 
 def run_facility_link_snapping(