Python API#

The MC/DC public API is centered on mcdc.Simulation. A simulation owns the model geometry and material, sources, tallies, settings, transport techniques, and runtime state needed for one calculation.

Build the model with the public objects listed below, attach its root cells, sources, and tallies to a simulation, and then visualize or run that simulation:

simulation = mcdc.Simulation(name="Example")
simulation.set_model([cell])
simulation.set_sources([source])
simulation.set_tallies([tally])
simulation.settings.N_particle = 10_000
simulation.run()

The complete public interfaces and additional examples are documented on each linked API page. For a task-oriented explanation of how these objects move through construction, compilation, execution, and output, see Simulation Lifecycle.

Simulation#

mcdc.Simulation

The complete model and configuration for one MC/DC calculation.

Model building blocks#

Materials#

Materials define the interaction data used by cells. Use mcdc.Material for continuous-energy transport and mcdc.MaterialMG for multigroup transport.

`mcdc.Material`	Continuous-energy particle-interaction properties assigned to simulation cells.
`mcdc.MaterialMG`	Multigroup neutron-interaction properties assigned to simulation cells.

Geometry#

Surfaces bound spatial regions, cells pair those regions with materials or universes, and universes and lattices organize repeated geometry.

`mcdc.Surface`	Geometric boundaries of simulation cells.
`mcdc.Cell`	Material- or universe-filled regions of the simulation geometry.
`mcdc.Universe`	Reusable collections of cells in the simulation geometry.
`mcdc.Lattice`	Repeated arrangements of universes in the simulation geometry.

Sources#

Sources describe the distribution of the initial particle population in the simulation.

mcdc.Source

Distributions of particles introduced into the simulation.

Tallies#

Tallies define the quantities to score and the filters over which those scores are accumulated.

mcdc.Tally

Quantities measured during the simulation.

Meshes#

Meshes provide spatial bins for mesh-filtered tallies and transport techniques.

`mcdc.MeshUniform`	Uniform spatial bins for simulation tallies and transport techniques.
`mcdc.MeshStructured`	Structured spatial bins for simulation tallies and transport techniques.

Configuration and execution#

Simulation settings#

Each mcdc.Simulation owns its settings at simulation.settings. Settings control particle histories, batches, random-number generation, transport modes, census times, particle banks, output, and GPU execution. Specialized modes are configured through methods such as simulation.settings.set_eigenmode(...) and simulation.settings.set_time_census(...). See mcdc.Simulation for the complete settings interface.

Transport techniques#

Transport techniques are configured directly on the simulation instance. See mcdc.Simulation for their signatures and examples.

Compiling and running#

Calling simulation.run() compiles the current Python object graph when needed, executes particle transport, and writes the configured output. simulation.visualize_model(...) similarly compiles when needed before rendering the model. Use simulation.compile() when an explicit compiled snapshot is required before either operation.

The internal compilation and packing stages are documented in Simulation Compilation and Runtime Data Layout.