consortium-fanout-sim

Deterministic in-process simulator for the cascade primitive. Computes per-edge durations from closure_size / bandwidth + latency, applies failure schedules, and returns results to the cascade coordinator.

No real networking, no async runtime, no SSH. Each Scenario is reproducible from a u64 seed — same seed produces identical CascadeResult including round count and error tree shape.

Layout

• [executor::DeterministicExecutor] — implements RoundExecutor with bandwidth/latency-driven timing and an injectable failure schedule.
• [fixtures] — generators for seed sets, bandwidth distributions, and failure schedules. Each takes &mut StdRng for reproducibility.
• [scenario::Scenario] — high-level wrapper that builds a complete cascade run (nodes + seeded set + network + executor + strategy) from a seed and a few descriptors.

Quick start

use consortium_fanout_sim::scenario::{Scenario, ScenarioConfig};
use consortium_fanout_sim::fixtures::BandwidthDistribution;
use consortium_nix::cascade::Log2FanOut;

let cfg = ScenarioConfig {
    seed: 0xc0ffee,
    n_nodes: 64,
    seed_fraction: 0.0,
    closure_bytes: 100 * 1024 * 1024,
    bandwidth: BandwidthDistribution::Uniform(100 * 1024 * 1024),
    uplinks: None,
    failures: Default::default(),
    max_rounds: 32,
};
let result = Scenario::new(cfg).run(&Log2FanOut);
assert!(result.is_success());
assert_eq!(result.converged.len(), 64);