R7 phase 1: host prototype of the composite Poisson with one nested ratio-2 patch (embedded3::composite; three coarse-fine fluxes, FAC-preconditioned BiCGStab; P1/P1b/P2/P3 gates as ignored tests). Additive module, nothing calls it.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
This commit is contained in:
Omar Sobh
2026-09-25 17:53:50 -05:00
co-authored by Claude Opus 5.5
parent d63806c0e6
commit e19cad03b2
5 changed files with 1458 additions and 0 deletions
@@ -0,0 +1,640 @@
//! R7 phase 1: the composite Poisson problem with one nested ratio-2 patch
//! (`embedded3::composite`, a host prototype nothing else calls).
//!
//! - P1 (`composite_mms_ladder`, ignored): manufactured solution on the unit
//! cube, patch = the middle half, n = 16/32/64 coarse; errors split into
//! the interface cells (owners of a coarse–fine face), the rest of the
//! patch, and the rest of the coarse grid, for the three interface fluxes
//! and the uniform coarse / fine grids;
//! - P2 (`composite_cut_sphere`, ignored): a Neumann sphere inside the patch
//! cut by embedded3's `CutGeometry` on the fine level, against the
//! uniformly fine grid with the same cut;
//! - P3 (`composite_cost`, ignored): unknowns and wall time against the
//! uniformly fine grid solved by embedded3's production PCG.
//!
//! Output CSVs go to `$R7_OUT` when set. The default (non-ignored) test is a
//! seconds-scale smoke of the assembly and the solve.
use rtx_cfd::solvers::incompressible::MultigridParameters;
use rtx_cfd::solvers::incompressible::embedded3::Grid;
use rtx_cfd::solvers::incompressible::embedded3::composite::{
Composite, CompositeSpec, Interface, Sdf, solve_bicgstab, uniform_problem,
};
use rtx_cfd::solvers::incompressible::embedded3::poisson::solve_pcg;
use std::f64::consts::PI;
use std::io::Write;
use std::sync::Arc;
fn mms_u(x: f64, y: f64, z: f64) -> f64 {
(1.3 * PI * x + 0.2).cos() * (1.1 * PI * y + 0.4).cos() * (0.9 * PI * z + 0.6).cos()
}
fn mms_f(x: f64, y: f64, z: f64) -> f64 {
PI * PI * (1.69 + 1.21 + 0.81) * mms_u(x, y, z)
}
/// A localized feature inside the patch on top of the smooth field: the
/// case local refinement is for (a Gaussian of width 0.06 at the centre).
const BUMP_S: f64 = 0.06;
fn bump_u(x: f64, y: f64, z: f64) -> f64 {
let r2 = (x - 0.5).powi(2) + (y - 0.5).powi(2) + (z - 0.5).powi(2);
mms_u(x, y, z) + (-r2 / (BUMP_S * BUMP_S)).exp()
}
fn bump_f(x: f64, y: f64, z: f64) -> f64 {
let r2 = (x - 0.5).powi(2) + (y - 0.5).powi(2) + (z - 0.5).powi(2);
let s2 = BUMP_S * BUMP_S;
mms_f(x, y, z) - (4.0 * r2 / (s2 * s2) - 6.0 / s2) * (-r2 / s2).exp()
}
const SPH_C: [f64; 3] = [0.52, 0.49, 0.51];
const SPH_R: f64 = 0.12;
const SPH_A: f64 = 2.0 * PI;
fn sph_r(x: f64, y: f64, z: f64) -> f64 {
((x - SPH_C[0]).powi(2) + (y - SPH_C[1]).powi(2) + (z - SPH_C[2]).powi(2)).sqrt()
}
/// `cos(a (r − R))`: zero normal derivative on the sphere.
fn sph_u(x: f64, y: f64, z: f64) -> f64 {
(SPH_A * (sph_r(x, y, z) - SPH_R)).cos()
}
fn sph_f(x: f64, y: f64, z: f64) -> f64 {
let r = sph_r(x, y, z);
let q = SPH_A * (r - SPH_R);
SPH_A * SPH_A * q.cos() + 2.0 * SPH_A * q.sin() / r
}
fn sphere() -> Sdf {
Arc::new(|x, y, z| sph_r(x, y, z) - SPH_R)
}
/// Volume-weighted RMS and max of the error over a subset.
#[derive(Default, Clone, Copy)]
struct Err {
s2: f64,
vol: f64,
max: f64,
count: usize,
}
impl Err {
fn add(&mut self, e: f64, v: f64) {
self.s2 += e * e * v;
self.vol += v;
self.max = self.max.max(e.abs());
self.count += 1;
}
fn l2(&self) -> f64 {
if self.vol > 0.0 {
(self.s2 / self.vol).sqrt()
} else {
f64::NAN
}
}
}
fn out_file(name: &str) -> Option<std::fs::File> {
let dir = std::env::var("R7_OUT").ok()?;
std::fs::create_dir_all(&dir).ok()?;
std::fs::File::create(format!("{dir}/{name}")).ok()
}
struct CompositeRun {
unknowns: usize,
fine_unknowns: usize,
iterations: usize,
rel: f64,
setup_s: f64,
solve_s: f64,
asym: f64,
/// interface, patch interior (fine, not interface), coarse (not
/// interface), cut cells, all.
err: [Err; 5],
}
fn run_composite(
n: usize,
lo: usize,
hi: usize,
iface: Interface,
body: Option<Sdf>,
exact: fn(f64, f64, f64) -> f64,
source: fn(f64, f64, f64) -> f64,
measure_asym: bool,
) -> CompositeRun {
let g = Grid::cubic(n, n, n, 1.0 / n as f64);
let spec = CompositeSpec {
coarse: g,
lo: [lo; 3],
hi: [hi; 3],
interface: iface,
body,
source: &source,
dirichlet: &exact,
};
let t = std::time::Instant::now();
let c = Composite::build(&spec);
let build_s = t.elapsed().as_secs_f64();
let mut x = vec![0.0; c.unknowns()];
let st = solve_bicgstab(&c, &mut x, 1e-11, 400, 2);
assert!(st.converged, "composite solve did not converge: {st:?}");
let mut err = [Err::default(); 5];
for u in 0..c.unknowns() {
let p = c.centre[u];
let e = x[u] - exact(p[0], p[1], p[2]);
let v = c.volume[u];
let fine = u >= c.n_coarse;
let class = if c.at_interface[u] {
0
} else if fine {
1
} else {
2
};
err[class].add(e, v);
if c.cut[u] {
err[3].add(e, v);
}
err[4].add(e, v);
}
CompositeRun {
unknowns: c.unknowns(),
fine_unknowns: c.unknowns() - c.n_coarse,
iterations: st.iterations,
rel: st.rel_residual,
setup_s: build_s + st.setup_s,
solve_s: st.solve_s,
asym: if measure_asym {
c.a.asymmetry()
} else {
f64::NAN
},
err,
}
}
struct UniformRun {
cells: usize,
iterations: usize,
setup_s: f64,
solve_s: f64,
/// inside the patch region [lo, hi)·h_c, outside it, cut cells, all.
err: [Err; 4],
}
fn run_uniform(
n: usize,
region: (f64, f64),
body: Option<&Sdf>,
exact: fn(f64, f64, f64) -> f64,
source: fn(f64, f64, f64) -> f64,
) -> UniformRun {
let g = Grid::cubic(n, n, n, 1.0 / n as f64);
let t = std::time::Instant::now();
let (prob, frac) = uniform_problem(g, body, &source, &exact);
let build_s = t.elapsed().as_secs_f64();
let mut p = vec![0.0; g.cells()];
let l1: f64 = prob.rhs.iter().map(|v| v.abs()).sum();
let params = MultigridParameters {
max_iterations: 2000,
..MultigridParameters::default()
};
let sol = solve_pcg(&prob, &mut p, &params, 1e-11 * l1, None);
assert!(sol.converged, "uniform solve did not converge");
let h = g.dx;
let mut err = [Err::default(); 4];
for k in 0..n {
for j in 0..n {
for i in 0..n {
let idx = g.cell(k, j, i);
if !prob.active[idx] {
continue;
}
let x = [
(i as f64 + 0.5) * h,
(j as f64 + 0.5) * h,
(k as f64 + 0.5) * h,
];
let e = p[idx] - exact(x[0], x[1], x[2]);
let v = frac[idx] * h * h * h;
let inside = x.iter().all(|&c| c > region.0 && c < region.1);
err[usize::from(!inside)].add(e, v);
if frac[idx] < 1.0 {
err[2].add(e, v);
}
err[3].add(e, v);
}
}
}
UniformRun {
cells: prob.active.iter().filter(|&&a| a).count(),
iterations: sol.iterations,
setup_s: build_s + sol.setup_ns as f64 * 1e-9,
solve_s: sol.iterate_ns as f64 * 1e-9,
err,
}
}
fn order(a: f64, b: f64) -> f64 {
(a / b).log2()
}
#[test]
fn composite_smoke() {
for iface in [Interface::Direct, Interface::Octree, Interface::Quadratic] {
let r = run_composite(12, 3, 9, iface, None, mms_u, mms_f, true);
eprintln!(
"{iface:?}: {} unknowns, {} it, rel {:.2e}, asym {:.2e}, L2 iface {:.3e} all {:.3e}",
r.unknowns,
r.iterations,
r.rel,
r.asym,
r.err[0].l2(),
r.err[4].l2()
);
assert!(r.err[4].l2() < 5e-3);
if iface == Interface::Direct {
assert!(r.asym < 1e-14);
}
}
}
#[test]
#[ignore = "P1 ladder (minutes)"]
fn composite_mms_ladder() {
ladder("p1_mms.csv", mms_u, mms_f);
}
#[test]
#[ignore = "P1b ladder with a localized bump (minutes)"]
fn composite_bump_ladder() {
ladder("p1b_bump.csv", bump_u, bump_f);
}
fn ladder(name: &str, exact: fn(f64, f64, f64) -> f64, source: fn(f64, f64, f64) -> f64) {
let mut csv = out_file(name);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"scheme,n,unknowns,iters,rel,l2_iface,linf_iface,l2_patch,linf_patch,l2_coarse,linf_coarse,l2_all,linf_all,setup_s,solve_s"
)
.ok();
}
let ns = [16usize, 32, 64];
let mut table: Vec<(String, Vec<[f64; 8]>)> = Vec::new();
for iface in [Interface::Direct, Interface::Octree, Interface::Quadratic] {
let mut rows = Vec::new();
for &n in &ns {
let r = run_composite(n, n / 4, 3 * n / 4, iface, None, exact, source, false);
let e = r.err;
eprintln!(
"{iface:?} n {n}: {} unk, {} it, rel {:.1e}; iface L2 {:.3e} Linf {:.3e} | patch L2 {:.3e} Linf {:.3e} | coarse L2 {:.3e} Linf {:.3e} | all L2 {:.3e} | {:.2}+{:.2} s",
r.unknowns,
r.iterations,
r.rel,
e[0].l2(),
e[0].max,
e[1].l2(),
e[1].max,
e[2].l2(),
e[2].max,
e[4].l2(),
r.setup_s,
r.solve_s
);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"{iface:?},{n},{},{},{:.3e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.3},{:.3}",
r.unknowns,
r.iterations,
r.rel,
e[0].l2(),
e[0].max,
e[1].l2(),
e[1].max,
e[2].l2(),
e[2].max,
e[4].l2(),
e[4].max,
r.setup_s,
r.solve_s
)
.ok();
}
rows.push([
e[0].l2(),
e[0].max,
e[1].l2(),
e[1].max,
e[2].l2(),
e[2].max,
e[4].l2(),
e[4].max,
]);
}
table.push((format!("{iface:?}"), rows));
}
for (label, n_of) in [("uniform-coarse", 1usize), ("uniform-fine", 2)] {
for &n in &ns {
let r = run_uniform(n_of * n, (0.25, 0.75), None, exact, source);
let e = r.err;
eprintln!(
"{label} n {}: {} cells, {} it; patch-region L2 {:.3e} Linf {:.3e} | outside L2 {:.3e} Linf {:.3e} | all L2 {:.3e} | {:.2}+{:.2} s",
n_of * n,
r.cells,
r.iterations,
e[0].l2(),
e[0].max,
e[1].l2(),
e[1].max,
e[3].l2(),
r.setup_s,
r.solve_s
);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"{label},{},{},{},0,nan,nan,{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.3},{:.3}",
n_of * n,
r.cells,
r.iterations,
e[0].l2(),
e[0].max,
e[1].l2(),
e[1].max,
e[3].l2(),
e[3].max,
r.setup_s,
r.solve_s
)
.ok();
}
}
}
eprintln!("orders (16→32, 32→64): iface L2 / Linf | patch L2 | coarse L2 | all L2 / Linf");
for (label, rows) in &table {
let o = |c: usize| (order(rows[0][c], rows[1][c]), order(rows[1][c], rows[2][c]));
eprintln!(
"{label}: iface {:.2},{:.2} / {:.2},{:.2} | patch {:.2},{:.2} | coarse {:.2},{:.2} | all {:.2},{:.2} / {:.2},{:.2}",
o(0).0,
o(0).1,
o(1).0,
o(1).1,
o(2).0,
o(2).1,
o(4).0,
o(4).1,
o(6).0,
o(6).1,
o(7).0,
o(7).1
);
}
}
#[test]
#[ignore = "P2 cut sphere in the patch (minutes)"]
fn composite_cut_sphere() {
let mut csv = out_file("p2_sphere.csv");
if let Some(f) = csv.as_mut() {
writeln!(
f,
"scheme,n,unknowns,iters,l2_iface,linf_iface,l2_patch,linf_patch,l2_coarse,l2_cut,linf_cut,l2_all,linf_all"
)
.ok();
}
let body = sphere();
for &n in &[16usize, 32, 64] {
for iface in [Interface::Direct, Interface::Octree, Interface::Quadratic] {
let r = run_composite(
n,
n / 4,
3 * n / 4,
iface,
Some(body.clone()),
sph_u,
sph_f,
false,
);
let e = r.err;
eprintln!(
"{iface:?} n {n}: {} unk ({} fine), {} it; iface L2 {:.3e} | patch L2 {:.3e} Linf {:.3e} | coarse L2 {:.3e} | cut L2 {:.3e} Linf {:.3e} | all L2 {:.3e} Linf {:.3e}",
r.unknowns,
r.fine_unknowns,
r.iterations,
e[0].l2(),
e[1].l2(),
e[1].max,
e[2].l2(),
e[3].l2(),
e[3].max,
e[4].l2(),
e[4].max
);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"{iface:?},{n},{},{},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e}",
r.unknowns,
r.iterations,
e[0].l2(),
e[0].max,
e[1].l2(),
e[1].max,
e[2].l2(),
e[3].l2(),
e[3].max,
e[4].l2(),
e[4].max
)
.ok();
}
}
for (label, m) in [("uniform-coarse", n), ("uniform-fine", 2 * n)] {
let r = run_uniform(m, (0.25, 0.75), Some(&body), sph_u, sph_f);
let e = r.err;
eprintln!(
"{label} n {m}: {} cells, {} it; patch-region L2 {:.3e} Linf {:.3e} | outside L2 {:.3e} | cut L2 {:.3e} Linf {:.3e} | all L2 {:.3e} Linf {:.3e}",
r.cells,
r.iterations,
e[0].l2(),
e[0].max,
e[1].l2(),
e[2].l2(),
e[2].max,
e[3].l2(),
e[3].max
);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"{label},{m},{},{},nan,nan,{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e},{:.6e}",
r.cells,
r.iterations,
e[0].l2(),
e[0].max,
e[1].l2(),
e[2].l2(),
e[2].max,
e[3].l2(),
e[3].max
)
.ok();
}
}
}
}
#[test]
#[ignore = "P3 cost against the uniformly fine grid (minutes)"]
fn composite_cost() {
let mut csv = out_file("p3_cost.csv");
if let Some(f) = csv.as_mut() {
writeln!(
f,
"field,case,n,patch,unknowns,iters,setup_s,solve_s,l2_patch_region,linf_patch_region,l2_all"
)
.ok();
}
let n = 64usize;
let h = 1.0 / n as f64;
type Pair = (
&'static str,
fn(f64, f64, f64) -> f64,
fn(f64, f64, f64) -> f64,
);
let fields: [Pair; 2] = [("smooth", mms_u, mms_f), ("bump", bump_u, bump_f)];
for (field, exact, source) in fields {
for (label, lo, hi) in [("half", 16usize, 48usize), ("quarter", 24, 40)] {
let r = run_composite(n, lo, hi, Interface::Quadratic, None, exact, source, false);
// The patch region's error: interface fine cells + patch interior.
let mut e = Err::default();
let c = {
let g = Grid::cubic(n, n, n, h);
let spec = CompositeSpec {
coarse: g,
lo: [lo; 3],
hi: [hi; 3],
interface: Interface::Quadratic,
body: None,
source: &source,
dirichlet: &exact,
};
Composite::build(&spec)
};
let mut x = vec![0.0; c.unknowns()];
let _ = solve_bicgstab(&c, &mut x, 1e-11, 400, 2);
for u in c.n_coarse..c.unknowns() {
let p = c.centre[u];
e.add(x[u] - exact(p[0], p[1], p[2]), c.volume[u]);
}
eprintln!(
"{field} composite {label} (n {n}, patch {lo}..{hi}): {} unknowns, {} it, setup {:.2} s, solve {:.2} s, patch L2 {:.3e} Linf {:.3e}, all L2 {:.3e}",
r.unknowns,
r.iterations,
r.setup_s,
r.solve_s,
e.l2(),
e.max,
r.err[4].l2()
);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"{field},composite-{label},{n},{lo}..{hi},{},{},{:.3},{:.3},{:.6e},{:.6e},{:.6e}",
r.unknowns,
r.iterations,
r.setup_s,
r.solve_s,
e.l2(),
e.max,
r.err[4].l2()
)
.ok();
}
for (ulabel, m) in [("uniform-fine", 2 * n), ("uniform-coarse", n)] {
let r = run_uniform(m, (lo as f64 * h, hi as f64 * h), None, exact, source);
eprintln!(
"{field} {ulabel} n {m} (region {lo}..{hi}): {} cells, {} it, setup {:.2} s, solve {:.2} s, region L2 {:.3e} Linf {:.3e}, all L2 {:.3e}",
r.cells,
r.iterations,
r.setup_s,
r.solve_s,
r.err[0].l2(),
r.err[0].max,
r.err[3].l2()
);
if let Some(f) = csv.as_mut() {
writeln!(
f,
"{field},{ulabel},{m},{lo}..{hi},{},{},{:.3},{:.3},{:.6e},{:.6e},{:.6e}",
r.cells,
r.iterations,
r.setup_s,
r.solve_s,
r.err[0].l2(),
r.err[0].max,
r.err[3].l2()
)
.ok();
}
}
}
}
}
fn quad_u(x: f64, y: f64, z: f64) -> f64 {
x * x + 2.0 * y * y - 1.5 * z * z + 0.7 * x * y - 0.4 * y * z + 0.9 * x * z + 0.3 * x
}
fn quad_f(_x: f64, _y: f64, _z: f64) -> f64 {
-(2.0 + 4.0 - 3.0)
}
/// Local consistency: the exact quadratic's residual on the rows away from
/// the outer boundary, per interface flux (the Quadratic ghost is exact for
/// quadratics, so its interface rows must be at round-off).
#[test]
fn composite_quadratic_consistency() {
let n = 12;
let g = Grid::cubic(n, n, n, 1.0 / n as f64);
for iface in [Interface::Direct, Interface::Octree, Interface::Quadratic] {
let spec = CompositeSpec {
coarse: g,
lo: [3; 3],
hi: [9; 3],
interface: iface,
body: None,
source: &quad_f,
dirichlet: &quad_u,
};
let c = Composite::build(&spec);
let u: Vec<f64> = c.centre.iter().map(|p| quad_u(p[0], p[1], p[2])).collect();
let mut au = vec![0.0; u.len()];
c.a.apply(&u, &mut au);
let h = g.dx;
let (mut m_if, mut m_in) = (0.0f64, 0.0f64);
for r in 0..u.len() {
let p = c.centre[r];
if p.iter().any(|&x| x < h || x > 1.0 - h) {
continue;
}
// Relative to the row's volume source |f| V.
let res = (c.rhs[r] - au[r]).abs() / (3.0 * c.volume[r]);
if c.at_interface[r] {
m_if = m_if.max(res);
} else {
m_in = m_in.max(res);
}
}
eprintln!("{iface:?}: max |truncation| / |f V|: interface {m_if:.3e}, interior {m_in:.3e}");
assert!(m_in < 1e-10);
if iface == Interface::Quadratic {
assert!(m_if < 1e-10, "quadratic ghost not exact on a quadratic");
}
}
}