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Write instances and solutions (#109)
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‎README.md

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[![codecov](https://codecov.io/gh/leonlan/VRPLIB/branch/master/graph/badge.svg?token=X0X66LBNZ7)](https://codecov.io/gh/leonlan/VRPLIB)
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`vrplib` is a Python package for working with Vehicle Routing Problem (VRP) instances. The main features are:
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- reading VRPLIB and Solomon instances and solutions, and
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- reading VRPLIB and Solomon instances and solutions,
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- writing VRPLIB-style instances and solutions, and
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- downloading instances and best known solutions from [CVRPLIB](http://vrp.atd-lab.inf.puc-rio.br/index.php/en/).
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## Outline
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- [Installation](#installation)
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- [Example usage](#example-usage)
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- [Documentation](#documentation)
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## Installation
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`vrplib` works with Python 3.8+ and only depends on `numpy`.
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`vrplib` works with Python 3.8+ and only depends on `numpy`. It may be installed in the usual way as
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```shell
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pip install vrplib
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```
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## Example usage
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### Reading instances and solutions
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### Reading files
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```python
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import vrplib
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```
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### Downloading instances from CVRPLIB
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### Writing files
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The functions `write_instance` and `write_solution` provide a simple interface to writing instances and solutions in VRPLIB-style:
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- `write_instance` adds indices to data sections when necessary (`EDGE_WEIGHT_SECTION` and `DEPOT_SECTION` are excluded).
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- `write_solution` adds the `Route #{idx}` prefix to routes.
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Note that these functions do not validate instances: it is up to the user to write correct VRPLIB-style files.
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#### Instances
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``` python
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import vrplib
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instance_loc = "instance.vrp"
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instance_data = {
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"NAME": "instance",
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"TYPE": "CVRP",
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"VEHICLES": 2,
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"DIMENSION": 1,
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"CAPACITY": 1,
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"EDGE_WEIGHT_TYPE": "EUC_2D",
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"NODE_COORD_SECTION": [[250, 250], [500, 500]],
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"DEMAND_SECTION": [1, 1],
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"DEPOT_SECTION": [1],
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}
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vrplib.write_instance(instance_loc, instance_data)
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```
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```
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NAME: instance
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TYPE: CVRP
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VEHICLES: 2
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DIMENSION: 1
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CAPACITY: 1
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EDGE_WEIGHT_TYPE: EUC_2D
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NODE_COORD_SECTION
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1 250 250
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2 500 500
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DEMAND_SECTION
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1 1
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2 1
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DEPOT_SECTION
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1
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EOF
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```
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#### Solutions
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``` python
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import vrplib
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solution_loc = "solution.sol"
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routes = [[1], [2, 3], [4, 5, 6]]
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solution_data = {"Cost": 42, "Vehicle types": [1, 2, 3]}
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vrplib.write_solution(solution_loc, routes, solution_data)
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```
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``` { .html }
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Route #1: 1
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Route #2: 2 3
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Route #3: 4 5 6
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Cost: 42
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Vehicle types: [1, 2, 3]
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```
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### Downloading from CVRPLIB
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``` python
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import vrplib
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‎tests/write/__init__.py

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‎tests/write/test_write_instance.py

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import numpy as np
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from numpy.testing import assert_equal
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from pytest import mark
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from vrplib import write_instance
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@mark.parametrize(
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"key, value, desired",
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(
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["name", "Instance", "name: Instance"], # string
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["DIMENSION", 100, "DIMENSION: 100"], # int
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["VEHICLES", -10, "VEHICLES: -10"], # negative
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["CAPACITY", 10.5, "CAPACITY: 10.5"], # float
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["EMPTY", "", "EMPTY: "], # empty
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),
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)
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def test_specifications(tmp_path, key, value, desired):
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"""
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Tests that key-value pairs where values are floats or strings are
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formatted as specifications.
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"""
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name = "specifications"
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instance = {key: value}
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write_instance(tmp_path / name, instance)
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desired = "\n".join([desired, "EOF", ""])
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), desired)
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@mark.parametrize(
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"key, value, desired",
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(
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# 1-dimensional list
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["X_SECTION", [0, 10], "\n".join(["X_SECTION", "1\t0", "2\t10"])],
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# 1-dimensional list with mixed int and float values
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["X_SECTION", [0, 10.5], "\n".join(["X_SECTION", "1\t0", "2\t10.5"])],
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# 1-dimensional list empty
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["X_SECTION", [], "\n".join(["X_SECTION"])],
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# 2-dimensional numpy array
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[
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"Y_SECTION",
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np.array([[0, 0], [1, 1]]),
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"\n".join(["Y_SECTION", "1\t0\t0", "2\t1\t1"]),
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],
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# 2-dimensional list empty
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["Y_SECTION", [[]], "\n".join(["Y_SECTION", "1\t"])],
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# 2-dimensional array with different row lengths
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# NOTE: This is currently an invalid VRPLIB format, see
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# https://github.com/leonlan/VRPLIB/issues/108.
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[
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"DATA_SECTION",
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[[1], [3, 4]],
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"\n".join(["DATA_SECTION", "1\t1", "2\t3\t4"]),
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],
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),
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)
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def test_sections(tmp_path, key, value, desired):
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"""
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Tests that key-value pairs where values are lists are formatted as
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sections.
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"""
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name = "sections"
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instance = {key: value}
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write_instance(tmp_path / name, instance)
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), "\n".join([desired, "EOF", ""]))
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def test_no_indices_depot_and_edge_weight_section(tmp_path):
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"""
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Tests that indices are not included when formatting depot and edge weight
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section.
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"""
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# Let's first test the depot section.
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name = "depot"
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instance = {"DEPOT_SECTION": [1, 2]}
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write_instance(tmp_path / name, instance)
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desired = "\n".join(["DEPOT_SECTION", "1", "2", "EOF", ""])
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), desired)
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# Now let's test the edge weight section.
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name = "edge_weight"
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instance = {
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"EDGE_WEIGHT_SECTION": [
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[1, 1, 2],
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[1, 0, 3],
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[1, 3, 0],
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]
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}
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write_instance(tmp_path / name, instance)
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desired = "\n".join(
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[
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"EDGE_WEIGHT_SECTION",
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"1\t1\t2",
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"1\t0\t3",
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"1\t3\t0",
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"EOF",
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"",
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]
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)
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), desired)
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def test_small_instance_example(tmp_path):
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"""
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Tests if writing a small instance yields the correct result.
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"""
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name = "C101"
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instance = {
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"NAME": name,
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"TYPE": "VRPTW",
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"DIMENSION": 4,
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"CAPACITY": 200,
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"NODE_COORD_SECTION": [
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[40, 50],
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[45, 68],
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[45, 70],
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[42, 66],
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],
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"DEMAND_SECTION": [0, 10, 30, 10],
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"DEPOT_SECTION": [1],
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}
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write_instance(tmp_path / name, instance)
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desired = "\n".join(
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[
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"NAME: C101",
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"TYPE: VRPTW",
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"DIMENSION: 4",
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"CAPACITY: 200",
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"NODE_COORD_SECTION",
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"1\t40\t50",
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"2\t45\t68",
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"3\t45\t70",
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"4\t42\t66",
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"DEMAND_SECTION",
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"1\t0",
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"2\t10",
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"3\t30",
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"4\t10",
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"DEPOT_SECTION",
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"1",
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"EOF",
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"",
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]
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)
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), desired)

‎tests/write/test_write_solution.py

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from numpy.testing import assert_equal, assert_raises
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from pytest import mark
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from vrplib import write_solution
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@mark.parametrize(
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"routes, desired",
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[
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([[1, 2]], "Route #1: 1 2"),
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([[1, 2], [42, 9]], "Route #1: 1 2\nRoute #2: 42 9"),
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],
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)
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def test_write_routes(tmp_path, routes, desired):
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"""
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Tests the writing of a solution with routes.
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"""
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name = "test.sol"
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write_solution(tmp_path / name, routes)
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), desired + "\n")
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def test_raise_empty_routes(tmp_path):
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"""
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Tests that an error is raised if a route is empty.
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"""
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name = "test.sol"
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with assert_raises(ValueError):
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write_solution(tmp_path / name, [[]])
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with assert_raises(ValueError):
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write_solution(tmp_path / name, [[1], []])
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@mark.parametrize(
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"data, desired",
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[
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({"Cost": 100}, "Cost: 100"), # int
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({"Time": 123.45}, "Time: 123.45"), # float
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({"Distance": -1}, "Distance: -1"), # negative int
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({"name": "test.sol"}, "name: test.sol"), # string
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({"Vehicle types": [1, 2, 3]}, "Vehicle types: [1, 2, 3]"), # list
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({"Vehicle types": (1, 3)}, "Vehicle types: (1, 3)"), # tuple
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],
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)
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def test_format_other_data(tmp_path, data, desired):
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name = "test.sol"
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routes = [[1]]
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write_solution(tmp_path / name, routes, data)
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with open(tmp_path / name, "r") as fh:
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text = "Route #1: 1" + "\n" + desired + "\n"
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assert_equal(fh.read(), text)
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def test_small_example(tmp_path):
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"""
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Tests the writing of a small example.
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"""
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name = "test.sol"
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routes = [[1, 2], [3, 4], [5]]
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data = {"Cost": 100, "Time": 123.45, "name": name}
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write_solution(tmp_path / name, routes, data)
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desired = "\n".join(
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[
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"Route #1: 1 2",
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"Route #2: 3 4",
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"Route #3: 5",
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"Cost: 100",
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"Time: 123.45",
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"name: test.sol",
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"",
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]
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)
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with open(tmp_path / name, "r") as fh:
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assert_equal(fh.read(), desired)

‎vrplib/__init__.py

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from .download import download_instance, download_solution, list_names
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from .read import read_instance, read_solution
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from .write import write_instance, write_solution

‎vrplib/write/__init__.py

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from .write_instance import write_instance
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from .write_solution import write_solution

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