LLG¶

Last changes: 23:47 29.08.2026Documentation changelog

Contract¶

This page records the current public Python authoring contract and canonical lowering; it does not redefine solver physics.

Governing equations¶

This API page introduces no independent governing equation. Physical equations belong to interaction and solver-lane pages.

Symbols and SI units¶

Every owned input has its SI unit below; \(1\) denotes dimensionless data.

Assumptions and validity¶

Constructor checks run immediately. Lowering and planning additionally check mesh cardinality, capability, and backend legality.

Python API¶

Python	Type	Default	SI unit	Validation	Meaning	Backend support	ProblemIR
`LLG.gamma`	`float`	`221100.0`	\(\mathrm{m\,A^{-1}\,s^{-1}}\)	Positive finite gyromagnetic ratio used by the H-field LLG convention.	Positive finite gyromagnetic ratio used by the H-field LLG convention.	FEM/FDM CPU/GPU; planner checks combinations	`study.dynamics.gamma`
`LLG.integrator`	`str`	`"auto"`	\(1\)	Canonical supported integrator identifier or `auto`; planner and runtime legality are validated explicitly.	Canonical supported integrator identifier or `auto`; planner and runtime legality are validated explicitly.	FEM/FDM CPU/GPU; planner checks combinations	`study.dynamics.integrator`
`LLG.fixed_timestep`	`float \| None`	`None`	\(\mathrm{s}\)	Positive fixed step when supplied; mutually constrained with adaptive stepping.	Positive fixed step when supplied; mutually constrained with adaptive stepping.	FEM/FDM CPU/GPU; planner checks combinations	`study.dynamics.fixed_timestep`
`LLG.adaptive_timestep`	`AdaptiveTimestep \| None`	`None`	\(1\)	Optional adaptive-step contract.	Optional adaptive-step contract.	FEM/FDM CPU/GPU; planner checks combinations	`study.dynamics.adaptive_timestep`
`LLG.field_refresh`	`FieldRefreshPolicy \| None`	`None`	\(1\)	Optional field-refresh policy.	Optional field-refresh policy.	FEM/FDM CPU/GPU; planner checks combinations	`study.dynamics.field_refresh`

Complete stage-first example¶

The executable public form configures the LLG policy on study.solver(...). The constructor LLG(...) is not a standalone simulation workflow.

# %% LLG policy in a complete stage-first study
import fullmag as fm

nm = 1.0e-9
study = fm.study("llg_api_example")
study.engine("fdm")
study.device("cpu", precision="double")
study.mode("strict")
study.exchange()
study.objects.mesh.defaults(cell_size=(2 * nm, 2 * nm, 5 * nm))
film = study.geometry(fm.Box(100 * nm, 20 * nm, 5 * nm), name="film")
film.Ms = 800.0e3
film.Aex = 13.0e-12
film.alpha = 0.02
film.m = fm.init.UniformMagnetization((1.0, 0.0, 0.0))
study.solver(
    integrator="rk45",
    adaptive_timestep=fm.AdaptiveTimestep(
        atol=1.0e-6,
        rtol=1.0e-3,
        dt_min=1.0e-15,
        dt_max=1.0e-12,
    ),
    gamma=2.211e5,
)
study.stages.add_run(stage_id="run", until=1.0e-9)

ProblemIR¶

The final column gives the serialized destination owned by the current lowering implementation.

Round-trip and failure semantics¶

Requested intent is preserved in Python and IR. Resolved execution is selected by the planner. Validation errors reject malformed values; unsupported combinations fail capability checks without silent fallback.

Discrete realization¶

This page owns authoring and lowering only; numerical realization belongs to solver-lane documentation.

Implementation mapping¶

The adjacent map anchors claims to packages/fullmag-py/src/fullmag/model/dynamics.py and class LLG.

Validation¶

Tests compare this inventory with live signatures and validate its source map.

Limitations¶

Representability does not prove every backend combination executable; planner capabilities are authoritative.

Scientific bibliography¶

No physical model is introduced. Primary references belong to consuming interaction pages.

Control Room crosswalk¶

Status: Common solver/stage fields are partial; backend-specific options without editor fields remain not implemented.

Python/API surface	Control Room path	Status	Transaction
Parameters documented on this page	`Model Explorer -> Stages -> <stage> -> Solver`	`partial`	Apply stage draft; solver request and result resources become stale
Parameters without a named UI field	`Model Explorer -> Stages -> <stage> -> Solver`	`not implemented`	Python-only until implemented

frontend support is not implemented for dynamics parameters not rendered by the stage editor. See Control Room capability register for the support matrix and not implemented policy. Frontend source owner: apps/control-room/src/modules/inspector/panels/StudyStageDraftEditor.tsx (StudyStageDraftEditor).

Source-code index¶

Claim	Path	Stable symbol	Responsibility	Evidence
Constructor, validation, lowering	`packages/fullmag-py/src/fullmag/model/dynamics.py`	`class LLG`	Canonical Python API behavior	Ownership test and source-map validator