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

Field functions returned by solver methods such as GetScalarFluxFieldFunction(...), CreateFieldFunction(...), and GetAngularFieldFunctionList(...) are snapshots of the solver state at the time of the call. To obtain field functions from a newer solver state, call the corresponding solver method again.

Field-function interpolators are configured by assigning a field function and any geometry- or operation-specific settings, then calling Execute(). Execute() rebuilds any required internal interpolation state each time it is called; no separate initialization step is required.

`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`	Volume 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. That means save_angular_flux=True must already be enabled on the problem.

For SetSteadyStateMode(), transient-only internals are reset, but the configured angular-flux storage setting is otherwise unchanged.

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.