nigig-org/crates/apps/nigig-traffic/tests/perf.rs

//! Perf baseline harness (plan Phase 6.3).
//!
//! Measures world-build and fixed-step tick costs and prints medians. The
//! timings are NOT asserted — wall-clock asserts are flaky by nature (HPC
//! ch.5.6). The sanity asserts only prove the sim actually ran (tick count,
//! phase transition, black-boxed state) so the optimizer cannot hollow the
//! loop. Run pinned on one machine and copy the table into
//! `docs/PERF_BASELINE.md` by hand:
//!
//! ```sh
//! cargo test -p nigig-traffic --test perf -- --test-threads=1 --nocapture
//! ```

use nigig_traffic::traffic::road::build_world_for;
use nigig_traffic::traffic::scenario::all;
use nigig_traffic::traffic::{Phase, TrafficWorld};
use std::hint::black_box;
use std::time::Instant;

fn median_us(mut samples: Vec<u128>) -> u128 {
    samples.sort_unstable();
    samples[samples.len() / 2]
}

#[test]
fn perf_print_baseline() {
    let scenarios = all();
    println!(
        "=== nigig-traffic perf baseline ({} scenarios) ===",
        scenarios.len()
    );

    // 1. World build per category (first scenario of each), 20 reps.
    println!("--- build_world_for: median µs over 20 reps ---");
    let mut seen_cats = Vec::new();
    for s in scenarios {
        if seen_cats.contains(&s.category) {
            continue;
        }
        seen_cats.push(s.category);
        let mut samples = Vec::with_capacity(20);
        for _ in 0..20 {
            let mut world = makepad_game_sim::GameWorld::new();
            let mut next_id = 1u64;
            let t0 = Instant::now();
            let meta = build_world_for(&mut world, s, &mut next_id);
            let us = t0.elapsed().as_micros();
            // Touch the outputs so the build cannot be eliminated.
            black_box(meta.finish_radius);
            black_box(world.entities.len());
            samples.push(us);
        }
        println!(
            "  {:<10} {:>6} µs",
            format!("{:?}", s.category),
            median_us(samples)
        );
    }

    // 2. Fixed-step tick: 600 ticks per scenario, default (idle) input.
    // Reports median per-tick µs across scenarios plus the slowest three.
    println!("--- tick: 600 ticks/scenario, per-tick µs ---");
    let mut per_tick: Vec<(&str, u128)> = Vec::new();
    for (i, s) in scenarios.iter().enumerate() {
        let mut world = TrafficWorld::new();
        world.load_scenario(i);
        let input = makepad_game_blocks::DriveInput::default();
        let t0 = Instant::now();
        for _ in 0..600 {
            world.tick(&input);
        }
        let us = t0.elapsed().as_micros() / 600;
        // Sanity: the sim really ran (intro is 60 ticks) and state escaped.
        assert_eq!(world.run.tick, 600);
        assert_eq!(world.run.phase, Phase::Driving);
        black_box(world.run.score.total_points);
        let _ = s;
        per_tick.push((s.id, us));
    }
    per_tick.sort_by_key(|(_, us)| *us);
    let mid = per_tick[per_tick.len() / 2].1;
    println!("  scenarios: {}, median per-tick: {mid} µs", per_tick.len());
    println!("  slowest 3:");
    for (id, us) in per_tick.iter().rev().take(3) {
        println!("    {id:<22} {us:>6} µs");
    }
    println!("=== end baseline ===");
}