81 lines
2.4 KiB
Python
81 lines
2.4 KiB
Python
import time
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from itertools import permutations
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from typing import Tuple
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import numpy as np
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import numpy.typing as npt
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from common import plot_plan, read_data
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def exhaustive_search(distances: npt.NDArray) -> Tuple[float, npt.NDArray]:
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"""An implementation of exhaustive search.
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This implementation takes a permutation iterator, then maps each
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element to a tuple containing the travel distance of that permutation
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and the permutation tuple itself. Finally the function returns the
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tuple that contains the smallest travel distance.
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Args:
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distances (npt.NDArray): An array containing distances to travel.
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Returns:
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A tuple containing the shortest travel distance and its corresponding
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permutation.
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"""
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size = len(distances)
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return min( # Find the smallest travel distance from the array
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map( # Map the permutation array to contain tuples (distance, permutation)
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lambda perm: (
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sum([distances[perm[i - 1], perm[i]] for i in range(size)]),
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np.array(perm)
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),
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permutations(range(size)),
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),
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)
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if __name__ == "__main__":
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cities, data = read_data("./european_cities.csv")
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# A loop timing finding the optimal solution for different n
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for n in range(6, 11):
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# Time exhaustive search
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t0 = time.time_ns()
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distance, perm = exhaustive_search(data[:n, :n])
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t1 = time.time_ns()
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time_elapsed_ms = (t1 - t0) / 1_000_000.0
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print(f"Exhaustive search for the {n} first cities:")
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print(f"distance : {distance:>12.6f}km")
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print(f"time to find solution: {time_elapsed_ms:>12.6f}ms\n")
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"""Running example
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oblig1 on main [?] via 🐍 v3.12.6 took 7s
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❯ python exhaustive_search.py
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Exhaustive search for the 6 first cities:
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distance : 5018.810000km
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time to find solution: 1.105330ms
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Exhaustive search for the 7 first cities:
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distance : 5487.890000km
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time to find solution: 10.089604ms
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Exhaustive search for the 8 first cities:
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distance : 6667.490000km
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time to find solution: 78.810508ms
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Exhaustive search for the 9 first cities:
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distance : 6678.550000km
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time to find solution: 765.676230ms
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Exhaustive search for the 10 first cities:
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distance : 7486.310000km
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time to find solution: 8281.795515ms
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"""
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