//! embedded3 item 11a: the fresh-cell falsifier of the 2D track
//! (`embedded_fresh_cell_falsifier.rs`, omni-cortex
//! `docs/fresh_cell_gcl_campaign.md`) on the 3D solver, per unit span —
//! the rigid Turek–Hron flag (0.35 × 0.02 m) extruded across a periodic
//! slab, oscillating transversely in still fluid at the flag's tip speed
//! (1 m/s peak, 80 mm amplitude) on h = 1/152 at dt = 3.24e-4. Per step:
//! the load per unit span (the ghost wall's traction route over the
//! plate's samples; the cut wall's operator route), a far-field pressure
//! probe, the fluid's kinetic energy, the fresh-cell count.
//!
//! Registered gates (`docs/embedded3_campaign.md` item 11):
//! - GhostBinary reproduces the 2D wall's impulse: energy per flipped
//!   column within 30 % of the 2D 0.048 J/m per flipped cell, spike RMS
//!   exponent in dt ≈ −1 (published −0.8 for the raw volume source);
//! - CutCell: energy per fresh column ≥ 20× lower, max force spike < 5 %
//!   of ½ρU²L, exponent ∈ [−0.3, 0.3].
//!
//! Default run: dt only, both schemes (minutes on the host);
//! `RTX_E3_FALSIFIER_LADDER=1` runs dt, dt/2, dt/4 and fits the exponent
//! (the gated variant is `#[ignore]`); `RTX_E3_FALSIFIER_NZ` sets the
//! span in cells (default 4); `RTX_E3_FALSIFIER_CSV=<dir>` dumps records.

use rtx_cfd::solvers::incompressible::ConvectionScheme;
use rtx_cfd::solvers::incompressible::embedded3::{
    Body, Boundaries, Field, Fluid, Grid, Parameters, Side, Solver, WallScheme,
};
use std::io::Write as _;

const RHO: f64 = 1000.0;
const MU: f64 = 1.0;
const N: usize = 152;
const DT_FSI2: f64 = 3.24e-4;
const HX: f64 = 0.175;
const HY: f64 = 0.01;
const AMP: f64 = 0.08;
const U_PEAK: f64 = 1.0;
const CX: f64 = 0.5;
const CY0: f64 = 0.5;
/// The 2D wall's measured energy per flipped cell (J/m at U = 1, h = 1/152).
const ENERGY_2D: f64 = 0.048;

fn span_cells() -> usize {
    std::env::var("RTX_E3_FALSIFIER_NZ")
        .ok()
        .and_then(|v| v.parse().ok())
        .unwrap_or(4)
}

fn center_y(t: f64) -> f64 {
    CY0 + AMP * (U_PEAK / AMP * t).sin()
}

fn center_v(t: f64) -> f64 {
    U_PEAK * (U_PEAK / AMP * t).cos()
}

fn plate_sdf(x: f64, y: f64, yc: f64) -> f64 {
    let qx = (x - CX).abs() - HX;
    let qy = (y - yc).abs() - HY;
    let outside = (qx.max(0.0).powi(2) + qy.max(0.0).powi(2)).sqrt();
    outside + qx.max(qy).min(0.0)
}

const R_CIRCLE: f64 = 0.05;

/// `RTX_E3_FALSIFIER_BODY=circle`: the 2D falsifier's smooth body (a
/// cylinder of radius 0.05 across the span) instead of the plate.
fn circle_body() -> bool {
    std::env::var("RTX_E3_FALSIFIER_BODY").is_ok_and(|v| v == "circle")
}

/// `RTX_E3_FALSIFIER_BODY=stadium`: the plate with semicircular ends
/// (radius `HY`): the same length and thickness, a smooth interface for
/// the cut geometry's linear interpolant.
fn stadium_body() -> bool {
    std::env::var("RTX_E3_FALSIFIER_BODY").is_ok_and(|v| v == "stadium")
}

fn stadium_sdf(x: f64, y: f64, yc: f64) -> f64 {
    let half = HX - HY;
    let qx = (x - CX).abs().max(half) - half;
    (qx * qx + (y - yc).powi(2)).sqrt() - HY
}

fn plate(moving: bool) -> Body {
    let yc = move |t: f64| if moving { center_y(t) } else { CY0 };
    let vc = move |t: f64| if moving { center_v(t) } else { 0.0 };
    if circle_body() {
        return Body::from_sdf(move |x, y, _z, t| {
            ((x - CX).powi(2) + (y - yc(t)).powi(2)).sqrt() - R_CIRCLE
        })
        .with_surface_velocity(move |_, _, _, t| (0.0, vc(t), 0.0));
    }
    if stadium_body() {
        return Body::from_sdf(move |x, y, _z, t| stadium_sdf(x, y, yc(t)))
            .with_surface_velocity(move |_, _, _, t| (0.0, vc(t), 0.0));
    }
    Body::from_sdf(move |x, y, _z, t| plate_sdf(x, y, yc(t)))
        .with_surface_velocity(move |_, _, _, t| (0.0, vc(t), 0.0))
}

/// The load scale `½ρU²L` of the body (its length across the motion).
fn load_scale() -> f64 {
    let l = if circle_body() {
        2.0 * R_CIRCLE
    } else {
        2.0 * HX
    };
    0.5 * RHO * U_PEAK * U_PEAK * l
}

/// Surface samples of the plate at `t`: `(x, y, z, nx, ny, area)` over the
/// four edges at spacing `ds` and `nz` z levels.
fn samples(
    t: f64,
    moving: bool,
    ds: f64,
    nz: usize,
    dz: f64,
) -> Vec<(f64, f64, f64, f64, f64, f64)> {
    let yc = if moving { center_y(t) } else { CY0 };
    let mut out = Vec::new();
    if circle_body() {
        let n = ((2.0 * std::f64::consts::PI * R_CIRCLE / ds).ceil() as usize).max(8);
        let dth = 2.0 * std::f64::consts::PI / n as f64;
        for k in 0..n {
            let th = (k as f64 + 0.5) * dth;
            let (sn, cs) = th.sin_cos();
            for kz in 0..nz {
                out.push((
                    CX + R_CIRCLE * cs,
                    yc + R_CIRCLE * sn,
                    (kz as f64 + 0.5) * dz,
                    cs,
                    sn,
                    R_CIRCLE * dth * dz,
                ));
            }
        }
        return out;
    }
    if stadium_body() {
        let half = HX - HY;
        let n_flat = ((2.0 * half / ds).ceil() as usize).max(1);
        for k in 0..n_flat {
            let x = CX - half + (k as f64 + 0.5) / n_flat as f64 * 2.0 * half;
            for kz in 0..nz {
                let z = (kz as f64 + 0.5) * dz;
                let a = 2.0 * half / n_flat as f64 * dz;
                out.push((x, yc + HY, z, 0.0, 1.0, a));
                out.push((x, yc - HY, z, 0.0, -1.0, a));
            }
        }
        let n_arc = ((std::f64::consts::PI * HY / ds).ceil() as usize).max(4);
        for (cx, sign) in [(CX + half, 1.0), (CX - half, -1.0)] {
            for k in 0..n_arc {
                let th = -std::f64::consts::FRAC_PI_2
                    + (k as f64 + 0.5) / n_arc as f64 * std::f64::consts::PI;
                let (sn, cs) = th.sin_cos();
                let (nx, ny) = (sign * cs, sn);
                for kz in 0..nz {
                    out.push((
                        cx + HY * nx,
                        yc + HY * ny,
                        (kz as f64 + 0.5) * dz,
                        nx,
                        ny,
                        std::f64::consts::PI * HY / n_arc as f64 * dz,
                    ));
                }
            }
        }
        return out;
    }
    let (x0, x1, y0, y1) = (CX - HX, CX + HX, yc - HY, yc + HY);
    let mut edge = |ax: f64, ay: f64, bx: f64, by: f64, nx: f64, ny: f64| {
        let len = ((bx - ax).powi(2) + (by - ay).powi(2)).sqrt();
        let n = ((len / ds).ceil() as usize).max(1);
        for k in 0..n {
            let s = (k as f64 + 0.5) / n as f64;
            for kz in 0..nz {
                out.push((
                    ax + s * (bx - ax),
                    ay + s * (by - ay),
                    (kz as f64 + 0.5) * dz,
                    nx,
                    ny,
                    len / n as f64 * dz,
                ));
            }
        }
    };
    edge(x0, y0, x1, y0, 0.0, -1.0);
    edge(x1, y0, x1, y1, 1.0, 0.0);
    edge(x1, y1, x0, y1, 0.0, 1.0);
    edge(x0, y1, x0, y0, -1.0, 0.0);
    out
}

struct Record {
    t: f64,
    /// Load per unit span (the scheme's wall route).
    fy: f64,
    /// Load per unit span by the control-volume route (a box of whole
    /// cells around the body, reading no near-wall value).
    fy_cv: f64,
    /// The inertia floor's momentum source per unit span (cut wall).
    fy_floor: f64,
    /// The pressure corrections' closure lag per unit span (cut wall).
    fy_lag: f64,
    /// The force the momentum equation applied (shear on u*, exchange on uⁿ).
    fy_applied: f64,
    fresh: usize,
    skipped: usize,
    p_far: f64,
    /// Kinetic energy per unit span over the fluid cells.
    ke: f64,
}

struct Run {
    records: Vec<Record>,
    /// The largest kinetic-energy change per step at a step with fresh
    /// cells (after the impulsive start) over that step's flipped columns
    /// (J/m) — the 2D falsifier's 2.604 J/m over 54 cells = 0.048.
    energy_per_flip: f64,
    seconds: f64,
}

fn run(scheme: WallScheme, moving: bool, dt: f64, t_end: f64) -> Run {
    let nz = span_cells();
    let h = 1.0 / N as f64;
    let lz = nz as f64 * h;
    let mut solver = Solver::new(
        Fluid {
            density: RHO,
            viscosity: MU,
            reference_velocity: 1.0,
            reference_length: 2.0 * HY,
        },
        Parameters {
            corrector_steps: 2,
            tolerance: 1e-8,
            convection_scheme: ConvectionScheme::Upwind,
            wall_scheme: scheme,
            boundaries: Boundaries {
                z0: Side::Periodic,
                z1: Side::Periodic,
                ..Boundaries::default()
            },
            max_surface_speed: Some(U_PEAK),
            // `RTX_E3_SUBSTEPS`: intermediate geometries for the space-time apertures.
            aperture_substeps: std::env::var("RTX_E3_SUBSTEPS")
                .ok()
                .and_then(|v| v.parse().ok())
                .unwrap_or(0),
            // `RTX_E3_CELL_MEAN=1`: the momentum volume from the two cells' fractions.
            momentum_volume_cell_mean: std::env::var("RTX_E3_CELL_MEAN").is_ok_and(|v| v == "1"),
            ..Parameters::default()
        },
    );
    solver.set_boundary_velocity(|_, _, _, _| (0.0, 0.0, 0.0));
    if moving {
        solver.set_moving_body(plate(true));
    } else {
        solver.set_body(plate(false));
    }
    let g = Grid::cubic(N, N, nz, h);
    let mut field = Field::new(g);
    solver.initialize(&mut field);
    let steps = (t_end / dt).round() as usize;
    let mut records = Vec::with_capacity(steps);
    // The 2D definition: the largest |ΔKE| step's energy over that
    // step's flipped columns.
    let mut largest_jump = 0.0_f64;
    let mut energy_per_flip = 0.0_f64;
    let mut ke_prev: Option<f64> = None;
    let start = std::time::Instant::now();
    let (jp, ip, kp) = (
        (0.92 * N as f64) as usize,
        (0.5 * N as f64) as usize,
        nz / 2,
    );
    for step in 0..steps {
        let result = solver.advance(&mut field, dt);
        let t = (step + 1) as f64 * dt;
        let mask = solver.mask().expect("mask");
        let body = solver.body().expect("body");
        let (mut fy, mut skipped) = (0.0, 0usize);
        match scheme {
            WallScheme::GhostBinary => {
                for (x, y, z, nx, ny, area) in samples(t, moving, 0.5 * h, nz, h) {
                    match mask.traction_at(body, &field, MU, t, [x, y, z], [nx, ny, 0.0]) {
                        Some(tr) => fy += tr[1] * area,
                        None => skipped += 1,
                    }
                }
            }
            WallScheme::CutCell => {
                fy = mask.cut_wall_force(body, &field, MU, t).expect("cut wall")[1];
            }
        }
        fy /= lz;
        let fy_floor = solver.floor_source()[1] / lz;
        let fy_lag = solver.pressure_lag()[1] / lz;
        let fy_applied = if scheme == WallScheme::CutCell {
            mask.cut_wall_force_applied(body, &field, MU, RHO, t)
                .expect("applied")[1]
                / lz
        } else {
            0.0
        };
        let margin = 8;
        let fy_cv = mask.control_volume_force_moving(
            &field,
            dt,
            RHO,
            MU,
            None,
            (margin, N - margin, margin, N - margin, 0, nz),
            false,
            solver.previous_volumes(),
        )[1] / lz;
        let p_far = field.p[g.cell(kp, jp, ip)];
        let mut ke = 0.0;
        for k in 0..nz {
            for j in 0..N {
                for i in 0..N {
                    let idx = g.cell(k, j, i);
                    if mask.is_fluid_cell(idx) {
                        let uc = 0.5 * (field.u[g.uface(k, j, i)] + field.u[g.uface(k, j, i + 1)]);
                        let vc = 0.5 * (field.v[g.vface(k, j, i)] + field.v[g.vface(k, j + 1, i)]);
                        let wc = 0.5 * (field.w[g.wface(k, j, i)] + field.w[g.wface(k + 1, j, i)]);
                        ke += 0.5 * RHO * (uc * uc + vc * vc + wc * wc) * h * h * h * mask.vol(idx);
                    }
                }
            }
        }
        ke /= lz;
        if let Some(prev) = ke_prev {
            if step > 30 && result.fresh_cells > 0 && (ke - prev).abs() > largest_jump {
                largest_jump = (ke - prev).abs();
                // The plate's event is its row (the 2D divided by the row's
                // 54 cells); the circle's is the step's fresh columns.
                let columns = if circle_body() {
                    result.fresh_cells as f64 / nz as f64
                } else {
                    (2.0 * HX / h).round()
                };
                energy_per_flip = largest_jump / columns;
            }
        }
        ke_prev = Some(ke);
        records.push(Record {
            t,
            fy,
            fy_cv,
            fy_floor,
            fy_lag,
            fy_applied,
            fresh: result.fresh_cells,
            skipped,
            p_far,
            ke,
        });
    }
    if scheme == WallScheme::CutCell {
        let n = records.len().max(1) as f64;
        let rms = |f: &dyn Fn(&Record) -> f64| {
            (records.iter().map(|r| f(r) * f(r)).sum::<f64>() / n).sqrt()
        };
        let mean = |f: &dyn Fn(&Record) -> f64| records.iter().map(f).sum::<f64>() / n;
        println!(
            "    route residual (wall − box) RMS {:.3e} → with the floor source {:.3e}, with the closure lag {:.3e}, both {:.3e}, APPLIED form {:.3e} (mean {:+.3e}); means wall {:+.3e} box {:+.3e} floor {:+.3e} lag {:+.3e}; box RMS {:.3e}",
            rms(&|r| r.fy - r.fy_cv),
            rms(&|r| r.fy + r.fy_floor - r.fy_cv),
            rms(&|r| r.fy + r.fy_lag - r.fy_cv),
            rms(&|r| r.fy + r.fy_floor + r.fy_lag - r.fy_cv),
            rms(&|r| r.fy_applied - r.fy_cv),
            mean(&|r| r.fy_applied),
            mean(&|r| r.fy),
            mean(&|r| r.fy_cv),
            mean(&|r| r.fy_floor),
            mean(&|r| r.fy_lag),
            rms(&|r| r.fy_cv)
        );
    }
    Run {
        records,
        energy_per_flip,
        seconds: start.elapsed().as_secs_f64(),
    }
}

/// Spike series: the load minus its 21-step running median.
fn spikes(f: &[f64]) -> Vec<f64> {
    let w = 10usize;
    (0..f.len())
        .map(|k| {
            let lo = k.saturating_sub(w);
            let hi = (k + w + 1).min(f.len());
            let mut win: Vec<f64> = f[lo..hi].to_vec();
            win.sort_by(|a, b| a.partial_cmp(b).unwrap());
            f[k] - win[win.len() / 2]
        })
        .collect()
}

struct Stats {
    rms_force: f64,
    rms_spike: f64,
    max_spike: f64,
    rms_spike_cv: f64,
    max_spike_cv: f64,
    rms_pfar_spike: f64,
    max_pfar_spike: f64,
    max_ke_jump: f64,
    fresh_total: usize,
    skipped_max: usize,
}

fn stats(records: &[Record], t_lo: f64, t_hi: f64) -> Stats {
    let fy: Vec<f64> = records.iter().map(|r| r.fy).collect();
    let sp = spikes(&fy);
    let fcv: Vec<f64> = records.iter().map(|r| r.fy_cv).collect();
    let spc = spikes(&fcv);
    let pf: Vec<f64> = records.iter().map(|r| r.p_far).collect();
    let spf = spikes(&pf);
    let idx: Vec<usize> = (0..records.len())
        .filter(|&k| records[k].t >= t_lo && records[k].t <= t_hi)
        .collect();
    let rms = |v: &dyn Fn(usize) -> f64| {
        (idx.iter().map(|&k| v(k) * v(k)).sum::<f64>() / idx.len().max(1) as f64).sqrt()
    };
    Stats {
        rms_force: rms(&|k| fy[k]),
        rms_spike: rms(&|k| sp[k]),
        max_spike: idx.iter().map(|&k| sp[k].abs()).fold(0.0, f64::max),
        rms_spike_cv: rms(&|k| spc[k]),
        max_spike_cv: idx.iter().map(|&k| spc[k].abs()).fold(0.0, f64::max),
        rms_pfar_spike: rms(&|k| spf[k]),
        max_pfar_spike: idx.iter().map(|&k| spf[k].abs()).fold(0.0, f64::max),
        max_ke_jump: idx
            .iter()
            .filter(|&&k| k > 0)
            .map(|&k| (records[k].ke - records[k - 1].ke).abs())
            .fold(0.0, f64::max),
        fresh_total: idx.iter().map(|&k| records[k].fresh).sum(),
        skipped_max: idx.iter().map(|&k| records[k].skipped).max().unwrap_or(0),
    }
}

fn dump(dir: &str, name: &str, records: &[Record]) {
    let path = std::path::Path::new(dir).join(format!("{name}.csv"));
    let mut f = std::fs::File::create(path).expect("csv");
    writeln!(f, "t,fy,fy_cv,fresh,skipped,p_far,ke").unwrap();
    for r in records {
        writeln!(
            f,
            "{:.6},{:.6e},{:.6e},{},{},{:.6e},{:.6e}",
            r.t, r.fy, r.fy_cv, r.fresh, r.skipped, r.p_far, r.ke
        )
        .unwrap();
    }
}

struct Verdict {
    energy_per_flip: f64,
    max_spike: f64,
    exponent: Option<f64>,
}

fn falsify(scheme: WallScheme, ladder: bool) -> Verdict {
    let csv_dir = std::env::var("RTX_E3_FALSIFIER_CSV").ok();
    let period = 2.0 * std::f64::consts::PI * AMP / U_PEAK;
    let t_end = 0.3 * period;
    let (t_lo, t_hi) = (0.02 * period, 0.28 * period);
    let rest = run(scheme, false, DT_FSI2, t_end);
    let s0 = stats(&rest.records, t_lo, t_hi);
    println!(
        "  {scheme:?} plate AT REST, dt {DT_FSI2:.2e} ({:.0} s): rms force {:.3e}, rms spike {:.3e}, max spike {:.3e}, fresh {}, skipped max {}",
        rest.seconds, s0.rms_force, s0.rms_spike, s0.max_spike, s0.fresh_total, s0.skipped_max
    );
    if let Some(d) = &csv_dir {
        dump(d, &format!("{scheme:?}_rest"), &rest.records);
    }
    let dts: Vec<f64> = if ladder {
        vec![DT_FSI2, DT_FSI2 / 2.0, DT_FSI2 / 4.0]
    } else {
        vec![DT_FSI2]
    };
    let mut points = Vec::new();
    let mut energy = 0.0_f64;
    let mut max_spike = 0.0_f64;
    for &dt in &dts {
        let r = run(scheme, true, dt, t_end);
        let s = stats(&r.records, t_lo, t_hi);
        println!(
            "  {scheme:?} plate MOVING, dt {dt:.3e} ({} steps, {:.0} s): rms force {:.3e}, rms spike {:.3e} ({:.1}x rest), max spike {:.3e} N/m ({:.2e} of ½ρU²L), fresh cells {} ({:.2}/step), skipped max {}",
            r.records.len(),
            r.seconds,
            s.rms_force,
            s.rms_spike,
            s.rms_spike / s0.rms_spike.max(1e-300),
            s.max_spike,
            s.max_spike / load_scale(),
            s.fresh_total,
            s.fresh_total as f64 / r.records.len() as f64,
            s.skipped_max
        );
        println!(
            "    control-volume route: rms spike {:.3e}, max spike {:.3e} N/m ({:.2e} of ½ρU²L)",
            s.rms_spike_cv,
            s.max_spike_cv,
            s.max_spike_cv / load_scale()
        );
        println!(
            "    far probe p(0.5, 0.92): rms spike {:.3e}, max spike {:.3e}; max |ΔKE| per step {:.3e} J/m; energy per flipped column {:.3e} J/m ({:.2} of the 2D wall's {ENERGY_2D})",
            s.rms_pfar_spike,
            s.max_pfar_spike,
            s.max_ke_jump,
            r.energy_per_flip,
            r.energy_per_flip / ENERGY_2D
        );
        if let Some(d) = &csv_dir {
            dump(d, &format!("{scheme:?}_moving_dt{dt:.3e}"), &r.records);
        }
        assert!(s.rms_force.is_finite() && s.rms_spike.is_finite());
        if dt == DT_FSI2 {
            energy = r.energy_per_flip;
            max_spike = s.max_spike;
        }
        points.push((dt, s.rms_spike));
    }
    let exponent = (points.len() >= 2).then(|| {
        let xs: Vec<f64> = points.iter().map(|p| p.0.ln()).collect();
        let ys: Vec<f64> = points.iter().map(|p| p.1.ln()).collect();
        let mx = xs.iter().sum::<f64>() / xs.len() as f64;
        let my = ys.iter().sum::<f64>() / ys.len() as f64;
        let num: f64 = xs.iter().zip(&ys).map(|(x, y)| (x - mx) * (y - my)).sum();
        let den: f64 = xs.iter().map(|x| (x - mx).powi(2)).sum();
        let e = num / den;
        println!(
            "  {scheme:?}: spike RMS ~ (dt)^{e:.2} across {} time steps",
            points.len()
        );
        e
    });
    Verdict {
        energy_per_flip: energy,
        max_spike,
        exponent,
    }
}

#[test]
fn oscillating_plate_both_walls() {
    let ladder = std::env::var("RTX_E3_FALSIFIER_LADDER").is_ok();
    println!(
        "  body: {}",
        if circle_body() {
            "circle R 0.05"
        } else if stadium_body() {
            "stadium 0.35 x 0.02 (semicircular ends)"
        } else {
            "plate 0.35 x 0.02"
        }
    );
    let ghost = falsify(WallScheme::GhostBinary, ladder);
    let cut = falsify(WallScheme::CutCell, ladder);
    println!(
        "  energy per flipped column: ghost {:.3e}, cut {:.3e} (ratio {:.1}x); max spike: ghost {:.3e}, cut {:.3e} N/m",
        ghost.energy_per_flip,
        cut.energy_per_flip,
        ghost.energy_per_flip / cut.energy_per_flip.max(1e-300),
        ghost.max_spike,
        cut.max_spike
    );
    assert!(
        ghost.energy_per_flip > 0.0,
        "the binary wall must flip cells"
    );
}

/// The registered gates on the dt ladder.
#[test]
#[ignore = "item 11's gated ladder (dt, dt/2, dt/4 on both walls; tens of minutes on the host)"]
fn oscillating_plate_gates() {
    let ghost = falsify(WallScheme::GhostBinary, true);
    let cut = falsify(WallScheme::CutCell, true);
    let ratio = ghost.energy_per_flip / cut.energy_per_flip.max(1e-300);
    println!(
        "  GATES: ghost energy per flipped column {:.3e} ({:.2} of 2D), exponent {:.2}; cut energy {:.3e} ({:.1}x lower), max spike {:.3e} N/m ({:.2e} of ½ρU²L), exponent {:.2}",
        ghost.energy_per_flip,
        ghost.energy_per_flip / ENERGY_2D,
        ghost.exponent.unwrap(),
        cut.energy_per_flip,
        ratio,
        cut.max_spike,
        cut.max_spike / load_scale(),
        cut.exponent.unwrap()
    );
    let g2d = ghost.energy_per_flip / ENERGY_2D;
    assert!(
        (0.7..=1.3).contains(&g2d),
        "ghost energy per flip {g2d:.2} of 2D"
    );
    assert!(ratio >= 20.0, "cut energy only {ratio:.1}x lower");
    assert!(
        cut.max_spike < 0.05 * load_scale(),
        "cut max spike {:.3e}",
        cut.max_spike
    );
    let e = cut.exponent.unwrap();
    assert!((-0.3..=0.3).contains(&e), "cut exponent {e:.2}");
}