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Calculon

Calculon Logo

"Why can't I move on?"

Calculon is a high-performance, Valhalla-compatible routing engine written in Rust. It provides turn-by-turn navigation using bidirectional A* pathfinding on hierarchical graph tiles.

It reads binary Valhalla-format graph tiles and exposes an HTTP API compatible with Valhalla's JSON format — making it a drop-in replacement for routing workloads.

Features

Fast

Bidirectional A* search with pre-computed lookup tables for O(1) speed factors and turn costs. CPU-bound work runs in spawn_blocking tasks while the Axum server stays async.

Turn-by-turn navigation

Full maneuver building with localized narrative instructions in 36+ languages.

Distance/time matrices

Many-to-many distance and time computation via CostMatrix with hierarchical graph expansion and shortcut edges.

Valhalla-compatible

Same tile format, same JSON API. Point your existing Valhalla tiles at Calculon and go.

Multiple travel modes

Driving (auto), cycling (bicycle), and walking (pedestrian) cost models with rich tuning options.

Quick start

# Build
cargo build -p calculon --release

# Run
./target/release/calculon --tile-dir /path/to/valhalla/tiles

# Route request
curl -s http://localhost:8002/route -d '{
  "locations": [
    {"lat": 48.8566, "lon": 2.3522},
    {"lat": 48.8606, "lon": 2.3376}
  ],
  "costing": "auto"
}' | jq '.trip.summary'

Installation & build

Endpoints

Endpoint Description
POST /route Turn-by-turn routing
POST /sources_to_targets Many-to-many distance/time matrix
POST /debug/inspect Inspect graph connectivity at a junction
POST /debug/cost Cost breakdown for edges at a junction
GET /status Server health check

API reference

Next steps