Attributes

Attributes define problem features and automatically enable matching constraint generators and evaluators.

Available Attributes

Attribute	Entity	Description
GeoNode	Node	x, y coordinates for distance calculation
Consumer	Client	Demand at a client
Stock	Vehicle	Vehicle capacity
Rendezvous	Node	Time window bounds (earliest, latest)
ServiceQuery	Client	Service time at a node
Profiter	Client	Profit value for orienteering problems (TOP)
Pickup	Client	Pickup demand for pickup & delivery
Delivery	Client	Delivery demand for pickup & delivery
Synced	Client	Temporal synchronization constraints
SoftTimeWindows	Client	Penalty-based soft time windows

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Problem Variants by Attributes

Problem	Required Attributes
TSP	GeoNode
VRP	GeoNode
CVRP	GeoNode, Consumer, Stock
VRPTW	GeoNode, Rendezvous, ServiceQuery
CVRPTW	GeoNode, Consumer, Stock, Rendezvous, ServiceQuery
TOP	GeoNode, Profiter, Rendezvous
PDVRP	GeoNode, Pickup, Delivery, Stock
VRPTWTD	All above + Synced

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Usage

Python - Low-Level API

Python uses helper functions to set attributes on entities:

import routing

routing.init()

# Create problem
problem = routing.Problem()

# Add depot and set its attributes
depot = problem.add_depot(0)
routing.set_depot_location(depot, 0.0, 0.0)           # GeoNode
routing.set_depot_time_window(depot, 0.0, 1000.0)     # Rendezvous

# Add client and set its attributes
client = problem.add_client(1)
routing.set_client_location(client, 10.0, 20.0)       # GeoNode
routing.set_client_demand(client, 5)                   # Consumer
routing.set_client_time_window(client, 0.0, 200.0)    # Rendezvous
routing.set_client_service_time(client, 10.0)         # ServiceQuery

# Add vehicle and set its attributes
vehicle = problem.add_vehicle(0)
routing.set_vehicle_capacity(vehicle, 100)             # Stock

# Enable the attributes used
problem.enable_attributes(["GeoNode", "Consumer", "Stock", "Rendezvous", "ServiceQuery"])

# Solve
solver = routing.create_solver("ga", problem)
solver.solve(30.0)

Python helper functions → Attributes:

Helper Function	Attribute Set
set_client_location(client, x, y)	GeoNode
set_client_demand(client, demand)	Consumer
set_client_time_window(client, open, close)	Rendezvous
set_client_service_time(client, time)	ServiceQuery
set_vehicle_capacity(vehicle, capacity)	Stock
set_depot_location(depot, x, y)	GeoNode
set_depot_time_window(depot, open, close)	Rendezvous

Python - ProblemBuilder (High-Level)

The ProblemBuilder wraps the low-level API for convenience:

from routing.problem import ProblemBuilder

problem = (ProblemBuilder()
    .with_depot(0, 0, tw_open=0, tw_close=1000)
    .add_client(1, x=10, y=20, demand=5, tw_open=0, tw_close=200, service_time=10)
    .add_vehicles(count=2, capacity=20)
    .build())  # Automatically calls enable_attributes()

C++

In C++, you use template methods to add attributes:

// 1. Enable the attributes you need
problem.enableAttributes<GeoNode, Consumer, Stock, Rendezvous, ServiceQuery>();

// 2. Add depot with attributes
auto* depot = problem.addDepot(0);
depot->addAttribute<GeoNode>(0.0, 0.0);           // Coordinates
depot->addAttribute<Rendezvous>(0.0, 1000.0);     // Operating hours

// 3. Add client with attributes
auto* client = problem.addClient(1);
client->addAttribute<GeoNode>(10.0, 20.0);        // Coordinates
client->addAttribute<Consumer>(5);                 // Demand
client->addAttribute<Rendezvous>(0.0, 200.0);     // Time window
client->addAttribute<ServiceQuery>(10.0);          // Service time

// 4. Add vehicle with attributes
auto* vehicle = problem.addVehicle(0);
vehicle->addAttribute<Stock>(20);                  // Capacity

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How Attributes Work

When you add an attribute to an entity, the system automatically:

1. Registers the attribute with the problem

2. Enables constraint generators that depend on that attribute

3. Enables evaluators for solution quality assessment

Attribute Added → Constraint Generator Activated → Constraints in Model
     ↓
GeoNode        → RoutingGenerator              → Distance objective
Consumer       → CapacityGenerator             → Load ≤ Capacity
Stock          → CapacityGenerator             → Vehicle capacity limit
Rendezvous     → TimeWindowGenerator           → Arrival ∈ [open, close]
ServiceQuery   → TimeWindowGenerator           → Service time in scheduling

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Custom Attributes

You can define custom attributes using the CRTP pattern:

struct MyAttribute : public Attribute<MyAttribute> {
    static constexpr const char* name() { return "MyAttribute"; }

    double value;

    explicit MyAttribute(double v) : value(v) {}
};

See Composable System for more details on extending the attribute system.