Aegean Placement

Twenty real Aegean ports, and the question of where to put a handful of supply depots among them. Asked two ways — and the difference between the two ways is the point.

Nothing here is computed on our side. The page loads a WebAssembly module, Go's runtime bridge and a packed coastline — three static files — and solves everything locally. There is no endpoint behind this page. Nothing on this page touches a chain.

One algorithm has a proof. The other does not.

Max-coverage — guaranteed

Serve as much population as possible within a radius of some depot. Coverage is monotone and submodular, so plain greedy is proven to return at least 63.2% of the true optimum — that is 1 − 1/e, and it is a worst case, known before the solver runs.

p-median — no guarantee

Minimize total weighted travel to the nearest depot. There is no approximation bound for the interchange heuristic that solves it. It is very good in practice and it is guaranteed nothing, and this page never calls its answer optimal.

Up to 4 depots the page also runs an exhaustive search and shows the true optimum beside the heuristic's answer, so you watch the bound hold rather than take our word for it. Past 4 the exhaustive search stops being cheap, and the page says the optimum was not computed rather than going quiet about it.

The map

Problem p-median no guarantee max-coverage proven bound

Depots 3 Seed

Loading the solver…

The answer

The ports

Every port below is a real place, and its weight is its population. Total demand across the 20 ports is 7980753.

The demand points, largest first. Rendered from the dataset on the server, so this table is here whether or not WebAssembly is.
Port	Country	Population	Lat	Lon
Athens	Greece	3242000	37.985	23.731
İzmir	Turkey	2587000	38.438	27.150
Thessaloniki	Greece	828000	40.698	22.883
Piraeus	Greece	466065	37.950	23.700
Iraklio	Greece	137154	35.325	25.130
Volos	Greece	110632	39.370	22.950
Çanakkale	Turkey	87791	40.146	26.406
Hania	Greece	78728	35.512	24.016
Chalkida	Greece	71842	38.464	23.612
Kavala	Greece	59240	40.941	24.402
Rodos	Greece	56969	36.441	28.223
Katerini	Greece	53293	40.272	22.502
Alexandroupoli	Greece	52979	40.849	25.874
Lamia	Greece	47246	38.899	22.434
Mitilini	Greece	29328	39.110	26.555
Hios	Greece	26891	38.368	26.136
Kos	Greece	19244	36.894	27.289
Ermoupoli	Greece	12260	37.450	24.933
Sitia	Greece	8833	35.200	26.099
Polygyros	Greece	5258	40.381	23.453

Where the data comes from

Coastline and ports are Natural Earth 1:10m, public domain. The map is decimated with Ramer-Douglas-Peucker at 0.002°, and that figure is read from the artifact's own header rather than typed here. Ports are the populated places inside the crop that sit within 12 km of a coastline vertex — a computed filter, not a hand-picked list. Population is Natural Earth's POP_MAX, used as the demand weight and nothing else: it is not a claim about a port's throughput or a current census.

The crop stops at the Dardanelles. A box reaching far enough north for Kavala and Alexandroupoli also reaches over the strait and picks up Istanbul, which is not an Aegean port and has more people than the rest of the table combined — every depot would go there and the map would be one dot.

The solver is a separate public module: github.com/pigfox/aegean-solver. p-median interchange, lazy-greedy max-coverage and the distance model, with their own tests and 100% statement coverage. The bound is checked there against exhaustive search over 480 instances rather than cited.