feat: new router and benchmark setup

tests/smoke.rs

@@ -221,3 +221,54 @@ fn ablate_rejects_belady_until_exact_algorithm_exists() {
         "unexpected error: {err:#}"
     );
 }
+
+#[test]
+fn ablation_parallel_matches_serial() {
+    let tmp = std::env::temp_dir().join("kvcache_sim_ablate_parallel");
+    let _ = std::fs::remove_dir_all(&tmp);
+    std::fs::create_dir_all(&tmp).unwrap();
+    let trace_path = tmp.join("trace.jsonl");
+    write_synthetic_trace(&trace_path);
+
+    let cfg = base_config(
+        trace_path.to_str().unwrap(),
+        tmp.to_str().unwrap(),
+        RouterMode::Random,
+    );
+    let routers = [
+        RouterMode::Random,
+        RouterMode::LeastLoaded,
+        RouterMode::TtlAware,
+        RouterMode::Precise,
+    ];
+
+    let serial = driver::ablate_fixed_placement_with_parallelism(
+        &cfg,
+        &routers,
+        &[ReplayEvictPolicy::Lru],
+        1,
+    )
+    .expect("serial ablate");
+    let parallel = driver::ablate_fixed_placement_with_parallelism(
+        &cfg,
+        &routers,
+        &[ReplayEvictPolicy::Lru],
+        2,
+    )
+    .expect("parallel ablate");
+
+    assert_eq!(parallel.len(), serial.len());
+    for (lhs, rhs) in parallel.iter().zip(serial.iter()) {
+        assert_eq!(lhs.router, rhs.router);
+        assert_eq!(lhs.evict_policy, rhs.evict_policy);
+        assert_eq!(lhs.placement_source, rhs.placement_source);
+        assert!((lhs.ttft_mean - rhs.ttft_mean).abs() < 1e-9);
+        assert!((lhs.ttft_p50 - rhs.ttft_p50).abs() < 1e-9);
+        assert!((lhs.ttft_p95 - rhs.ttft_p95).abs() < 1e-9);
+        assert!((lhs.ttft_p99 - rhs.ttft_p99).abs() < 1e-9);
+        assert!((lhs.hit_rate_l0 - rhs.hit_rate_l0).abs() < 1e-12);
+        assert!((lhs.hit_rate_l1 - rhs.hit_rate_l1).abs() < 1e-12);
+        assert!((lhs.hit_rate_remote - rhs.hit_rate_remote).abs() < 1e-12);
+        assert!((lhs.miss_rate - rhs.miss_rate).abs() < 1e-12);
+    }
+}