Reject zero Lorentz join columns#135
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isw_qflux_NA=1 with in_file_pert='none' assembles an identically zero non-axisymmetric source. That zero vector is the Arnoldi seed, so its normalization divides by zero (0/0 -> NaN) and zhseqr then fails to converge at every step, spinning without qflux output. Reject the configuration in check() with a clear message instead.
Add an optional right-hand side to the non-axisymmetric solve: the drive of a single-helicity perturbation given by a radial corrugation field (delta B^s/B_0^phi)_mn and an electrostatic potential harmonic Phi_mn. The vpar corrugation piece enters the A1/A2 force channels with velocity weights a3m and x^2 (sigma-odd), the ExB piece with weights x^-1 and a1m (sigma-even); the two new velocity moments are computed in compute_sources. Input via new &ntv_input variables (isw_hel_drive, m_theta_hel, hel_brad_re/im, hel_phim_re/im), default off. Band profiles, moments and dimensional prefactors follow a CAS-checked derivation (see issue #118). Off by default: golden-record QL summary.h5 is reproduced to 1e-15 against a main build.
Review findings on the drive commit: fold the x^(3k-4) weight into a single power so the x=0 quadrature node stays finite; skip the moment quadrature on the precomputed-matrix-element path and reject isw_hel_drive at run time when the moments are unavailable; reject the unvalidated relativistic branch, reconstruction mode and unset species data; deallocate asource_hel in collop_unload.
The zero-source guard added upstream rejects isw_qflux_NA=1 with in_file_pert='none'. With the misalignment drive, that configuration is valid: the drive supplies the non-axisymmetric source. Relax the guard so it fires only when the drive is off or all its amplitudes are zero.
This was referenced Jul 11, 2026
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Summary
Stack dependency: #133 at
03f5b9dacdbf7c882fac01c37972e8e266575351. This PR remains pointed atmainand must not merge before its dependency.For every nonzero finite column, the existing normalization and column-sum-one conservation law are unchanged. The patch does not choose a physical replacement for a zero column and does not change join algebra, linear solves, discretization, tolerances, array layout, ABI, or generated nonzero values. It converts an undefined
0/0into an exact diagnostic rejection. The upstream meaning of the zero column remains tracked in #134.Verification
Failing before (
03f5b9d), exact HELCORE source-only replay with IEEE-invalid trapping:Passing diagnostic after (
6e30459):The same trapped replay now reports:
It exits without SIGFPE, IEEE invalid, NaN,
zhseqr, or DGBSV failure. This is a diagnostic safety result, not a valid transport calculation; partial qflux files are rejected.