rtx-fsi: stall acceptance as a knob (STALLX) — the floor must stay tight; only the rare-event window widens

FSI3's developed cycle stalls (bistable mask flips at max-velocity crossings) sit at 3.5e-4 against the measured floor 6e-5: run 3 died 16% over the 5x window at t = 7.70. Riding the FLOOR up instead was measured to make it worse — run 4 at floor 1e-4 died EARLIER (t = 6.30) at a HIGHER stall (1.2e-3, 2.4x its window), because the accepted-step scatter IS the wall-velocity noise (tol/dt_c): a looser floor feeds the flip noise it is trying to pass. Keep the floor tight and widen only the counted, bounded stall window: `stall_accept` (RTX_<CASE>_STALLX, default 5 — both committed defaults bit-identical). Precedent: FSI2's s = 1 benchmark run accepted a worst stall of 5.4e-4 the same way and measured 0.1% in amplitude. Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01Lnyrw33Lu6rUhW42E9KHwq
2026-08-25 05:00:56 -05:00
parent 647f247601
commit 992cd76449
3 changed files with 28 additions and 6 deletions
@@ -103,6 +103,11 @@ fn fsi3_added_mass_flag() {
            // velocities of ~1 m/s.
            tol_floor: 6e-5,
            rtol: 1e-2,
+            // 5 at the committed horizon (t_end 4.2 never stalls); the
+            // t = 10 studies run STALLX=10 — see the MarchConfig field:
+            // the developed cycle's bistable stalls sit at 3.5e-4 and
+            // riding the FLOOR up instead was measured to make it worse.
+            stall_accept: 5.0,
            max_subiterations: 30,
            coupler: "iqn".into(),
            reuse: 2,