TSP heuristics

Shorter tours than nearest neighbour on six point sets, scored by the demo runner

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1	#!/usr/bin/env python3
2	"""Score a route's travelling-salesman heuristic on six fixed point sets: its tour's length over nearest neighbour's.
3
4	Usage: score.py ROUTE_FOLDER. The route's solve.py (or the baseline's, at the top of the project, if the route has
5	none) reads the points as JSON on stdin and prints the tour as JSON. It runs in its own process and only the tour it
6	prints is used. Writes metrics.json; the last line sums up."""
7	import json
8	import math
9	import random
10	import subprocess
11	import sys
12	import time
13	from pathlib import Path
14
15
16	def points(n, seed):
17	rng = random.Random(seed)
18	return [[round(rng.random(), 6), round(rng.random(), 6)] for _ in range(n)]
19
20
21	SETS = {f"n{n}-{s}": points(n, s) for n, s in [(40, 1), (40, 2), (80, 3), (80, 4), (160, 5), (160, 6)]}
22
23
24	def length(p, tour):
25	return sum(math.dist(p[tour[i - 1]], p[tour[i]]) for i in range(len(tour)))
26
27
28	def nearest(p):
29	left, tour = set(range(1, len(p))), [0]
30	while left:
31	nxt = min(left, key=lambda j: math.dist(p[tour[-1]], p[j]))
32	left.remove(nxt)
33	tour.append(nxt)
34	return tour
35
36
37	folder = Path(sys.argv[1])
38	solver = folder / "solve.py" if (folder / "solve.py").is_file() else Path("input/solve.py")
39	subtasks, seconds = {}, 0.0
40	for name, p in SETS.items():
41	start = time.perf_counter()
42	try:
43	out = subprocess.run([sys.executable, str(solver)], input=json.dumps(p), capture_output=True, text=True, timeout=30)
44	tour = json.loads(out.stdout)
45	ok = isinstance(tour, list) and sorted(tour) == list(range(len(p)))
46	except Exception as e:
47	print(f"{name}: the solver failed ({type(e).__name__})")
48	sys.exit(1)
49	seconds += time.perf_counter() - start
50	if not ok:
51	print(f"{name}: the tour must visit every point exactly once")
52	sys.exit(1)
53	subtasks[name] = round(length(p, tour) / length(p, nearest(p)), 4)
54	if seconds > 30:
55	print(f"took {seconds:.1f} s; the limit is 30 s")
56	sys.exit(1)
57	score = round(sum(subtasks.values()) / len(subtasks), 4)
58	Path("metrics.json").write_text(json.dumps({"score": score, "cost": round(seconds, 2), "subtasks": subtasks}))
59	print(f"{score} of nearest neighbour's tour length on {len(subtasks)} point sets, in {seconds:.1f} s")