Python API

`aquad.GLProductQuadrature1DSlab`	Gauss-Legendre quadrature for 1D, slab geometry.
`aquad.GLCProductQuadrature2DXY`	Gauss-Legendre-Chebyshev quadrature for 2D, XY geometry.
`aquad.GLCProductQuadrature3DXYZ`	Gauss-Legendre-Chebyshev quadrature for 3D, XYZ geometry.

aquad.GLCProductQuadrature2DRZ

Gauss-Legendre-Chebyshev product quadrature for 2D, RZ geometry.

Triangular quadrature

aquad.TriangularQuadrature

Triangular quadrature base class.

`aquad.GLCTriangularQuadrature2DXY`	Triangular Gauss-Legendre-Chebyshev quadrature for 2D, XY geometry.
`aquad.GLCTriangularQuadrature3DXYZ`	Triangular Gauss-Legendre-Chebyshev quadrature for 3D, XYZ geometry.

Lebedev quadrature

`aquad.LebedevQuadrature2DXY`	Lebedev quadrature for 2D, XY geometry.
`aquad.LebedevQuadrature3DXYZ`	Lebedev quadrature for 3D, XYZ geometry.

Simplified LDFES quadrature

`aquad.SLDFEsqQuadrature3DXYZ`	Piecewise-linear finite element quadrature using quadrilaterals.
`aquad.SLDFEsqQuadrature2DXY`	Two-dimensional variant of the piecewise-linear finite element quadrature.

Field functions

Base class

fieldfunc.FieldFunction

Field function.

Grid-based

fieldfunc.FieldFunctionGridBased

Field function grid based.

Interpolation

`fieldfunc.FieldFunctionInterpolation`	Base class for field-function interpolation objects.
`fieldfunc.FieldFunctionInterpolationPoint`	Interpolate the field function at a point.
`fieldfunc.FieldFunctionInterpolationLine`	Line based interpolation function.
`fieldfunc.FieldFunctionInterpolationVolume`	A line based interpolation function.

Mesh

mesh.MeshContinuum

Mesh continuum.

Surface mesh

mesh.SurfaceMesh

Surface mesh.

Mesh generator

mesh.MeshGenerator

Generic mesh generator.

`mesh.ExtruderMeshGenerator`	Extruded mesh generator.
`mesh.OrthogonalMeshGenerator`	Orthogonal mesh generator.
`mesh.FromFileMeshGenerator`	From file mesh generator.
`mesh.SplitFileMeshGenerator`	Split file mesh generator.
`mesh.DistributedMeshGenerator`	Distributed mesh generator.

Graph partitioner

mesh.GraphPartitioner

Generic graph partitioner.

`mesh.KBAGraphPartitioner`	Koch, Baker and Alcouffe based partitioning.
`mesh.LinearGraphPartitioner`	Basic linear partitioning.
`mesh.PETScGraphPartitioner`	PETSc based partitioning.

Logical volume

Base class

logvol.LogicalVolume

Generic logical volume.

Logical volume types

`logvol.BooleanLogicalVolume`	Boolean logical volume.
`logvol.RCCLogicalVolume`	Right circular cylinder logical volume.
`logvol.RPPLogicalVolume`	Rectangular parallel piped logical volume.
`logvol.SphereLogicalVolume`	Spherical logical volume.
`logvol.SurfaceMeshLogicalVolume`	Surface mesh logical volume.

Response evaluator

response.ResponseEvaluator

Response evaluator by folding sources against adjoint solutions.

Source

`source.PointSource`	Point sources, defined by its location and a group-wise strength vector.
`source.VolumetricSource`	Multi-group isotropic volumetric sources.

Cross section

xs.MultiGroupXS

Multi-group cross section.

Problem

Note

Forward/adjoint mode transitions are destructive by design. In Python there are three valid ways to set mode:

Set options={'adjoint': ...} in the problem constructor.
Call problem.SetOptions(adjoint=...).
Call problem.SetAdjoint(...) (low-level equivalent).

A mode transition triggers:

reinitializes material mode (forward vs adjoint),
clears point and volumetric sources,
clears boundary conditions,
zeros scalar and angular flux state.

The block-id to cross-section map is preserved. After switching mode, reapply the desired driving terms (sources and boundaries) before solving.

SetOptions is additive: only explicitly supplied options are updated. If adjoint is omitted in a SetOptions call, the current mode is unchanged.

Adjoint mode is applied to the mapped MultiGroupXS objects themselves. If the same cross-section object is shared across multiple problems, toggling adjoint mode in one problem affects all problems using that object.

Base class

`solver.Problem`	Base class for all problems.
`solver.LBSProblem`	Base class for all linear Boltzmann problems.

Discrete ordinates problem

Note

Steady-state <-> transient mode transitions are non-destructive for problem setup. Calling SetTimeDependentMode() or SetSteadyStateMode() preserves:

mesh and discretization,
block-id to cross-section mapping,
boundary conditions and source definitions,
scalar flux moments (phi_new/phi_old state).

For SetTimeDependentMode(), OpenSn needs angular fluxes (psi) for the transient RHS time term. Mode transition behavior is as follows:

If save_angular_flux is already enabled: - the mode switch performs internal transient mode configuration only.
If save_angular_flux is disabled: - OpenSn enables angular flux storage, - caches the scalar flux and performs a sweep to reconstruct psi, - restores the cached scalar flux, - completes internal transient mode configuration.

For SetSteadyStateMode(), transient-only internals are reset. If angular flux saving had been temporarily forced for transient use, the original save_angular_flux user setting is restored.

Practical implication: - save_angular_flux=False is valid for steady-state solves that later

transition to transient; OpenSn will reconstruct psi needed by the transient solver by performing a fixed-point iteration on the lagged angular fluxes with phi/q held at the converged steady-state value.

Warning

Reconstructed angular flux (psi) is consistent with the converged scalar scalar flux moments, but it is not guaranteed to be identical to the angular flux that would have been available if save_angular_flux=True had been used during the steady-state solve. Small first-step transient differences can therefore appear, especially for problems with reflecting boundaries or lagged angular fluxes.

solver.DiscreteOrdinatesProblem

Base class for discrete ordinates problems in Cartesian geometry.

Discrete ordinates curvilinear problem

solver.DiscreteOrdinatesCurvilinearProblem

Base class for discrete ordinates problems in curvilinear geometry.

Solvers

Solver base class

solver.Solver

Base class for all solvers.

Steady state source solver

solver.SteadyStateSourceSolver

Steady state solver.

Transient solver

solver.TransientSolver

Transient solver.

Non-linear k-eigen

solver.NonLinearKEigenSolver

Non-linear k-eigenvalue solver.

Power iteration solver

solver.PowerIterationKEigenSolver

Power iteration k-eigenvalue solver.

Acceleration methods

Discrete ordinates k-eigen acceleration base class

solver.DiscreteOrdinatesKEigenAcceleration

Base class for discrete ordinates k-eigenvalue acceleration methods.

Discrete ordinates k-eigen acceleration

`solver.SCDSAAcceleration`	Construct an SCDSA accelerator for the power iteration k-eigenvalue solver.
`solver.SMMAcceleration`	Construct an SMM accelerator for the power iteration k-eigenvalue solver.

Settings

Important

Functions in this section are only available to the module mode. For the console mode, refer to opensn --help for more information.

Logs

`context.SetVerbosityLevel`	Set verbosity level (0 to 3).
`context.UseColor`	Enable/disable color output.
`context.EnablePETScErrorHandler`	Allow PETSc error handler.

Caliper configuration

`context.SetCaliperConfig`	Set configuration to the Caliper manager.
`context.EnableCaliper`	Start the Caliper manager and mark the program begin.

Argument vector

`context.InitializeWithArgv`	Overwrite OpenSn settings using `sys.argv`.
`context.Finalize`	Finalize OpenSn context.