Solvers and backends

The route and element combination determine which backend is appropriate. Method names alone are not convergence guarantees; inspect the residual, conditioning and final diagnostics for every calculation.

Analysis	Public status	Available methods or backend
Linear static	QUALIFIED_BOUNDED	Direct and iterative sparse routes within the element matrix.
Modal	SUPPORTED_WITH_LIMITATIONS	Sparse eigenvalue routes for the recorded bounded cases.
Newmark / harmonic	SUPPORTED_WITH_LIMITATIONS	Controlled linear routes with documented mass and damping assumptions.
Linear buckling	SUPPORTED_WITH_LIMITATIONS	Bounded sparse tangent-instability cases.
Nonlinear and contact	EXPERIMENTAL or bounded	Newton, load-control, Arc-Length and contact paths remain route-specific.
Large model	SUPPORTED_WITH_LIMITATIONS	PETSc/MPI for recorded structured TET4 workloads; SciPy is for small or intermediate cases.

Optional PETSc/MPI route

PETSc and MPI are optional integrations. The large-model route uses a distributed AIJ matrix with structured diagonal/off-diagonal preallocation on the recorded qualification path. Its 1M, 3M, 5M and bounded 10M results apply only to the declared workloads, host and configuration. They are not a general HPC or GPU claim.

Public API

New applications should import from qf_solver and use the documented CLI qf-solver. The compatibility namespace solveur and legacy entry points are retained for existing integrations; see the API stability contract.