121 lines
4.1 KiB
Python
Executable File
121 lines
4.1 KiB
Python
Executable File
#!/usr/bin/env python3
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# Copyright 2010-2025 Google LLC
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# [START program]
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"""Sample to better understand Node/Index relation.
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This script generate few markdown tables to better understand
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the relation between nodes and indices.
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Things to notice:
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* Since we have two duplicates (node 5 and node 4) solver need 2 extra indices
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to have an unique index for each vehicle start/stop and locations.
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* Solver needs to "create" an index for a vehicle 1 start since solver need an
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unique start index per vehicle.
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* All end nodes are moved to the end of the index list aka [15, 16, 17, 18].
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* routing.Size() return the number of node which are not end nodes (here 15 aka
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[0-14])
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note: using the two properties above, we know that any index in
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range(routing.Size()) is not a vehicle end node.
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* Since end nodes are moved to the end, their respective "empty" node index are
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reused so all locations indices are "shifted"
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e.g. node 9 is mapped to index 6
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* Same for start nodes which are moved to "empty" space
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e.g. start node 7 mapped to index 4
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Takeaway:
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* Allways use routing.Start(), routing.End(), manager.IndexToNode() or
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manager.NodeToIndex().
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* Location node is not necessarily equal to its index.
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* To loop through ALL indices use manager.GetNumberOfIndices() (Python) or
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manager::num_indices() (C++)
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"""
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from ortools.constraint_solver import routing_enums_pb2
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from ortools.constraint_solver import pywrapcp
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def main():
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"""Entry point of the program."""
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locations = 17
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starts = [5, 5, 7, 8]
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ends = [1, 2, 4, 4]
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vehicles = len(starts)
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assert len(starts) == len(ends)
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manager = pywrapcp.RoutingIndexManager(locations, vehicles, starts, ends)
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routing = pywrapcp.RoutingModel(manager)
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print("Starts/Ends:")
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header = "| |"
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separator = "|---|"
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v_starts = "| start |"
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v_ends = "| end |"
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for v in range(manager.GetNumberOfVehicles()):
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header += f" vehicle {v} |"
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separator += "---|"
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v_starts += f" {starts[v]} |"
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v_ends += f" {ends[v]} |"
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print(header)
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print(separator)
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print(v_starts)
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print(v_ends)
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print("\nNodes:")
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print(
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"| locations | manager.GetNumberOfNodes | manager.GetNumberOfIndices |"
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" routing.nodes | routing.Size |"
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)
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print("|---|---|---|---|---|")
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print(
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f"| {locations} | {manager.GetNumberOfNodes()} |"
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f" {manager.GetNumberOfIndices()} | {routing.nodes()} |"
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f" {routing.Size()} |"
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)
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print("\nLocations:")
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print("| node | index | routing.IsStart | routing.IsEnd |")
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print("|---|---|---|---|")
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for node in range(manager.GetNumberOfNodes()):
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if node in starts or node in ends:
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continue
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index = manager.NodeToIndex(node)
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print(
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f"| {node} | {index} | {routing.IsStart(index)} |"
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f" {routing.IsEnd(index)} |"
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)
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print("\nStart/End:")
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print("| vehicle | Start/end | node | index | routing.IsStart | routing.IsEnd |")
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print("|---|---|---|---|---|---|")
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for v in range(manager.GetNumberOfVehicles()):
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start_index = routing.Start(v)
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start_node = manager.IndexToNode(start_index)
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print(
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f"| {v} | start | {start_node} | {start_index} |"
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f" {routing.IsStart(start_index)} | {routing.IsEnd(start_index)} |"
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)
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for v in range(manager.GetNumberOfVehicles()):
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end_index = routing.End(v)
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end_node = manager.IndexToNode(end_index)
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print(
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f"| {v} | end | {end_node} | {end_index} |"
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f" {routing.IsStart(end_index)} | {routing.IsEnd(end_index)} |"
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)
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if __name__ == "__main__":
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main()
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# [END program]
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