ANYsolver finite-element solver

anysolver is a headless structural FE solver for beam, shell, stiffened-panel, and cylindrical-shell analysis. It is an engineering solver with an explicit qualification scope, not a general-purpose CAD, contact, or fracture platform.

Install the released package with:

python -m pip install ANYsolver

For coordinated local development across sibling repositories, install the checkouts first:

python -m pip install -e C:\Github\ANYmaterial
python -m pip install -e C:\Github\ANYmesh
python -m pip install -e C:\Github\ANYfileIO
python -m pip install -e C:\Github\ANYsolver

Release order for the 0.4 line

ANYsolver 0.4 depends on compatible extracted packages. Publish them to the same target index in this order:

1. ANYmaterial and ANYmesher (either order).
2. ANYfileio, which depends on both.
3. ANYsolver 0.4.x, which depends on all three.

Apply that order separately to TestPyPI and PyPI. The compatible sibling releases are available on PyPI. The publish workflow checks the selected target index and refuses to build or upload ANYsolver unless ANYmaterial>=0.1,<0.2, ANYmesher>=0.1,<0.4, and ANYfileio>=0.1,<0.3 can already be resolved there. CI also uses pinned sibling source checkouts to exercise the exact compatibility graph.

ANYsolver uses the neutral mesh, panel-generation, quality, and section APIs available in ANYmesher 0.1 and retains compatibility through the additive 0.3 line. The strict <0.4 cap prevents an unqualified major contract change. The endpoint compatibility job exercises pinned 0.1.0 and 0.2.1 installed wheels on Windows AMD64 CPython 3.13; that focused job is not a wider platform or interpreter qualification claim.

Core analyses and the solver-owned generated-geometry workflow are available directly from anysolver; the lightweight normalized flat-panel and cylinder facade is exposed through anysolver.runtime:

from anysolver import (
    FEModel,
    GeneratedGeometryFEMConfig,
    LoadCase,
    run_generated_geometry_fem,
    solve_linear,
)
from anysolver.runtime import (
    LightweightFEMConfig,
    resolve_runtime_analysis,
    run_production_fem,
)

The runtime facade applies its normalized axial force, bending moment, shear force, torsional moment, and pressure inputs to the generated model. Set LightweightFEMConfig.follower_pressure=True only for nonlinear static or arc-length analysis using the static only or nonlinear static runtime path; incompatible linear, stepwise eigenvalue-buckling, transient, collision, and structured-capacity paths return an explicit invalid_follower_pressure status. Arc length retains the requested von Karman or corotational kinematics. Production runtime failures remain failures rather than being replaced by an estimator.

Application integrations should use resolve_runtime_analysis(config) to reflect the solver's effective nonlinear/material/control/kinematics choices; the normalization helpers with leading underscores are implementation details.

The generic GeneratedGeometryFEM* names are the preferred workflow API. Historical AnyStructureFEM* aliases remain available only for downstream compatibility. Material selection is owned by ANYmaterial; the root-level dnv_c208_steel_properties() and dnv_c208_steel_curve() names are temporary compatibility imports over its canonical table and validation.

The source code and tests are authoritative. Generated reports under reports/ are dated evidence snapshots and must be regenerated after solver changes before making release claims.

Functional overview

Production four-node shell selectors use the qualified E4-PL formulation by default. New/current-policy three-node shell selectors use the independently qualified E4-PL S3 V2D companion; historical S3 records without formulation authority remain explicit legacy. TRI6, Q8, and Q8R remain on their established implementations.

Qualified S3 admission intentionally fails closed where a triangle touches a shell edge with more than two incident elements. Automatically imprinted four-way sheet intersections therefore require junction-aware meshing support or an explicit model-level legacy-S3 rollback; the mesher never silently changes the formulation. The explicit legacy-Q4 rollback is deprecated during the 0.4.x burn-in and is scheduled for removal no earlier than 0.5.0; see the E4-PL migration guide for diagnostics, rollback, and release gates.

StructuralMaterial is a runtime-checkable, ANYmaterial-owned protocol containing name, density, elastic_symmetry, and elastic_compliance_matrix() in engineering Voigt order [11, 22, 33, 23, 13, 12]. FEModel.register_material() accepts compatible external objects through that contract; FEModel.add_orthotropic_material() constructs the canonical OrthotropicMaterial.

ANYmesher owns neutral mesh topology, numbering, quality and coupling records; this package converts them into solver elements and exact constraints. ANYfileio owns SESAM and CalculiX syntax; this package converts neutral records to FEModel objects and retains execution and validation evidence.

Every production solver uses the same fixed/MPC preflight. Invalid or cyclic systems fail before assembly or factorization. Linear, modal, buckling, nonlinear, arc-length, transient, and impact results include a normalized constraint residual diagnostic. Modal and buckling modes correctly verify the homogeneous variation equations when the base model has prescribed offsets.

ResourceConfig(solver_threads=N, assembly_threads=M) now applies scoped native and Numba limits. Native pools are restored even after exceptions, and parallel Numba assembly suppresses nested BLAS/OpenMP pools to one thread. Diagnostics record requested limits, active runtime pools, the selected sparse backend, and any limiter/backend fallback. Omitting the resource policy retains the backend's existing unrestricted default.

GeneralizedShellSectionProtocol and GeneralizedBeamSectionContract are likewise solver-owned structural interfaces. The built-in GeneralizedShellSection(A, B, D, As, ...) accepts pre-integrated laminate or homogenized shell stiffness, while GeneralizedBeamSection(stiffness, ...) accepts a coupled 6x6 sectional law. They may be attached directly to elements or supplied inline/by name through generated geometry. Optional section mass data override the legacy homogeneous mass construction; otherwise the attached material, thickness, and legacy section geometry continue to define mass.

For shells, material_direction is projected into the shell plane and then material_angle_deg is applied right-handed about the positive shell normal; without a direction, the angle starts at shell-local x. For beams, material axes 1/2/3 are beam-local x/y/z. Orthotropic beam sections must provide a positive cross_section["torsional_rigidity"] in N*m^2; isotropic beams retain G*J.

Implemented does not automatically mean qualified for every geometry or load regime. The live capability matrix is produced by write_production_readiness_artifacts() and the verification manifest.

Production scope

The qualified target is thin flat or cylindrical shell structure, with beam stiffeners/girders represented through the documented coupling, inside the verified mesh, material, distortion, eccentricity, and load ranges.

Important limits:

• no arbitrary CAD topology or automatic general-purpose meshing;
• no arbitrary 3-D anisotropic material law, ply-stack integration, ply stress recovery, tension/compression-asymmetric composite failure, or progressive composite damage. Pre-integrated linear shell A/B/D/As and beam 6x6 section laws are supported, including their elastic couplings;
• Q8R is experimental: its hourglass stabilization is not qualified for thin bending and it is deliberately excluded from nonlinear batch acceleration;
• the 3-node quadratic beam is straight-sided; curved members must be represented by straight beam segments until a true curved formulation is implemented;
• the shell initial-stress operator covers the in-plane N, M, and H stress moments acting on Mindlin midsurface translations and director gradients; it does not add drilling, transverse-normal-stress, or a geometrically exact finite-rotation shell/director formulation;
• current-area follower pressure is supported in nonlinear static and arc-length analyses, with its exact load tangent. Linear/dead pressure remains the default. Linear buckling rejects a constrained nonsymmetric follower-pressure pencil because general complex nonconservative eigenanalysis is not implemented;
• no general shell-shell, body-body, frictional, rolling, or self-contact;
• no fluid-structure interaction, cavitation, or water-entry model;
• no cohesive cracks, remeshing, material separation, or fracture-mechanics claim—the erosion models are engineering screens;
• no unrestricted deep post-buckling or automatic bifurcation branch switching;
• the consistent corotational tangent includes frame derivatives and is selected automatically for follower pressure, but its numerical frame-sensitivity evaluation is costlier than the rotated tangent used by default for ordinary corotational solves;
• material-history-aware recovery requires retained, matching committed nonlinear layer/fiber states; missing or invalid state is reported and the affected components fall back explicitly to elastic reconstruction;
• for legacy isotropic plastic histories, von_mises retains the established return-mapped shell in-plane or beam-fiber scope. Orthotropic results keep von_mises as the conventional invariant of the physical stress, including matching elastic transverse shear/torsion reconstruction, while equivalent_stress and hill_utilization remain explicitly scoped to the Hill-return-mapped components. mixed_reconstruction_von_mises and recovery provenance identify that mixed constitutive scope;
• the guarded patch-recovery fit is qualified only for locally planar, consistently oriented, homogeneous, full-integration Q4 or Q8 shell neighborhoods. Discontinuities remain separate, and the optional normalized stress-L2 discrepancy is a diagnostic—not an energy-norm error estimate;
• initial stress/prestrain fields are qualified only in element-local reference coordinates with kinematics="von_karman". Shell fields use the documented membrane/positive-face-bending convention, and beam fields require a configured fiber section. Input stress must be admissible for the supplied hardening state; equilibration may redistribute it and does not reconstruct the manufacturing history. A field-bearing restart also requires its matching converged displacement vector;
• the analytical plane-stress tangent is branch-consistent. The numerical derivative remains an oracle and automatic invalid-row fallback; local yield-residual nonconvergence fails closed;
• no unverified material laws or distortion ranges;
• orthotropic and generalized-section shells use the general element/nonlinear paths and report deterministic fallback diagnostics; generalized beams use the general element path, while the existing accelerated shell kernels remain isotropic homogeneous-section only;
• generalized-section recovery is resultants-only. CalculiX export rejects these sections because the current deck mapping cannot preserve their coupling; use analytical or a dedicated section-capable reference model;
• SESAM FEModel export remains outside the supported interchange gate;
• CalculiX comparison requires a compatible local executable and an explicit execution request. Deck generation alone is a reproducibility handoff, not external numerical evidence.

Use validate_production_model(), the analysis-specific preflight checks, and the generated production-scope artifacts before production use.

Documentation map

• ARCHITECTURE.md: package boundaries, analysis flow, and invariants.
• THEORY.md: implemented formulations and validity limits.
• ARC_LENGTH.md: continuation controls and use.
• NONLINEAR_PERFORMANCE.md: nonlinear assembly, sparse backend, threading, and diagnostics.
• QUALITY_CONTROL.md: verification commands, evidence hierarchy, and current checked status.
• reference_cases/README.md: local CalculiX/PrePoMax reference-case layout.
• MIGRATION.md: source provenance, inclusion boundary, and import changes.
• extract_mat_mesh_io_performance_review.md: current extraction, assembly, nonlinear, MPC and buckling performance evidence.

Basic verification

From the repository root:

python -m pytest tests -q -p no:cacheprovider
python run_qc.py --no-save
python scripts/run_fe_verification.py

The last command regenerates the canonical JSON and Markdown evidence under reports/verification/. Its default external-reference mode generates handoff decks with status not_executed; that status is not a pass or a claim of numerical agreement. To execute the comparisons, provide a compatible CalculiX executable on PATH, through ANYSOLVER_CALCULIX_EXECUTABLE, or with --calculix, and run:

python scripts/run_fe_verification.py --execute-calculix

An external case becomes passing evidence only after isolated execution, successful FRD/DAT parsing, and every declared comparison meeting its tolerance.

License

Starting with version 0.4.0, this project is licensed under the Mozilla Public License 2.0. See LICENSE for the full terms and LICENSING.md for the transition and third-party scope.

Earlier published versions remain available under the licence terms that applied to those versions.