Solvers and backends

The route, element, formulation and evidence boundary determine which solver path is supported. Method names are not convergence guarantees; inspect the residual, conditioning, warnings and final diagnostics for every calculation. This page describes the bounded solver and backend scope of release 0.2.11.

Analysis / backend	Status	Scope
Linear static	QUALIFIED_BOUNDED	Direct and iterative sparse routes only within the recorded element-analysis matrix.
Modal	Route-dependent	Sparse eigenvalue routes for recorded bounded cases; mass and family scope vary.
Rotating modal	EXPERIMENTAL	Serial dense generalized QEP with scipy.linalg.eig(A, B); explicit complex spectrum, mass normalization and original-polynomial residuals. Not interchangeable with classical eigh/eigsh.
Campbell	EXPERIMENTAL	Multiple bounded rotating solves plus complex-MAC global assignment and subspace-aware tracking. Unresolved matches remain ambiguous, including the high-frequency pair at 100 rad/s.
Newmark / harmonic	Route-dependent; selected mixed routes EXPERIMENTAL_BOUNDED	Linear analysis and documented timestep/frequency/damping limits only.
Linear buckling	Route-dependent	Bounded first-factor cases; no postbuckling or bifurcation claim.
Nonlinear Newton	Bounded route evidence	Shared Newton/assembly/state infrastructure in selected material/geometric routes; not a general nonlinear solver claim.
Arc-length	Experimental bounded evidence	Specialized correction route; no general limit-point or postbuckling claim.
Frictionless contact	EXPERIMENTAL_BOUNDED	Bounded penalty node-to-triangle route.
Frictional contact	Prior bounded Owner acceptance; current-source formal requalification not established	Narrow serial stick/slip route with search and mesh-sensitivity limits.
Structured TET4 PETSc/MPI	Route-dependent historical evidence	Exact recorded workload, host and configuration only.
Two-rank PETSc/MPI linear static	Owner-accepted bounded evidence	One-element family cases, replicated input/root-side assembly; no scaling claim.
Mixed distributed PETSc/MPI runtime	NOT_VALIDATED	No generic mixed or nonlinear distributed runtime claim.

Optional PETSc/MPI

PETSc, MPI and SLEPc are optional integrations. The bounded two-rank acceptance does not establish distributed assembly, strong/weak scaling, nonlinear MPI, contact, dynamics or cross-family result equivalence. Historical structured TET4 large-model observations apply only to their exact configurations and environment. The standard installation uses SciPy and does not require these external runtimes.

The rotating QEP does not use these optional backends. Its initial method is dense_qep; Campbell uses complex_mac_hungarian for tracking, not a new physical solver. The dense characterization reached 1,000 physical DOFs on synthetic matrix pencils in the recorded environment, without extrapolation or a universal capacity promise. See rotating modal and Campbell for the full scope.

Public API

New applications should import from qf_solver and use the qf-solver CLI. The solveur compatibility namespace and legacy launchers remain during 0.2.x; the current compatibility plan targets removal of solveur-ef for 0.3.0. See the API stability contract and capability index.