KF/PE - BUGFIX! - Self-consistent xi_s for the NTV kernel input; static scheduling for the kinetic kernel loop

[logan-nc]

Stacked on #422 (feature/kinetic-resonance-knots). The overnight resolution of the PE-vs-NTV torque discrepancy (issue #423's measured motivation; RESULTS.md §34–§35).

The bug

In kinetic runs, the Clebsch ξ^α fed to the NTV kernel (via dbob_m/divx_m) was re-solved from the ideal A, B, C matrices — inconsistent with the self-consistent kinetic tangential response exactly where resonant layers live. Fortran (gpeq.f, kin_flag) instead scales the stored self-consistent ξ_s by the singfac regularization factor and inverts nothing. This is the same physics flaw #407 fixes on the MatrixSplines branch (there: a silently broken Cholesky of the non-Hermitian kinetic A; here: a valid Cholesky of the wrong — ideal — A).

The consequence (measured, DIII-D kinetic-calculated full chain)

The perturbative NTV evaluation was driven by a tangential displacement that ignores the kinetic layer response, producing a phantom 4× torque concentrated in a ~2e-3-wide resonant core at the pedestal ω_E crossing (fgar: 0.7241 N·m, of which +0.622 in ψ∈[0.90, 0.95]; the self-consistent EL solution collects 0.046 there — and the EL side was verified faithful at every level: boundary ≡ volume torque to 7 digits, FKG assembly and kinetic RHS sign-by-sign Fortran-conformant per fortran-physics-reviewer, matrix-spline resolution and integrator step size both exonerated by direct null experiments).

With the fix, the phantom collapses (+0.622 → +0.033) and the two independent torque calculations agree band-by-band (resonant layer: 0.0461 vs 0.0455). Domain-matched totals (ΔIm over [ψ_c, psilim] — fgar's exact domain; the sub-ψ_c Im(u1†u2) offset is non-dissipative initial-condition content, ±0.05 with opposite signs across cases):

case (deterministic, post-:static)	PE (domain-matched)	fgar	agreement
rot factor 0.2, reg_spot 0.05	0.1456	0.1460	0.3%
rot factor 1.0, reg_spot 0.05	0.1322	0.1655	20%
rot factor 1.0, reg_spot 0.01	0.1322	0.1397	5.4%

Where the comparison is regularization-unambiguous (rot=0.2: resonances away from rationals), the two independent torque calculations now agree to 0.3%. The rot=1.0 residual sits inside fgar's own reg_spot sensitivity band (its answer moves 18% between reg 0.05 and 0.01 — the acknowledged near-rational input ambiguity, present in Fortran too); PE is reg-independent by construction.

Second fix in this PR: determinism

CalculatedKineticMatrices.jl's per-surface kernel loop was the only threaded loop in the codebase using Threads.@threads without :static while indexing per-thread scratch by threadid() — dynamic-scheduling task migration corrupts kinetic matrix rows at rare-migration frequency. Observed live: three runs of one identical deck gave et[1] = 1.0053 / 1.1355 / 0.9895. With :static, identical decks reproduce bit-identically (verified), and et returns exactly to the pre-fix value — every historical calculated-kinetic result carries this latent race.

Effects on outputs: kinetic-run regularized quantities (xi_clebsch_alpha, *_reg fields) and every NTV torque driven by them change; ideal runs and reg_spot = 0 are bit-unaffected. Kinetic harness cases will move — new baselines with this physics justification.

Review items

• Kinetic-ness is currently detected via populated kwmats splines (sentinel = 5 knots); reviewers may prefer threading an explicit flag from kinetic_factor > 0 — noted as the clean alternative.
• The domain-matched comparison rule (and the eventual gpout_dw ψ-profile port, issue Port gpout_dw / gpout_dw_matrix (psi-resolved torque response profiles and matrices) as the grid-logic diagnostic #423) is where the "which torque is which" delineation (PerturbedEquilibrium - DOCS - Delineate the boundary-response torque from the KineticForces NTV torque #424) completes.

⚠️ REQUIRES THIRD-PARTY HUMAN REVIEW BEFORE MERGING — NON-NEGOTIABLE. DO NOT MERGE WITHOUT AN APPROVING HUMAN REVIEW.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LzbLFQKyuRE5DYZmLokKmk

[logan-nc]

Closing without merging — both halves are superseded, and one of my claims here needs correcting.

1. The :static fix is already on develop. Commit 9fe8a60c9 ("KineticForces - IMPROVEMENT - :static kinetic-matrix threading + typed species + shared constants") added exactly this scheduling fix, with the same reasoning in its comment. It landed after this stack forked (our fork point 9491f893d is dated 2026-08-16), so this branch never had it — which is why the nondeterminism was observable here.

Correction to this PR's description: it claimed "every historical calculated-kinetic run carries this latent race." That is wrong as written. The race is real and was real on this stack, but develop has been fixed since 9fe8a60c9; only runs on branches forked before it (like this one) are affected. The observed scatter — et[1] = 1.0053 / 1.1355 / 0.9895 on identical decks — was a symptom of the stack being behind develop, not of a live defect in develop.

2. The ξ_s self-consistency fix is owned by #407. Same file, same function, same physics (kinetic runs must regularize the stored self-consistent ξ_s rather than re-solve it from the ideal matrices, mirroring Fortran gpeq.f kin_flag). #407 is based on develop, already reviewed, and additionally adds [ForcingTerms]/[PerturbedEquilibrium] to Solovev_kinetic_calculated_example plus tracked harness quantities — the coverage this branch lacked. No reason to ask anyone to reconcile two versions of one fix.

Worth flagging for #407 and #414 reviewers: #414 forces reg_spot = 0 in self-consistent kinetic runs, and compute_clebsch_displacements early-returns when reg_spot == 0 before the kinetic branch. So once #414 lands, the kinetic branch #407 fixes is unreachable on that path — still correct, still the right safety net if regularization is ever re-enabled, but no longer load-bearing. The physics evidence for turning regularization off is in #414 and in handoff/issue376/RESULTS.md §36–§37.

The measurement this PR produced still stands and is recorded in #414: with regularization off, the NTV torque and the Euler–Lagrange solution's own dissipation agree to 0.15% (0.1324 vs 0.1322 N·m) on the DIII-D kinetic-calculated case.

Branch bugfix/kinetic-clebsch-xi-s is left in place for the record.