embedded3 item 10b: virtual merging of small cells in the projection (fraction < 0.1 → master = largest active face neighbour; off-stencil links on the fine Poisson level; merged rhs, anchor, mass residual and source scale); static sphere rows within 0.02 %, loads 9.4/10.4 %; stadium falsifier spikes 39–54× below the binary wall (circle 6–8×), energy per event 6–9× lower

Co-Authored-By: Claude Fable 5.1 <[email protected]>

crates/specialized/rtx-cfd/tests/embedded3_sphere/mod.rs

@@ -197,11 +197,14 @@ pub fn measure(n: usize, scheme: WallScheme, c: (f64, f64, f64)) -> Measurement
     let body = solver.body().expect("body");
     let t = solver.time();
     // The apertured divergence per unit volume, the porous surface's flux
-    // through the wall included (the plain divergence on the binary wall).
+    // through the wall included (the plain divergence on the binary wall);
+    // a virtually merged small cell's flux counts with its master's (only
+    // the pair's continuity holds).
     let mut max_div = 0.0_f64;
     let mut at_vol = 1.0;
     let mut sum_flux = 0.0;
     let (wall_fluxes, _) = mask.wall_flux_table(body, t);
+    let mut cell_flux = vec![0.0; g.cells()];
     for k in 0..n {
         for j in 0..n {
             for i in 0..n {
@@ -220,15 +223,18 @@ pub fn measure(n: usize, scheme: WallScheme, c: (f64, f64, f64)) -> Measurement
                             * h
                             * h
                         + wall_fluxes[idx];
-                    sum_flux += flux.abs();
-                    if (flux / (h * h * h)).abs() > max_div {
-                        max_div = (flux / (h * h * h)).abs();
-                        at_vol = mask.vol(idx);
-                    }
+                    cell_flux[mask.master(idx).unwrap_or(idx)] += flux;
                 }
             }
         }
     }
+    for (idx, &flux) in cell_flux.iter().enumerate() {
+        sum_flux += flux.abs();
+        if (flux / (h * h * h)).abs() > max_div {
+            max_div = (flux / (h * h * h)).abs();
+            at_vol = mask.vol(idx);
+        }
+    }
     println!(
         "    [{scheme:?} n {n}] max div {max_div:.2e} in a cell of fluid fraction {at_vol:.3e}; Σ|flux| {sum_flux:.2e}; last step residual {:.2e}",
         last.final_residual