Lifts the 27 `#[ignore]` markers on rtx-cfd and rtx-fea. 21 of them fail;
6 were stale, marking components that have since been implemented. The
suite now reports the truth, which means it is red.
The eigensolver had three independent defects, each individually fatal.
Found by writing closed-form tests first and confirming red:
- The generalized reduction formed M^-1 K and ran Lanczos on it.
M^-1 K has the right eigenvalues but is not symmetric even when K
and M both are, and Lanczos assumes symmetry -- so it returned a
wrong answer rather than an inaccurate one. On a 2-DOF spring-mass
chain with M = diag(2,1) it gave 1.633 against an exact root of
1 - sqrt(2)/2 ~= 0.293. Replaced with the Cholesky reduction
B = L^-1 (K - sigma M) L^-T.
- Output was unsorted. nalgebra's symmetric_eigen gives no ordering
guarantee and none was imposed; modal analysis names modes by index,
so the ordering is part of the contract.
- Eigenvectors could not be transformed back out of the Krylov basis.
The Lanczos block was (n x num_iter) and the tridiagonal
eigenvectors (min(num_iter, k) x k); whenever those differed the
multiply panicked on a dimension mismatch -- that is, on every
problem with more DOFs than requested modes, which is every real
modal analysis.
Lanczos now runs shift-invert by default. Plain Lanczos converges to the
eigenvalues of largest magnitude and modal analysis wants the lowest, so
without it the solver returns the modes nobody asked for. Also switched
to full reorthogonalization, twice per step, so converged eigenvalues do
not reappear as ghosts indistinguishable from genuine repeated roots.
ModalResults computed f = sqrt(lambda / 2pi) instead of
sqrt(lambda) / 2pi. The two agree only at lambda = 2pi, so a smoke test
asserting a positive frequency would never separate them. A
`#[cfg(disabled)]` module in the same file asserted the correct formula
-- the module was disabled rather than the bug fixed. That module is
removed; tests/eigenvalue_closed_form.rs supersedes it with every
expected value derived analytically.
Corrected a fixture rather than loosening its tolerance:
implementation_tests expected the smallest eigenvalue of
tridiag(-1, 4, -1) at order 3 to be 4 - 2 sqrt(2) ~= 1.172. The
eigenvalues of tridiag(c, a, c) are a + 2c cos(k pi / (n+1)), so the
true value is 4 - sqrt(2) ~= 2.586. The test had been quarantined for
failing to match an expectation that was never right.
rtx-fsi is untouched and stays 26/26.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
rtx-cfd (18,715 lines) and rtx-fea (36,576 lines) both exist and nothing
connects them -- rtx-fea is commented out of rtx-cfd's dependencies. This
is the coupling layer, and it is the piece Prof. Charbel Farhat's 2026
Guggenheim Medal citation is actually about.
It depends on NEITHER solver. The properties that make a partitioned
coupling correct -- conservation of force, moment and interface work --
are statements about the transfer operators alone, so they can be
validated now, on solvers whose canonical-benchmark validation is still
outstanding. Adapters to the concrete solvers belong above this.
TRANSFER (transfer.rs). Weights satisfy two constraints:
sum(w_i) = 1 partition of unity -> force conserved
sum(w_i x_i) = x_face linear reproduction -> MOMENT conserved
The second is the one that gets skipped. Inverse-distance weighting
satisfies the first and generally violates the second, conserving force
while corrupting moment -- which shows up as slow spurious rotation rather
than as an obvious error. Underdetermined for >4 nodes, so it takes the
minimum-norm solution w = A^T (A A^T)^+ b.
That is a PSEUDO-inverse, and not for defensiveness. A wetted surface is a
surface, so its nodes are usually planar, and for a planar patch the z
constraint row is an affine multiple of the ones row -- A A^T is genuinely
rank-deficient. The constraint is redundant there, not unsatisfiable. An
ordinary inverse rejects the most ordinary interface there is; I found
this because my first test fixture was collinear and the code correctly
refused it. Constraints are then verified against the weights actually
obtained, since a pseudo-inverse returns a least-squares answer whether or
not the system was consistent.
Motion transfer uses the TRANSPOSE of the load operator, which makes
interface work conserved identically: (Hf).v = f.(H^T v). Any other
pairing leaks energy every step, and the leak looks like physics until it
destabilises.
COUPLING (coupling.rs). Staggered and Aitken-relaxed subiteration. The
decisive tests reproduce the added-mass effect: at a gain of 2.5 the
fixed-relaxation scheme DIVERGES and is reported as CouplingDiverged
rather than as an exhausted budget, and Aitken recovers the same case. A
partitioned coupling that cannot reproduce its own classic failure mode is
not being tested hard enough. Aitken is exact for a linear fixed point, so
convergence is asserted at <=4 iterations -- pinning that this is the real
delta-squared formula and not an under-relaxation that happens to work.
SCOPE, stated up front in the crate docs: small-displacement transpiration
coupling on a fixed mesh. Deliberately not ALE and not embedded-boundary,
so the Discrete Geometric Conservation Law does not yet apply -- the mesh
does not move. Large motion needs an embedded boundary treatment; that is
the next phase, not an oversight.
External comparator named at entry: Turek-Hron FSI2/FSI3, not yet reached.
26 tests written red-first; cargo test/fmt/clippy -D warnings clean.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Whole-workspace rustfmt pass picked up while iterating on Mamba GPU
backward work. Verified formatting-only via diff sampling; no logic
changed.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
Declared but never referenced; forced openblas-build (no good Apple-Silicon
backend) and broke the macOS build.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
The workspace root was upgraded to thiserror = "2" in an earlier commit,
but 56 per-crate Cargo.toml files still independently declared "1.0".
These crates do not use workspace.dependencies inheritance for thiserror.
All updated to thiserror = "2" for complete fleet alignment.
Includes: rtx-backend, rtx-tensor, rtx-losses, rtx-backend-cuda/rocm/metal,
all training crates (rtx-auto, rtx-rl, rtx-distributed, rtx-federated, etc.),
specialized crates (rtx-science, rtx-platform, rtx-nmf, rtx-neuro-*),
production crates (rtx-streaming, rtx-serving-api), and all demo crates.
cargo check --workspace: PASSES.
