FEM Study Defaults¶

Python API¶

The complete runnable example is in the numbered example section below; the exact callable fields and arguments are in the numbered API section. These values are copied from the current Python contract, not inferred from the UI.

Symbols and SI units¶

All geometric lengths use \(\mathrm{m}\); dimensionless selectors use \(1\).

Assumptions and validity¶

Authoring validation does not prove mesh generation or solver qualification; the realized report is authoritative.

1. What it is and when to use it¶

FEM stores study-level finite-element defaults. Use it as the lowest- precedence FEM policy; explicit object recipes, airbox settings, and workflow overrides take precedence where defined.

2. Physical and mathematical explanation¶

This is an authoring policy and introduces no new physical equation. order and maximum_element_size select the finite-element approximation and global target; demag_solver_policy configures the algebraic solve separately.

3. Example - complete Python script¶

# %% FEM study defaults through the stage-first builder
import fullmag as fm

nm = 1.0e-9
study = fm.study("fem_study_defaults")
study.engine("fem")
study.device("cpu", precision="double")
study.mode("strict")
study.objects.mesh.defaults(order=1, maximum_element_size=20 * nm)
body = study.geometry(fm.Box(80 * nm, 40 * nm, 4 * nm), name="film")
body.Ms = 800.0e3
body.Aex = 13.0e-12
body.m = fm.texture.uniform(1.0, 0.0, 0.0)
study.exchange()
study.demag(realization="poisson_robin")
study.build_domain_mesh()
study.stages.add_relax(
    stage_id="equilibrium",
    algorithm="llg_overdamped",
    tolA=1.0e-4,
    max_steps=1_000,
)

4. Exact API¶

Supplying both size aliases requires equal values; missing size, booleans, or invalid order fail during construction. Solver policy is serialized separately from mesh geometry.

ProblemIR¶

The request lowers to the mesh-workflow or discretization subtree; requested intent remains distinct from the resolved mesh asset and provenance report.

Round-trip and failure semantics¶

Requested intent is the Python policy; resolved execution is the realized mesh report. Validation errors identify the violated domain rule, and unsupported combinations fail explicitly without silent fallback.

Discrete realization¶

The backend consumes the realized Cartesian or finite-element asset, including topology, markers, quality, and provenance where available.

5. How to set it in Control Room¶

Route: Model Explorer -> Study -> Discretization -> FEM defaults. Set global order and maximum element size, press Apply, then Build Shared-Domain Mesh. Object and airbox overrides are edited in their own Mesh panels. not implemented: frontend support for low-level FEM(mesh=...) or solver-policy fields not rendered by the study editor. See Control Room capability register.

6. Backend and frontend support¶

Validation¶

Focused constructor, lowering, and mesh-report tests are the evidence boundary for this page.

7. Limitations and known pitfalls¶

• Study defaults have lower precedence than explicit object/workflow policies.

• hmax is an alias, not a second independent value.

• A policy object does not materialize or qualify a mesh by itself.

8. Scientific bibliography¶

1. P. G. Ciarlet, The Finite Element Method for Elliptic Problems, SIAM, 2002.

2. C. Geuzaine and J.-F. Remacle, “Gmsh: a three-dimensional finite element mesh generator,” International Journal for Numerical Methods in Engineering 79, 1309-1331 (2009), doi:10.1002/nme.2579.

9. Source-code index¶

Source-code index¶

• Python contract source: packages/fullmag-py/src/fullmag/model/discretization.py and packages/fullmag-py/src/fullmag/world.py, where applicable. Backend realization is in the relevant backends/fdm or backends/fem lane named by the page.