Tutorial 4 — Built-in Topology Generators

Objective: Generate and inspect three pre-built topology templates to understand qnet-core's ready-made network configurations.

qnet-core ships with generate_topology() — a factory function that creates realistic network topologies programmatically. This saves you from manually defining every node and link.

Generate All Three Topologies

from qnet_core import QNetEngine, generate_topology

for name in ("telecom_backbone", "repeater_chain", "hybrid_satellite_fiber"):
    print(f"\n=== {name} ===")
    payload = generate_topology(name)
    
    print(f"  Nodes ({len(payload.nodes)}): {[n.id for n in payload.nodes]}")
    print(f"  Links ({len(payload.links)}):")
    for link in payload.links:
        link_type = getattr(link.link_type, "_name", "Fiber") or "Fiber"
        extra = ""
        if hasattr(link, "satellite_conditions") and link.satellite_conditions:
            cond = link.satellite_conditions
            extra = f" [satellite vis={cond.visibility:.1f} weather={cond.weather_factor:.1f}]"
        print(f"    {link.from_node} → {link.to}: {link.distance_km:.0f} km, "
              f"fidelity={link.base_fidelity:.2f}, rate={link.generation_rate_hz:.0f} Hz{extra}")

Topology Reference

Name	Type	Description
telecom_backbone	Mesh fiber network	Urban telecom-style mesh with intermediate repeaters, mimicking real fiber backbone layouts
repeater_chain	Linear chain (4 hops)	Point-to-point repeater chain — ideal for testing purification across multiple segments
hybrid_satellite_fiber	Satellite + fiber mix	Hybrid network with a satellite uplink and fiber ground segments

Use a Generated Topology in Simulation

engine = QNetEngine()
payload = generate_topology("telecom_backbone")
engine.define_network(payload.nodes, payload.links)

nodes_ids = [n.id for n in payload.nodes]
if len(nodes_ids) >= 2:
    stats = engine.simulate(
        from_node=nodes_ids[0],
        to=nodes_ids[-1],
        fidelity_target=0.85,
        max_latency_ms=10_000.0,
        runs=100,
        seed=42,
    )
    print(f"Success rate:   {stats.empirical_success_rate:.1%}")
    print(f"Mean latency:   {stats.mean_latency_ms:.1f} ms")
    print(f"Mean fidelity:  {stats.mean_fidelity:.4f}")

What's next

• Satellite-Fiber Links — explore satellite conditions in detail
• Basic Entanglement Request — manual topology definition