- the tangent scatter runs per CSR entry over a transposed contribution
map, in the serial scatter's order (same bits), on rayon;
- large fronts' trailing gemms run per column block on rayon;
- forward solve multifrontal, backward top-down, subtrees on rayon;
- total_lagrangian::internal_force: the force of internal_force_and_tangent
alone (bit-identical, tested), used by modified-Newton iterations that
reuse the factor; the tangent is evaluated only when a refresh is due.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
rtx_fea::solvers::SparseLdlt: nested-dissection ordering, etree,
fundamental supernodes, multifrontal numeric factorisation (blocked
LDLt, matrixmultiply gemm, rayon over subtrees, bit-deterministic at
any thread count), symbolic analysis reused while the pattern holds.
NonlinearDynamicStepper: TangentSolver::{BandedLu (default, unchanged
float for float), SparseLdlt { reuse }} via with_tangent_solver or
RTX_FEA_TANGENT=sparse[:K]; fixed-pattern CSR assembled from parallel
element evaluations (forces summed in the banded path's order);
optional modified Newton (factor reuse). The per-element kernel is
factored out of assemble() unchanged.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
