Rewrite python routing layer to use pybind11; port samples

Author: lperron

ortools/constraint_solver/python/constraint_solver.cc

@@ -103,7 +103,8 @@ int main(int argc, char* argv[]) {
 """Vehicle Routing example."""
 
 from ortools.routing import enums_pb2
-from ortools.routing import pywraprouting
+from ortools.routing import parameters_pb2
+from ortools.routing.python import routing
 
 
 def main():
@@ -114,46 +115,50 @@ def main():
   depot = 0
 
   # Create the routing index manager.
-  manager = pywraprouting.IndexManager(
-      num_locations, num_vehicles, depot
-  )
+  manager = routing.IndexManager(num_locations, num_vehicles, depot)
 
-  # Create Routing Model.
-  routing = pywraprouting.Model(manager)
+  # Create Routing routing.
+  routing_model = routing.Model(manager)
 
   # Create and register a transit callback.
   def distance_callback(from_index, to_index):
     """Returns the absolute difference between the two nodes."""
     # Convert from routing variable Index to user NodeIndex.
-    from_node = int(manager.IndexToNode(from_index))
-    to_node = int(manager.IndexToNode(to_index))
+    from_node = int(manager.index_to_node(from_index))
+    to_node = int(manager.index_to_node(to_index))
     return abs(to_node - from_node)
 
-  transit_callback_index = routing.RegisterTransitCallback(distance_callback)
+  transit_callback_index = routing_model.register_transit_callback(
+      distance_callback
+  )
 
   # Define cost of each arc.
-  routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)
+  routing_model.set_arc_cost_evaluator_of_all_vehicles(transit_callback_index)
 
   # Setting first solution heuristic.
-  search_parameters = pywraprouting.DefaultRoutingSearchParameters()
+  search_parameters: parameters_pb2.RoutingSearchParameters = (
+      routing.default_routing_search_parameters()
+  )
   search_parameters.first_solution_strategy = (
       enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC
   )  # pylint: disable=no-member
 
   # Solve the problem.
-  assignment = routing.SolveWithParameters(search_parameters)
+  assignment = routing_model.solve_with_parameters(search_parameters)
 
   # Print solution on console.
-  print(f"Objective: {assignment.ObjectiveValue()}")
-  index = routing.Start(0)
+  print(f"Objective: {assignment.objective_value()}")
+  index = routing_model.start(0)
   plan_output = "Route for vehicle 0:\n"
   route_distance = 0
-  while not routing.IsEnd(index):
-    plan_output += f"{manager.IndexToNode(index)} -> "
+  while not routing_model.is_end(index):
+    plan_output += f"{manager.index_to_node(index)} -> "
     previous_index = index
-    index = assignment.Value(routing.NextVar(index))
-    route_distance += routing.GetArcCostForVehicle(previous_index, index, 0)
-  plan_output += f"{manager.IndexToNode(index)}\n"
+    index = assignment.value(routing_model.next_var(index))
+    route_distance += routing_model.get_arc_cost_for_vehicle(
+        previous_index, index, 0
+    )
+  plan_output += f"{manager.index_to_node(index)}\n"
   plan_output += f"Distance of the route: {route_distance}m\n"
   print(plan_output)
 

ortools/routing/docs/ROUTING.md

@@ -0,0 +1,63 @@
+# Copyright 2010-2025 Google LLC
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Description: python wrapping of the C++ code of the routing library.
+
+load("@pip_deps//:requirements.bzl", "requirement")
+load("@pybind11_bazel//:build_defs.bzl", "pybind_extension")
+load("@rules_cc//cc:cc_library.bzl", "cc_library")
+load("@rules_python//python:py_test.bzl", "py_test")
+
+cc_library(
+    name = "doc",
+    hdrs = [
+        "doc.h",
+        "index_manager_doc.h",
+        "parameters_doc.h",
+    ],
+)
+
+pybind_extension(
+    name = "routing",
+    srcs = ["routing.cc"],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":doc",
+        "//ortools/constraint_solver:cp",
+        "//ortools/constraint_solver:solver_parameters_cc_proto",
+        "//ortools/constraint_solver/python:constraint_solver",
+        "//ortools/routing",
+        "//ortools/routing:index_manager",
+        "//ortools/routing:parameters",
+        "//ortools/routing:types",
+        "//ortools/util:sorted_interval_list",
+        "//ortools/util/python:sorted_interval_list",
+        "@abseil-cpp//absl/algorithm:container",
+        "@abseil-cpp//absl/container:flat_hash_set",
+        "@pybind11_abseil//pybind11_abseil:absl_casters",
+        "@pybind11_protobuf//pybind11_protobuf:native_proto_caster",
+    ],
+)
+
+py_test(
+    name = "routing_test",
+    size = "small",
+    srcs = ["routing_test.py"],
+    deps = [
+        ":routing",
+        requirement("absl-py"),
+        "//ortools/constraint_solver/python:constraint_solver",
+        "//ortools/routing:enums_py_pb2",
+        "//ortools/routing:parameters_py_pb2",
+    ],
+)

ortools/routing/python/BUILD.bazel

@@ -12,9 +12,9 @@
 # limitations under the License.
 
 # routing
-pybind11_add_module(routing_pybind11 MODULE model.cc)
+pybind11_add_module(routing_pybind11 MODULE routing.cc)
 set_target_properties(routing_pybind11 PROPERTIES
-  LIBRARY_OUTPUT_NAME "model")
+  LIBRARY_OUTPUT_NAME "routing")
 
 # note: macOS is APPLE and also UNIX !
 if(APPLE)
@@ -29,6 +29,7 @@ endif()
 target_link_libraries(routing_pybind11 PRIVATE
   ${PROJECT_NAMESPACE}::ortools
   pybind11_native_proto_caster
+  pybind11_abseil::absl_casters
 )
 add_library(${PROJECT_NAMESPACE}::routing_pybind11 ALIAS routing_pybind11)