Gate a run against a placard

A gate is a named predicate over the recorded rows. It reports; it does not print and does not exit.

let gates = GateSeq::new()
    .add("q-max placard", |rows| {
        let peak = rows.iter().map(|r| r.q_kpa).fold(f64::MIN, f64::max);
        if peak <= Q_PLACARD_KPA {
            GateOutcome::pass(format!("max q = {peak:.1} kPa, inside the {Q_PLACARD_KPA} kPa placard"))
        } else {
            GateOutcome::fail(format!("q = {peak:.1} kPa exceeds the {Q_PLACARD_KPA} kPa placard"))
        }
    });

verdict() resolves the study to a Verdict. Mapping it to an exit code is the caller’s responsibility, so the same study serves as a CI gate in one binary and a report in another.

Write the number into the message

Every gate message in this crate carries the measured value and the limit:

[PASS] q-max placard: max q = 23.7 kPa at M 1.20 / 11.0 km, inside the 60 kPa placard
[FAIL] q-max placard: q = 85.1 kPa at M 1.50 / 5.0 km exceeds the 60 kPa placard

A bare [PASS] records only the outcome. Including the measured value and the limit records the remaining margin: a pass at 58 kPa against a 60 kPa placard and a pass at 24 kPa carry different information.

Gate the validated band

The VIV example checks Strouhal against [0.16, 0.21], described as the validated band for that grid, rather than against the literature value. Coarse grids bias Strouhal high, so a literature gate would fail correct runs at affordable resolution.

The convention across the crate is to pin the band from a measured run and then gate regressions against it.

A passing gate is not a passing physics target

In the retropulsion studies, “GATES PASSED” appears above a recorded miss against the Jarvinen–Adams reference. The gate protects a negative finding from regressing. Its claim is that the measured structure is reproducible.

Read what each gate asserts before treating a green run as validation. See capability boundaries.

Gate for the detectable failure mode

A wake march that decays to steady produces a finite signal, and a frequency extractor will report noise as a frequency. The VIV example gates on a finite, oscillating wake rather than on finiteness alone. The cylinder verification records the failure mode: with a staircase boundary the wake decays and the detector reports St ≈ 0.244 from seventh-decimal noise.

Worked examples using this

• Flight envelope placard
• Nozzle operating map