Simulation lifecycle

Nexosim runs a discrete-event simulation by repeatedly:

1. executing all events scheduled for the current simulation time
2. advancing to the next time at which at least one event is scheduled

In Days, the main entrypoint is Topology::run, which:

• builds a SimInit
• registers all models and mailboxes
• calls init(...) to obtain a Simulation
• runs sim.step_until(Duration::from_secs_f64(duration))

Key APIs

Source: days/crates/nexosim/src/simulation.rs

• SimInit: builder for assembling a bench (models, mailboxes, runtime knobs)
• Simulation:
  • process_event(...): inject an event/request into a model (often used for “start” actions)
  • step(): advance to the next event time and process all events at that time
  • step_until(Duration): run until a target time

Ordering and determinism

Within a given simulated timestamp, Nexosim may execute ready tasks in parallel (depending on executor configuration). Days therefore avoids treating wall-clock execution order as semantically meaningful and relies on deterministic trace canonicalization for verification (see /docs/verification/design).